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Semester 1/Programming 1/Java/examples/projects/chapter01/figures/Canvas.java
Executable file
230
Semester 1/Programming 1/Java/examples/projects/chapter01/figures/Canvas.java
Executable 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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* 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 2016.02.29
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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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private static Canvas canvasSingleton;
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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 Picture Demo", 500, 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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// ----- instance part -----
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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 backgroundColor;
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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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* 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 bgColor the desired background color of the canvas
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*/
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private Canvas(String title, int width, int height, Color bgColor)
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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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frame.setLocation(30, 30);
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canvas.setPreferredSize(new Dimension(width, height));
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backgroundColor = bgColor;
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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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* 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 color
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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(backgroundColor);
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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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* 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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* 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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* Set the foreground color of the Canvas.
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* @param newColor the new color 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(new Color(235, 25, 25));
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}
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else if(colorString.equals("black")) {
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graphic.setColor(Color.black);
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}
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else if(colorString.equals("blue")) {
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graphic.setColor(new Color(30, 75, 220));
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}
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else if(colorString.equals("yellow")) {
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graphic.setColor(new Color(255, 230, 0));
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}
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else if(colorString.equals("green")) {
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graphic.setColor(new Color(80, 160, 60));
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}
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else if(colorString.equals("magenta")) {
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graphic.setColor(Color.magenta);
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}
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else if(colorString.equals("white")) {
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graphic.setColor(Color.white);
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}
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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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* 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(Object shape : objects) {
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shapes.get(shape).draw(graphic);
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}
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canvas.repaint();
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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(backgroundColor);
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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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* 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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* 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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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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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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