再次更新JFrame

Question

下面显示的以下代码会将3个JLabel添加到JFrame中，然后删除3个JLabel。2秒后，它将重新绘制3个JLabel。

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

@SuppressWarnings("serial")
public class RepaintFrameTest extends JFrame {
    private JPanel panel = new JPanel();
    private JLabel labelOne = new JLabel("label1");
    private JLabel labelTwo = new JLabel("label2");
    private JLabel labelThree = new JLabel("label3");
    public RepaintFrameTest() { 
        panel.add(labelOne);
        panel.add(labelTwo);
        panel.add(labelThree);
        add(panel);
        pack();
        setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        setSize(1024,768);
        setLocationRelativeTo(null);
        setVisible(true);
    }

    public static void main(String args[]) {
        RepaintFrameTest frameOne = new RepaintFrameTest();
        frameOne.getContentPane().removeAll();   
        frameOne.getContentPane().validate();
        frameOne.getContentPane().repaint();
        new Thread(new RepaintThread()).start();
    }
}

class RepaintThread implements Runnable {
    @Override
    public void run() {
        try   {              
            Thread.sleep(2000);            
        }catch (InterruptedException interruptedException)  {                           
            System.out.println( "Thread is interrupted when it is sleeping" +interruptedException);             
        } 
        RepaintFrameTest frameTwo = new RepaintFrameTest();
        frameTwo.getContentPane().validate();
        frameTwo.getContentPane().repaint();
    }
}

我面临的一个小问题是，它正在重新绘制到新的frame（frameTwo）而不是旧的frame（frameOne）。

如何使它重新绘制现有框架而不是重新绘制到新框架？

Answer 1

1. Simpy使用CardLayout来交换视图。
2. 请使用Swing计时器，而不要使用当前的后台线程，因为您当前的代码对Swing线程而言并不安全，并且存在发生危险的不可预测的线程异常的风险。
3. 我会给主JPanel CardLayout，然后添加一个JLabel来保存带有合适的String常量的JPanel。
4. 然后，我将使用JPanel添加到主CardLayout中，将一个空的JLabel添加到add方法中的另一个String常量中。即add(new JLabel(), BLANK_COMPONENT);
5. 然后，在Swing Timer中，只需调用next()CardLayout对象，传入使用CardLayout的主要组件：cardLayout.next(myMainJPanel);

例如，

import java.awt.CardLayout;
import java.awt.Dimension;
import java.awt.event.*;

import javax.swing.*;

public class RepaintTest extends JPanel {
   private static final int PREF_W = 400;
   private static final int PREF_H = PREF_W;
   private static final int LABEL_COUNT = 3;
   private static final String LABEL_PANEL = "label panel";
   private static final Object BLANK_COMPONENT = "blank component";
   private static final int TIMER_DELAY = 2000;
   private CardLayout cardLayout = new CardLayout();

   public RepaintTest() {
      JPanel labelPanel = new JPanel();
      for (int i = 0; i < LABEL_COUNT; i++) {
         labelPanel.add(new JLabel("Label " + (i + 1)));
      }

      setLayout(cardLayout);
      add(labelPanel, LABEL_PANEL);
      add(new JLabel(), BLANK_COMPONENT);

      new Timer(TIMER_DELAY, new TimerListener()).start();

   }

   @Override
   public Dimension getPreferredSize() {
      return new Dimension(PREF_W, PREF_H);
   }

   private class TimerListener implements ActionListener {
      @Override
      public void actionPerformed(ActionEvent e) {
         cardLayout.next(RepaintTest.this);
      }
   }

   private static void createAndShowGui() {
      RepaintTest mainPanel = new RepaintTest();

      JFrame frame = new JFrame("RepaintTest");
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}