运行这个application,窗体中会莫名其妙的出现无法点击的按键.

Question

class timerTestPanel extends JPanel implements ActionListener
{
    public timerTestPanel()
    {
        int barLength=0;
    }    public void actionPerformed(ActionEvent evt)
    {
        repaint();
    }    public void paintComponent(Graphics g)
    {
super.paintComponent(g);//Add this line
        barLength++;
        g.fillRect(0,0,barLength,barWidth);
    }    private final int barWidth=20;    //??????.??????.
    private int barLength;    //??????,?????????.??????.}

Answer 1

super.paintComponent(g);//Add this line
swing 的paintComponent重载都要先调用super.paintComponent(g);

Answer 2

to masterz:
 谢谢,确实就缺super.paintComponent(g);语句导致产生了这个怪问题.