Horizontal Scroll Bar Implementation On J2ME

一个提问

按照回帖的方法从google cache获取的solution页面

下面是代码：

MIDlet

public class Scroller extends MIDlet implements CommandListener
{
    private Display display;
    private Command exitCommand;
    private Command viewCommand;
    private Form mainForm;
    private ScrollCanvas scrollCanvas;
   
    public Scroller()
    {
        exitCommand = new Command("Exit", Command.EXIT, 1);
        viewCommand = new Command("View", Command.SCREEN, 1);
       
        mainForm = new Form("Scroller");
        mainForm.append("Press 'View' to access the scrolling image");
        mainForm.addCommand(viewCommand);
        mainForm.addCommand(exitCommand);
        mainForm.setCommandListener(this);
       
        scrollCanvas = new ScrollCanvas();
        scrollCanvas.addCommand(exitCommand);
        scrollCanvas.setCommandListener(this);
    }
   
    public void startApp()
    {
        display = Display.getDisplay(this);
        display.setCurrent(mainForm);
    }
   
    public void pauseApp()
    {
    }
   
    public void destroyApp(boolean flag)
    {
    }
   
    public void commandAction(Command command, Displayable displayable)
    {
        if (command == viewCommand)
        {
            display.setCurrent(scrollCanvas);
        }
        else if (command == exitCommand)
        {
            destroyApp(true);
            notifyDestroyed();
        }
    }
}

Canvas

public class ScrollCanvas extends Canvas
{
    private static final int TOP_LEFT = Graphics.TOP | Graphics.LEFT;
    private Image bigImage;
    private int imgX;
    private int imgY;
   
    public ScrollCanvas()
    {
        try
        {
            bigImage = Image.createImage("/images/myImg.png");
        }
        catch (IOException ioe)
        {
            // Deal with failure to load image.
        }
    }
   
    public void paint(Graphics graphics)
    {
        graphics.setColor(0x000000);
        graphics.fillRect(0, 0, getWidth(), getHeight());
        graphics.drawImage(bigImage, imgX, imgY, TOP_LEFT);
    }
   
    public void keyReleased(int keyCode)
    {
        int gameKey = getGameAction(keyCode);

        if ((gameKey == UP) || (keyCode == KEY_NUM2))
        {
            imgY++;
        }
        else if ((gameKey == LEFT) || (keyCode == KEY_NUM4))
        {
            imgX++;
        }
        else if ((gameKey == RIGHT) || (keyCode == KEY_NUM6))
        {
            imgX--;
        }
        else if ((gameKey == DOWN) || (keyCode == KEY_NUM8))
        {
            imgY--;
        }

        repaint();
        serviceRepaints();
    }
}