Browse Source

picture adds

Kr Younger 5 years ago
parent
commit
d5b82f1440

Canvas.java → Picture/Canvas.java View File


Circle.java → Picture/Circle.java View File


+ 86
- 0
Picture/Picture.java View File

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+
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+/**
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+ * This class represents a simple picture. You can draw the picture using
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+ * the draw method. But wait, there's more: being an electronic picture, it
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+ * can be changed. You can set it to black-and-white display and back to
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+ * colors (only after it's been drawn, of course).
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+ *
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+ * This class was written as an early example for teaching Java with BlueJ.
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+ * 
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+ * @author  Michael Kölling and David J. Barnes
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+ * @version 1.1  (24 May 2001)
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+ */
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+public class Picture
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+{
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+    private Square wall;
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+    private Square window;
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+    private Triangle roof;
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+    private Circle sun;
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+
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+    /**
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+     * Constructor for objects of class Picture
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+     */
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+    public Picture()
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+    {
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+        // nothing to do... instance variables are automatically set to null
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+    }
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+
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+    /**
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+     * Draw this picture.
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+     */
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+    public void draw()
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+    {
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+        wall = new Square();
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+        wall.moveVertical(80);
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+        wall.changeSize(100);
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+        wall.makeVisible();
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+
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+        window = new Square();
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+        window.changeColor("black");
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+        window.moveHorizontal(20);
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+        window.moveVertical(100);
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+        window.makeVisible();
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+
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+        roof = new Triangle();
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+        roof.changeSize(50, 140);
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+        roof.moveHorizontal(60);
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+        roof.moveVertical(70);
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+        roof.makeVisible();
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+
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+        sun = new Circle();
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+        sun.changeColor("yellow");
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+        sun.moveHorizontal(180);
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+        sun.moveVertical(-10);
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+        sun.changeSize(60);
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+        sun.makeVisible();
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+    }
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+
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+    /**
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+     * Change this picture to black/white display
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+     */
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+    public void setBlackAndWhite()
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+    {
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+        if(wall != null)   // only if it's painted already...
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+        {
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+            wall.changeColor("black");
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+            window.changeColor("white");
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+            roof.changeColor("black");
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+            sun.changeColor("black");
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+        }
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+    }
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+
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+    /**
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+     * Change this picture to use color display
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+     */
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+    public void setColor()
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+    {
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+        if(wall != null)   // only if it's painted already...
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+        {
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+            wall.changeColor("red");
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+            window.changeColor("black");
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+            roof.changeColor("green");
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+            sun.changeColor("yellow");
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+        }
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+    }
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+
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+}

+ 44
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Picture/README.TXT View File

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+Project "picture"
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+Authors: Michael Kölling and David J. Barnes
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+
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+This project is part of the material for the book
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+
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+   Objects First with Java - A Practical Introduction using BlueJ
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+   David J. Barnes and Michael Kolling
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+   Pearson Education, 2002
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+
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+It is discussed in chapter 1.
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+    
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+This is a very simple project to demonstrate some characteristics of
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+objects.
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+
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+You can create various shapes, and you will see, if you do, that those
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+shapes are drawn on screen (in a window that we call the "canvas").
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+
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+You can then manipulate these objects: change their position, size and 
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+colour. Try it out: create a few different squares, triangles and circles.
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+
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+This project is designed as a first example of object-oriented programming.
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+It illustrates a number of concepts:
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+
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+ - a Java project (application) is a collection of classes
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+ - objects can be created from classes
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+ - from any one class, many objects may be created
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+ - objects have operations (methods)
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+ - operations can have parameters
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+ - parameters have types (at least String and int)
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+ - objects hold data (fields)
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+ - the operations and fields are common to all objects
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+ - the values stored in the fields can be different for each object
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+
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+The project also demonstrates
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+
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+ - BlueJ object creation
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+ - interactive method invocation
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+ - parameter passing
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+
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+A good second project to look at after this is "picture", which adds a class
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+to those ones in this project. That class (named "Picture") uses the shapes
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+to draw a picture. It can be used to experiment with coding.
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+
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+Michael Kölling, July 2000

