如何每次使用带有延迟的while循环更新jLabel [英] how to update a jLabel every time with a while loop with a delay

问题描述

   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 上显示最终数字，但它不会增量更新数字.任何帮助

It will eventually show the final number on the jLabel but it does not incrementally update the number. any help

推荐答案

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 javax.swing.Timer.这将在后台线程中延迟，然后在 EDT 中发布要执行的操作.

Swing is single-threaded. Therefore, long-running tasks should never take place in the EDT. This includes sleeping. Instead, use a javax.swing.Timer. This will delay in a background thread, and then post an action to be executed in the EDT.

另见:

• 如何使用 Swing 计时器

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 模仿了一个计数器，每秒从 0 开始计数(即更新 JLabel 实例)直到应用程序终止.

This SSCCE imitates a counter that will count up from 0 every second (i.e. update the JLabel instance) until the application is terminated.

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