java - 在Java中画椭圆

Question

我有一个java程序，它在屏幕上显示一个椭圆并通过使用箭头键改变它的方向。我经常使用 while 循环在椭圆上调用 repaint()。

椭圆移动，但问题是它在其路径上留下了椭圆的痕迹。我该如何制作才能删除旧的省略号，然后重新绘制新的省略号？

代码:

public void run(){
        while (animator != null) 
        {
            setBackground(Color.GREEN);
            repaint();
                            // The direction works and the rest works fine.
            player1.move(player1, player1.direction);
            try  
            {  
                Thread.sleep(100);  
            }  
            catch (InterruptedException e)  
            {  
                break;  
            }  
        }
}

// The paintComponent of my player1 is fine.
public void paint(Graphics g){
        Graphics2D g2 = (Graphics2D)g;
        player1.paintComponent(g2, player1);
}

Answer 1

问题可能是您的 paintComponent(Graphics) 重写方法没有调用 super.paintComponent(g)，它会清除 Canvas 等:

// Bad:
@Override
public void paintComponent(Graphics g) {
    // paint the ellipse, etc.
}

// Good:
@Override
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    // paint the ellipse, etc.
}