Square.java → Picture/Square.java View File


Triangle.java → Picture/Triangle.java View File


+ 78
- 0
Picture/package.bluej View File

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+#BlueJ package file
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+dependency1.from=Circle
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+dependency1.to=Canvas
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+dependency1.type=UsesDependency
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+dependency2.from=Picture
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+dependency2.to=Square
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+dependency2.type=UsesDependency
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+dependency3.from=Picture
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+dependency3.to=Triangle
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+dependency3.type=UsesDependency
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+dependency4.from=Picture
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+dependency4.to=Circle
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+dependency4.type=UsesDependency
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+dependency5.from=Triangle
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+dependency5.to=Canvas
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+dependency5.type=UsesDependency
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+dependency6.from=Square
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+dependency6.to=Canvas
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+dependency6.type=UsesDependency
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+editor.fx.0.height=722
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+editor.fx.0.width=800
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+editor.fx.0.x=2086
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+editor.fx.0.y=284
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+objectbench.height=101
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+objectbench.width=461
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+package.divider.horizontal=0.6
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+package.divider.vertical=0.8007380073800738
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+package.editor.height=427
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+package.editor.width=674
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+package.editor.x=2011
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+package.editor.y=179
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+package.frame.height=600
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+package.frame.width=800
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+package.numDependencies=6
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+package.numTargets=5
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+package.showExtends=true
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+package.showUses=true
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+project.charset=UTF-8
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+readme.height=58
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+readme.name=@README
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+readme.width=47
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+readme.x=10
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+readme.y=10
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+target1.height=40
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+target1.name=Circle
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+target1.showInterface=false
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+target1.type=ClassTarget
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+target1.width=80
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+target1.x=110
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+target1.y=120
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+target2.height=40
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+target2.name=Picture
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+target2.showInterface=false
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+target2.type=ClassTarget
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+target2.width=80
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+target2.x=420
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+target2.y=160
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+target3.height=40
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+target3.name=Canvas
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+target3.showInterface=false
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+target3.type=ClassTarget
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+target3.width=80
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+target3.x=20
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+target3.y=180
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+target4.height=40
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+target4.name=Triangle
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+target4.showInterface=false
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+target4.type=ClassTarget
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+target4.width=80
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+target4.x=270
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+target4.y=60
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+target5.height=40
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+target5.name=Square
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+target5.showInterface=false
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+target5.type=ClassTarget
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+target5.width=80
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+target5.x=190
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+target5.y=90

