drawpanapp.java

一个简单的画板应用程序

import java.io.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;

class DrawPan extends JPanel {
	private LinkedList drawAction = new LinkedList();

	public void save(String file) throws IOException {
		ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(
				file));
		oos.writeObject(drawAction);
		oos.close();
	}

	public void load(String file) throws IOException, ClassNotFoundException {
		ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file));
		drawAction = (LinkedList) ois.readObject();
		ois.close();
		repaint();

	}

	public void clear() {
		drawAction.clear();
		repaint();
	}

	public void paint(Graphics g) {
		super.paint(g);
		ListIterator iter = drawAction.listIterator();
		while (iter.hasNext()) {
			LinkedList ll = (LinkedList) iter.next();
			ListIterator iter2 = ll.listIterator();
			int x1 = -1, y1 = -1;
			while (iter2.hasNext()) {
				Point temp = ((Point) iter2.next());
				if (x1 != -1 || y1 != -1)
					g.drawLine(x1, y1, temp.x, temp.y);

				x1 = temp.x;
				y1 = temp.y;
			}
		}

	}

	public DrawPan() {
		drawAction.push(new LinkedList());
		this.addMouseMotionListener(new MouseMotionListener() {
			public void mouseDragged(MouseEvent e) {
				((LinkedList) (drawAction.getFirst())).push(e.getPoint());
				repaint();
			}

			public void mouseMoved(MouseEvent e) {
			}
		});
		this.addMouseListener(new java.awt.event.MouseListener() {
			public void mouseClicked(MouseEvent e) {
			}

			public void mouseEntered(MouseEvent e) {
			}

			public void mouseExited(MouseEvent e) {
			}

			public void mousePressed(MouseEvent e) {
				drawAction.push(new LinkedList());
			}

			public void mouseReleased(MouseEvent e) {
			}

		});
	}

}

public class DrawPanApp extends JFrame {
	DrawPan drawPan = new DrawPan();

	public DrawPanApp() {
		JMenuBar menuBar = new JMenuBar();
		JMenu menuFile = new JMenu("File");
		JMenu menuDrawPan = new JMenu("DrawPan");

		JMenuItem itemSave = new JMenuItem("Save");
		JMenuItem itemLoad = new JMenuItem("Load");
		JMenuItem itemQuit = new JMenuItem("Quit");

		JMenuItem itemClear = new JMenuItem("Clear");

		menuDrawPan.add(itemClear);

		menuFile.add(itemLoad);
		menuFile.add(itemSave);
		menuFile.add(new JSeparator());
		menuFile.add(itemQuit);

		itemQuit.addActionListener(new ActionQuit());
		itemSave.addActionListener(new ActionSave(this, drawPan));
		itemLoad.addActionListener(new ActionLoad(this, drawPan));
		itemClear.addActionListener(new ActionClear(drawPan));

		menuBar.add(menuFile);
		menuBar.add(menuDrawPan);
		this.setJMenuBar(menuBar);
		this.add("Center", drawPan);
	}

	class ActionQuit implements ActionListener {
		public void actionPerformed(ActionEvent e) {
			System.exit(0);
		}
	}

	class ActionClear implements ActionListener {
		DrawPan dP;

		public ActionClear(DrawPan dP) {
			this.dP = dP;
		}

		public void actionPerformed(ActionEvent e) {
			dP.clear();
		}
	}

	class ActionSave implements ActionListener {
		ObjectOutputStream oos;

		DrawPan dP;

		FileDialog d;

		public ActionSave(JFrame app, DrawPan dP) {
			this.dP = dP;
			d = new FileDialog(app, "What file do you want to Save?");
		}

		public void actionPerformed(ActionEvent e) {
			try {
				d.setFile("*.draw");
				d.setDirectory(".");
				d.setVisible(true);
				String file;
				if ((file = d.getFile()) != null) {
					dP.save(d.getDirectory()+file);
				}
			} catch (IOException err) {
				err.printStackTrace();
			}
		}
	}

	class ActionLoad implements ActionListener {
		ObjectInputStream ois;

		DrawPan dP;

		FileDialog d;

		public ActionLoad(JFrame app, DrawPan dP) {
			this.dP = dP;
			d = new FileDialog(app, "What file do you want to load?");
		}

		public void actionPerformed(ActionEvent e) {
			try {
				d.setFile("*.draw");
				d.setDirectory(".");
				d.setVisible(true);
				String file;
				if ((file = d.getFile()) != null)
					dP.load(d.getDirectory()+file);
			} catch (ClassNotFoundException err) {
				err.printStackTrace();
			} catch (IOException err) {
				err.printStackTrace();
			}
		}
	}

	public static void main(String[] args) {
		DrawPanApp drawPanApp = new DrawPanApp();
		drawPanApp.setSize(200, 200);
		drawPanApp.setVisible(true);
	}
}