Windows重叠时会擦除JFrame的内容

Question

我使用JFrame创建并显示一个窗口,并将其设置为非常基本的属性.

public FrameVertices( String sTitle, Graph mMap, int iMul ) {
    super( sTitle );

    setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
    setSize ( 300, 300 );
    setLocation ( 600, 300 );
    setVisible ( true);

    this.iMul = iMul;
    this.gGraph = mMap;
}

然后我使用paint()方法在窗口内绘制一些东西.

问题是,当其他一些窗户覆盖我JFrame然后揭开它时,它的内容JFrame不会被重新绘制 - 除非我调整大小或最小/最大JFrame.

我错过了什么吗？

Answer 1

直接绘画是不好的做法JFrame.更好的方法是覆盖paintComponent()a JPanel 并添加JPanel 到JFrame:

Test.java:

public class Test extends JFrame {

    public static void main(String[] args) {

       SwingUtilities.invokeLater(new Runnable() {
          public void run() {
           new Test().createUI();
          }
       });

    }

  void createUI() {

             setSize(500,500);
             getContentPane().add(new MyPanel());
             setVisible(true);      
       }
}

MyPanel.java:

class MyPanel extends JPanel {

    @override
    public void paintComponent(Graphics g) {
      super.paintComponent(g);
      //paint what you want here
      g.drawString("Hello world",250,250);
    }
}

但是,如果必须,我建议添加一个Window FocusListener并repaint()在JFrame实例引起关注时调用该实例:http://docs.oracle.com/javase/tutorial/uiswing/events/windowlistener.html

通过该方法windowGainedFocus(WindowEvent e)或windowStateChanged(WindowEvent e)或windowActivated(WindowEvent e)主叫repaint()在这些方法1然后将调用paint()方法.