+ 221
- 0
Shapes/Canvas.java View File

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+import javax.swing.*;
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+import java.awt.*;
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+import java.util.List;
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+import java.util.*;
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+
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+/**
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+ * Canvas is a class to allow for simple graphical drawing on a canvas.
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+ * This is a modification of the general purpose Canvas, specially made for
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+ * the BlueJ "shapes" example. 
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+ *
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+ * @author: Bruce Quig
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+ * @author: Michael Kölling (mik)
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+ *
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+ * @version: 1.6 (shapes)
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+ */
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+public class Canvas
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+{
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+    // Note: The implementation of this class (specifically the handling of
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+    // shape identity and colors) is slightly more complex than necessary. This
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+    // is done on purpose to keep the interface and instance fields of the
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+    // shape objects in this project clean and simple for educational purposes.
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+
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+    private static Canvas canvasSingleton;
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+
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+    /**
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+     * Factory method to get the canvas singleton object.
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+     */
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+    public static Canvas getCanvas()
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+    {
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+        if(canvasSingleton == null) {
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+            canvasSingleton = new Canvas("BlueJ Shapes Demo", 300, 300, 
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+                    Color.white);
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+        }
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+        canvasSingleton.setVisible(true);
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+        return canvasSingleton;
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+    }
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+
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+    //  ----- instance part -----
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+
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+    private JFrame frame;
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+    private CanvasPane canvas;
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+    private Graphics2D graphic;
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+    private Color backgroundColour;
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+    private Image canvasImage;
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+    private List<Object> objects;
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+    private HashMap<Object, ShapeDescription> shapes;
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+    
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+    /**
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+     * Create a Canvas.
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+     * @param title  title to appear in Canvas Frame
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+     * @param width  the desired width for the canvas
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+     * @param height  the desired height for the canvas
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+     * @param bgClour  the desired background colour of the canvas
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+     */
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+    private Canvas(String title, int width, int height, Color bgColour)
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+    {
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+        frame = new JFrame();
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+        canvas = new CanvasPane();
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+        frame.setContentPane(canvas);
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+        frame.setTitle(title);
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+        canvas.setPreferredSize(new Dimension(width, height));
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+        backgroundColour = bgColour;
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+        frame.pack();
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+        objects = new ArrayList<Object>();
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+        shapes = new HashMap<Object, ShapeDescription>();
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+    }
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+
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+    /**
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+     * Set the canvas visibility and brings canvas to the front of screen
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+     * when made visible. This method can also be used to bring an already
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+     * visible canvas to the front of other windows.
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+     * @param visible  boolean value representing the desired visibility of
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+     * the canvas (true or false) 
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+     */
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+    public void setVisible(boolean visible)
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+    {
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+        if(graphic == null) {
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+            // first time: instantiate the offscreen image and fill it with
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+            // the background colour
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+            Dimension size = canvas.getSize();
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+            canvasImage = canvas.createImage(size.width, size.height);
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+            graphic = (Graphics2D)canvasImage.getGraphics();
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+            graphic.setColor(backgroundColour);
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+            graphic.fillRect(0, 0, size.width, size.height);
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+            graphic.setColor(Color.black);
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+        }
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+        frame.setVisible(visible);
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+    }
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+
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+    /**
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+     * Draw a given shape onto the canvas.
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+     * @param  referenceObject  an object to define identity for this shape
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+     * @param  color            the color of the shape
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+     * @param  shape            the shape object to be drawn on the canvas
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+     */
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+     // Note: this is a slightly backwards way of maintaining the shape
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+     // objects. It is carefully designed to keep the visible shape interfaces
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+     // in this project clean and simple for educational purposes.
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+    public void draw(Object referenceObject, String color, Shape shape)
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+    {
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+        objects.remove(referenceObject);   // just in case it was already there
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+        objects.add(referenceObject);      // add at the end
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+        shapes.put(referenceObject, new ShapeDescription(shape, color));
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+        redraw();
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+    }
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+ 
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+    /**
