Question

我用Java创建了一个允许拖动两个椭圆形状的程序。现在我想将其转换为JApplet，因此我将类扩展为JApplet而不是原始JPanel。这个问题是super.paintComponent(g)不起作用，因为它不再是父类。

我尝试在类中创建JPanel然后引用此但我收到错误：类型paintComponent(Graphics)中的方法JComponent不可见

任何关于我需要做什么或任何帮助的人都会非常感谢。

这是我的代码。

public class Main extends JPanel 
{
    private static final String TITLE = "Drag me!";
    private static final int W = 640;
    private static final int H = 480;
    private Point origin = new Point(W / 2, H / 2);
    private Point mousePt;
    public Main() {

    this.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
    this.addMouseListener(new MouseAdapter() 
    {
            @Override
            public void mousePressed(MouseEvent e) 
            {
                mousePt = e.getPoint();
                repaint();
            }
        });
    this.addMouseMotionListener(new MouseMotionAdapter() 
    {
            @Override
            public void mouseDragged(MouseEvent e) 
            {
                int dx = e.getX() - mousePt.x;
                int dy = e.getY() - mousePt.y;
                origin.setLocation(origin.x + dx, origin.y + dy);
                mousePt = e.getPoint();
                repaint();
            }
    });
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(W, H);
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawOval(0, origin.y, getWidth(), origin.y);
        g.drawOval(origin.x, 0, origin.x, getHeight());
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame f = new JFrame(TITLE);
                f.add(new Main());
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.pack();
                f.setLocationRelativeTo(null);
                f.setVisible(true);
            }
        });
    }
}

Answer 1

不是修改JPanel，而是保留它并创建一个新类，JApplet类：

public class YourJApplet extends JApplet{
    public void init(){
        final JPanel panel = new YourPanel();
        this.setContentPane(panel);
    }
}

它就是这样 - 现在你的面板发生了什么，现在是你的JApplet。

在JApplet中使用paintComponent方法

1 个答案: