使用SWT创建自定义按钮

public class ImageButton extends Canvas {
private int mouse = 0;
private boolean hit = false;

    public ImageButton(Composite parent, int style) {        super(parent, style);        this.addPaintListener(new PaintListener() { public void paintControl(PaintEvent e) {     switch (mouse) {     case 0:         // Default state         e.gc.drawString("Normal", 5, 5);         break;     case 1:         // Mouse over         e.gc.drawString("Mouse over", 5, 5);         break;     case 2:         // Mouse down         e.gc.drawString("Hit", 5, 5);         break;     } }        });        this.addMouseMoveListener(new MouseMoveListener() { public void mouseMove(MouseEvent e) {     if (!hit)         return;     mouse = 2;     if (e.x < 0 || e.y < 0 || e.x > getBounds().width  || e.y > getBounds().height) {         mouse = 0;     }     redraw(); }        });        this.addMouseTrackListener(new MouseTrackAdapter() { public void mouseEnter(MouseEvent e) {     mouse = 1;     redraw(); } public void mouseExit(MouseEvent e) {     mouse = 0;     redraw(); }        });        this.addMouseListener(new MouseAdapter() { public void mouseDown(MouseEvent e) {     hit = true;     mouse = 2;     redraw(); } public void mouseUp(MouseEvent e) {     hit = false;     mouse = 1;     if (e.x < 0 || e.y < 0 || e.x > getBounds().width  || e.y > getBounds().height) {         mouse = 0;     }     redraw();     if (mouse == 1)         notifyListeners(SWT.Selection, new Event()); }        });        this.addKeyListener(new KeyAdapter() { public void keyPressed(KeyEvent e) {     if (e.keyCode == 'r' || e.character == ' ') {         Event event = new Event();         notifyListeners(SWT.Selection, event);     } }        });    }}