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+     * Erase a given shape's from the screen.
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+     * @param  referenceObject  the shape object to be erased 
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+     */
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+    public void erase(Object referenceObject)
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+    {
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+        objects.remove(referenceObject);   // just in case it was already there
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+        shapes.remove(referenceObject);
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+        redraw();
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+    }
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+
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+    /**
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+     * Set the foreground colour of the Canvas.
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+     * @param  newColour   the new colour for the foreground of the Canvas 
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+     */
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+    public void setForegroundColor(String colorString)
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+    {
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+        if(colorString.equals("red"))
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+            graphic.setColor(Color.red);
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+        else if(colorString.equals("black"))
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+            graphic.setColor(Color.black);
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+        else if(colorString.equals("blue"))
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+            graphic.setColor(Color.blue);
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+        else if(colorString.equals("yellow"))
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+            graphic.setColor(Color.yellow);
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+        else if(colorString.equals("green"))
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+            graphic.setColor(Color.green);
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+        else if(colorString.equals("magenta"))
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+            graphic.setColor(Color.magenta);
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+        else if(colorString.equals("white"))
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+            graphic.setColor(Color.white);
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+        else
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+            graphic.setColor(Color.black);
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+    }
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+
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+    /**
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+     * Wait for a specified number of milliseconds before finishing.
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+     * This provides an easy way to specify a small delay which can be
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+     * used when producing animations.
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+     * @param  milliseconds  the number 
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+     */
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+    public void wait(int milliseconds)
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+    {
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+        try
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+        {
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+            Thread.sleep(milliseconds);
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+        } 
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+        catch (Exception e)
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+        {
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+            // ignoring exception at the moment
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+        }
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+    }
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+
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+    /**
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+     * Redraw ell shapes currently on the Canvas.
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+     */
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+    private void redraw()
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+    {
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+        erase();
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+        for(Iterator i=objects.iterator(); i.hasNext(); ) {
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+            ((ShapeDescription)shapes.get(i.next())).draw(graphic);
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+        }
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+        canvas.repaint();
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+    }
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+       
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+    /**
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+     * Erase the whole canvas. (Does not repaint.)
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+     */
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+    private void erase()
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+    {
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+        Color original = graphic.getColor();
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+        graphic.setColor(backgroundColour);
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+        Dimension size = canvas.getSize();
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+        graphic.fill(new Rectangle(0, 0, size.width, size.height));
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+        graphic.setColor(original);
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+    }
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+
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+
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+    /************************************************************************
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+     * Inner class CanvasPane - the actual canvas component contained in the
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+     * Canvas frame. This is essentially a JPanel with added capability to
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+     * refresh the image drawn on it.
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+     */
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+    private class CanvasPane extends JPanel
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+    {
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+        public void paint(Graphics g)
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+        {
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+            g.drawImage(canvasImage, 0, 0, null);
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+        }
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+    }
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+    
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+    /************************************************************************
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+     * Inner class CanvasPane - the actual canvas component contained in the
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+     * Canvas frame. This is essentially a JPanel with added capability to
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+     * refresh the image drawn on it.
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+     */
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+    private class ShapeDescription
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+    {
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+        private Shape shape;
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+        private String colorString;
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+
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+        public ShapeDescription(Shape shape, String color)
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+        {
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+            this.shape = shape;
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+            colorString = color;
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+        }
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+
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+        public void draw(Graphics2D graphic)
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+        {
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+            setForegroundColor(colorString);
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+            graphic.fill(shape);
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+        }
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+    }
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+
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+}

