java如何使用带有延迟的while循环每次更新jLabel

Question

   private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
  int count = jSlider1.getValue(); 
  int delay = jSlider2.getValue();
    int valueOfSlider = jSlider2.getValue();
     int valueOfSlider2 = jSlider1.getValue();

while (count > 0) 
{ 
    count--;
    String count2 = ""+count; 
  jLabel3.setText(count2);
try {Thread.sleep(delay); }
catch (InterruptedException ie) { }

 }

它最终会在jLabel上显示最终的数字，但不会增量更新数字。需要帮忙吗

Answer 1

你的问题是，你在ActionPerformed回调中做一些耗时的事情，该回调在事件线程中执行。在回调中，您应该快速执行某个操作并返回，即使“某个”正在生成线程。当您占用事件线程时，GUI无法更新，它只会在回调返回后更新

Answer 2

Swing是单线程的。因此，长时间运行的任务不应该在EDT中进行。这包括睡觉。相反，使用^{}。这将在后台线程中延迟，然后在EDT中发布要执行的操作

另见：

• How to Use Swing Timers

---

import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;

public final class JLabelUpdateDemo {

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

    private static void createAndShowGUI(){
        final JFrame frame = new JFrame("Update JLabel Demo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(new FlowLayout());
        frame.getContentPane().add(JTimerLabel.getInstance());
        frame.setSize(new Dimension(275, 75)); // used for demonstration purposes
        //frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);

        Timer t = new Timer(1000, new ActionListener(){
            @Override
            public void actionPerformed(ActionEvent e) {
                int val = Integer.valueOf(JTimerLabel.getInstance().getText());
                JTimerLabel.getInstance().setText(String.valueOf(++val));
            }
        });
        t.start();
    }

    private static final class JTimerLabel extends JLabel{
        private static JTimerLabel INSTANCE;

        private JTimerLabel(){
            super(String.valueOf(0));
            setFont(new Font("Courier New", Font.BOLD,  18));
        }

        public static final JTimerLabel getInstance(){
            if(INSTANCE == null){
                INSTANCE = new JTimerLabel();
            }

            return INSTANCE;
        }
    }
}

这个SSCCE模拟每秒从0开始计数的计数器（即更新JLabel实例），直到应用程序终止