+ 192
- 0
Shapes/Circle.java View File

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+import java.awt.*;
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+import java.awt.geom.*;
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+
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+/**
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+ * A circle that can be manipulated and that draws itself on a canvas.
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+ * 
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+ * @author  Michael Kölling and David J. Barnes
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+ * @version 1.0  (15 July 2000)
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+ */
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+
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+public class Circle
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+{
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+    private int diameter;
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+    private int xPosition;
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+    private int yPosition;
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+    private String color;
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+    private boolean isVisible;
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+
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+    /**
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+     * Create a new circle at default position with default color.
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+     */
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+    public Circle()
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+    {
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+        diameter = 30;
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+        xPosition = 20;
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+        yPosition = 60;
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+        color = "blue";
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+        isVisible = false;
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+    }
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+
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+    /**
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+     * Make this circle visible. If it was already visible, do nothing.
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+     */
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+    public void makeVisible()
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+    {
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+        isVisible = true;
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+        draw();
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+    }
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+
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+    /**
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+     * Make this circle invisible. If it was already invisible, do nothing.
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+     */
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+    public void makeInvisible()
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+    {
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+        erase();
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+        isVisible = false;
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+    }
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+
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+    /**
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+     * Move the circle a few pixels to the right.
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+     */
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+    public void moveRight()
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+    {
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+        moveHorizontal(20);
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+    }
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+
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+    /**
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+     * Move the circle a few pixels to the left.
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+     */
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+    public void moveLeft()
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+    {
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+        moveHorizontal(-20);
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+    }
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+
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+    /**
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+     * Move the circle a few pixels up.
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+     */
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+    public void moveUp()
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+    {
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+        moveVertical(-20);
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+    }
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+
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+    /**
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+     * Move the circle a few pixels down.
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+     */
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+    public void moveDown()
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+    {
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+        moveVertical(20);
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+    }
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+
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+    /**
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+     * Move the circle horizontally by 'distance' pixels.
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+     */
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+    public void moveHorizontal(int distance)
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+    {
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+        erase();
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+        xPosition += distance;
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+        draw();
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+    }
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+
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+    /**
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+     * Move the circle vertically by 'distance' pixels.
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+     */
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+    public void moveVertical(int distance)
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+    {
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+        erase();
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+        yPosition += distance;
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+        draw();
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+    }
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+
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+    /**
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+     * Slowly move the circle horizontally by 'distance' pixels.
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+     */
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+    public void slowMoveHorizontal(int distance)
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+    {
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+        int delta;
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+
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+        if(distance < 0) 
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+        {
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+            delta = -1;
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+            distance = -distance;
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+        }
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+        else 
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+        {
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+            delta = 1;
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+        }
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+
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+        for(int i = 0; i < distance; i++)
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+        {
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+            xPosition += delta;
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+            draw();
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+        }
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+    }
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+
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+    /**
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+     * Slowly move the circle vertically by 'distance' pixels.
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+     */
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+    public void slowMoveVertical(int distance)
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+    {
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+        int delta;
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+
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+        if(distance < 0) 
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+        {
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+            delta = -1;
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+            distance = -distance;
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+        }
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+        else 
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+        {
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+            delta = 1;
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+        }
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+
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+        for(int i = 0; i < distance; i++)
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+        {
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+            yPosition += delta;
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+            draw();
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+        }
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+    }
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+
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+    /**
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+     * Change the size to the new size (in pixels). Size must be >= 0.
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+     */
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+    public void changeSize(int newDiameter)
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+    {
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+        erase();
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+        diameter = newDiameter;
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+        draw();
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+    }
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+
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+    /**
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+     * Change the color. Valid colors are "red", "yellow", "blue", "green",
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+     * "magenta" and "black".
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+     */
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+    public void changeColor(String newColor)
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+    {
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+        color = newColor;
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+        draw();
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+    }
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+
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+    /*
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+     * Draw the circle with current specifications on screen.
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+     */
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+    private void draw()
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+    {
174
+        if(isVisible) {
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+            Canvas canvas = Canvas.getCanvas();
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+            canvas.draw(this, color, new Ellipse2D.Double(xPosition, yPosition, 
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+                    diameter, diameter));
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+            canvas.wait(10);
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+        }
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+    }
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+
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+    /*
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+     * Erase the circle on screen.
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+     */
185
+    private void erase()
186
+    {
187
+        if(isVisible) {
188
+            Canvas canvas = Canvas.getCanvas();
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+            canvas.erase(this);
190
+        }
191
+    }
192
+}

README.TXT → Shapes/README.TXT View File


+ 11
- 0
Shapes/README.md View File

@@ -0,0 +1,11 @@
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+# FirstLab-Shapes
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+
3
+This is the first BlueJ lab. 
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+
5
+Be sure to 
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+
7
+* FORK it to your own account.
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+* CLONE your version of the repo into your dev directory.
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+* Open the BlueJ project file from Finder.
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+
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+Object of lb is to follow the chapter reading the doc folder. (Draw a House!)

+ 191
- 0
Shapes/Square.java View File

@@ -0,0 +1,191 @@
1
+import java.awt.*;
2
+
3
+/**
4
+ * A square that can be manipulated and that draws itself on a canvas.
5
+ * 
6
+ * @author  Michael Kölling and David J. Barnes
7
+ * @version 1.0  (15 July 2000)
8
+ */
9
+
10
+public class Square
11
+{
12
+    private int size;
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+    private int xPosition;
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+    private int yPosition;
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+    private String color;
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+    private boolean isVisible;
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+
18
+    /**
19
+     * Create a new square at default position with default color.
20
+     */
21
+    public Square()
22
+    {
23
+        size = 30;
24
+        xPosition = 60;
25
+        yPosition = 50;
26
+        color = "red";
27
+        isVisible = false;
28
+    }
29
+
30
+    /**
31
+     * Make this square visible. If it was already visible, do nothing.
32
+     */
33
+    public void makeVisible()
34
+    {
35
+        isVisible = true;
36
+        draw();
37
+    }
38
+
39
+    /**
40
+     * Make this square invisible. If it was already invisible, do nothing.
41
+     */
42
+    public void makeInvisible()
43
+    {
44
+        erase();
45
+        isVisible = false;
46
+    }
47
+
48
+    /**
49
+     * Move the square a few pixels to the right.
50
+     */
51
+    public void moveRight()
52
+    {
53
+        moveHorizontal(20);
54
+    }
55
+
56
+    /**
57
+     * Move the square a few pixels to the left.
58
+     */
59
+    public void moveLeft()
60
+    {
61
+        moveHorizontal(-20);
62
+    }
63
+
64
+    /**
65
+     * Move the square a few pixels up.
66
+     */
67
+    public void moveUp()
68
+    {
69
+        moveVertical(-20);
70
+    }
71
+
72
+    /**
73
+     * Move the square a few pixels down.
74
+     */
75
+    public void moveDown()
76
+    {
77
+        moveVertical(20);
78
+    }
79
+
80
+    /**
81
+     * Move the square horizontally by 'distance' pixels.
82
+     */
83
+    public void moveHorizontal(int distance)
84
+    {
85
+        erase();
86
+        xPosition += distance;
87
+        draw();
88
+    }
89
+
90
+    /**
91
+     * Move the square vertically by 'distance' pixels.
92
+     */
93
+    public void moveVertical(int distance)
94
+    {
95
+        erase();
96
+        yPosition += distance;
97
+        draw();
98
+    }
99
+
100
+    /**
101
+     * Slowly move the square horizontally by 'distance' pixels.
102
+     */
103
+    public void slowMoveHorizontal(int distance)
104
+    {
105
+        int delta;
106
+
107
+        if(distance < 0) 
108
+        {
109
+            delta = -1;
110
+            distance = -distance;
111
+        }
112
+        else 
113
+        {
114
+            delta = 1;
115
+        }
116
+
117
+        for(int i = 0; i < distance; i++)
118
+        {
119
+            xPosition += delta;
120
+            draw();
121
+        }
122
+    }
123
+
124
+    /**
125
+     * Slowly move the square vertically by 'distance' pixels.
126
+     */
127
+    public void slowMoveVertical(int distance)
128
+    {
129
+        int delta;
130
+
131
+        if(distance < 0) 
132
+        {
133
+            delta = -1;
134
+            distance = -distance;
135
+        }
136
+        else 
137
+        {
138
+            delta = 1;
139
+        }
140
+
141
+        for(int i = 0; i < distance; i++)
142
+        {
143
+            yPosition += delta;
144
+            draw();
145
+        }
146
+    }
147
+
148
+    /**
149
+     * Change the size to the new size (in pixels). Size must be >= 0.
150
+     */
151
+    public void changeSize(int newSize)
152
+    {
153
+        erase();
154
+        size = newSize;
155
+        draw();
156
+    }
157
+
158
+    /**
159
+     * Change the color. Valid colors are "red", "yellow", "blue", "green",
160
+     * "magenta" and "black".
161
+     */
162
+    public void changeColor(String newColor)
163
+    {
164
+        color = newColor;
165
+        draw();
166
+    }
167
+
168
+    /*
169
+     * Draw the square with current specifications on screen.
170
+     */
171
+    private void draw()
172
+    {
173
+        if(isVisible) {
174
+            Canvas canvas = Canvas.getCanvas();
175
+            canvas.draw(this, color,
176
+                    new Rectangle(xPosition, yPosition, size, size));
177
+            canvas.wait(10);
178
+        }
179
+    }
180
+
181
+    /*
182
+     * Erase the square on screen.
183
+     */
184
+    private void erase()
185
+    {
186
+        if(isVisible) {
187
+            Canvas canvas = Canvas.getCanvas();
188
+            canvas.erase(this);
189
+        }
190
+    }
191
+}

+ 195
- 0
Shapes/Triangle.java View File

@@ -0,0 +1,195 @@
1
+import java.awt.*;
2
+
3
+/**
4
+ * A triangle that can be manipulated and that draws itself on a canvas.
5
+ * 
6
+ * @author  Michael Kölling and David J. Barnes
7
+ * @version 1.0  (15 July 2000)
8
+ */
9
+
10
+public class Triangle
11
+{
12
+    private int height;
13
+    private int width;
14
+    private int xPosition;
15
+    private int yPosition;
16
+    private String color;
17
+    private boolean isVisible;
18
+
19
+    /**
20
+     * Create a new triangle at default position with default color.
21
+     */
22
+    public Triangle()
23
+    {
24
+        height = 30;
25
+        width = 40;
26
+        xPosition = 50;
27
+        yPosition = 15;
28
+        color = "green";
29
+        isVisible = false;
30
+    }
31
+
32
+    /**
33
+     * Make this triangle visible. If it was already visible, do nothing.
34
+     */
35
+    public void makeVisible()
36
+    {
37
+        isVisible = true;
38
+        draw();
39
+    }
40
+
41
+    /**
42
+     * Make this triangle invisible. If it was already invisible, do nothing.
43
+     */
44
+    public void makeInvisible()
45
+    {
46
+        erase();
47
+        isVisible = false;
48
+    }
49
+
50
+    /**
51
+     * Move the triangle a few pixels to the right.
52
+     */
53
+    public void moveRight()
54
+    {
55
+        moveHorizontal(20);
56
+    }
57
+
58
+    /**
59
+     * Move the triangle a few pixels to the left.
60
+     */
61
+    public void moveLeft()
62
+    {
63
+        moveHorizontal(-20);
64
+    }
65
+
66
+    /**
67
+     * Move the triangle a few pixels up.
68
+     */
69
+    public void moveUp()
70
+    {
71
+        moveVertical(-20);
72
+    }
73
+
74
+    /**
75
+     * Move the triangle a few pixels down.
76
+     */
77
+    public void moveDown()
78
+    {
79
+        moveVertical(20);
80
+    }
81
+
82
+    /**
83
+     * Move the triangle horizontally by 'distance' pixels.
84
+     */
85
+    public void moveHorizontal(int distance)
86
+    {
87
+        erase();
88
+        xPosition += distance;
89
+        draw();
90
+    }
91
+
92
+    /**
93
+     * Move the triangle vertically by 'distance' pixels.
94
+     */
95
+    public void moveVertical(int distance)
96
+    {
97
+        erase();
98
+        yPosition += distance;
99
+        draw();
100
+    }
101
+
102
+    /**
103
+     * Slowly move the triangle horizontally by 'distance' pixels.
104
+     */
105
+    public void slowMoveHorizontal(int distance)
106
+    {
107
+        int delta;
108
+
109
+        if(distance < 0) 
110
+        {
111
+            delta = -1;
112
+            distance = -distance;
113
+        }
114
+        else 
115
+        {
116
+            delta = 1;
117
+        }
118
+
119
+        for(int i = 0; i < distance; i++)
120
+        {
121
+            xPosition += delta;
122
+            draw();
123
+        }
124
+    }
125
+
126
+    /**
127
+     * Slowly move the triangle vertically by 'distance' pixels.
128
+     */
129
+    public void slowMoveVertical(int distance)
130
+    {
131
+        int delta;
132
+
133
+        if(distance < 0) 
134
+        {
135
+            delta = -1;
136
+            distance = -distance;
137
+        }
138
+        else 
139
+        {
140
+            delta = 1;
141
+        }
142
+
143
+        for(int i = 0; i < distance; i++)
144
+        {
145
+            yPosition += delta;
146
+            draw();
147
+        }
148
+    }
149
+
150
+    /**
151
+     * Change the size to the new size (in pixels). Size must be >= 0.
152
+     */
153
+    public void changeSize(int newHeight, int newWidth)
154
+    {
155
+        erase();
156
+        height = newHeight;
157
+        width = newWidth;
158
+        draw();
159
+    }
160
+
161
+    /**
162
+     * Change the color. Valid colors are "red", "yellow", "blue", "green",
163
+     * "magenta" and "black".
164
+     */
165
+    public void changeColor(String newColor)
166
+    {
167
+        color = newColor;
168
+        draw();
169
+    }
170
+
171
+    /*
172
+     * Draw the triangle with current specifications on screen.
173
+     */
174
+    private void draw()
175
+    {
176
+        if(isVisible) {
177
+            Canvas canvas = Canvas.getCanvas();
178
+            int[] xpoints = { xPosition, xPosition + (width/2), xPosition - (width/2) };
179
+            int[] ypoints = { yPosition, yPosition + height, yPosition + height };
180
+            canvas.draw(this, color, new Polygon(xpoints, ypoints, 3));
181
+            canvas.wait(10);
182
+        }
183
+    }
184
+
185
+    /*
186
+     * Erase the triangle on screen.
187
+     */
188
+    private void erase()
189
+    {
190
+        if(isVisible) {
191
+            Canvas canvas = Canvas.getCanvas();
192
+            canvas.erase(this);
193
+        }
194
+    }
195
+}

doc/BlueJ-objects-first-ch1.pdf → Shapes/doc/BlueJ-objects-first-ch1.pdf View File


package.bluej → Shapes/package.bluej View File