java - 使用 Jlabel 的 javax 计时器没有运气

Question

我在使用计时器更新 JLabel 时仍然遇到问题。我似乎无法弄清楚我错过了什么。全局第二个变量保持为零，所以我猜测计时器正在工作但没有更新 GUI 窗口？

 import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

class Globals 
{
    public static int seconds = 0;
}

class main
{
    public static void main(String Args[])
    {

        //text timeline = new text();
        JFrame testing = new JFrame();
        frame textdes = new frame();
        testing.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        testing.setSize(1000,1000);
        testing.setVisible(true);

        Countdown timer = new Countdown();
        Timer countdown = new Timer(5000, timer);
        countdown.start();

        JLabel countdowntext = new JLabel();
        countdowntext.setText("Now its :" + Globals.seconds);
        testing.add(countdowntext);     
        testing.add(textdes);

    }
}

class frame extends JFrame
{
    class Countdown implements ActionListener 
    {
        public void actionPerformed(ActionEvent e)
        {
            Globals.seconds++;
        }
    }
}

Answer 1

您仅在程序中设置标签文本一次。然后计时器更改变量的值，但不对标签执行任何操作。应该这样做:

Globals.seconds++;
countdowntext.setText("Now its :" + Globals.seconds);

这是一个完整的示例:

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

class Globals {
    public static int seconds = 0;
}

class Main {
    public static void main(String Args[]) {

        //text timeline = new text();
        JFrame testing = new JFrame();
        testing.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        testing.setSize(1000,1000);
        testing.setVisible(true);

        JLabel countDownLabel = new JLabel();
        countDownLabel.setText("Now it's : " + Globals.seconds);
        testing.add(countDownLabel);

        CountDown countdown = new CountDown(countDownLabel);
        Timer timer = new Timer(5000, countDown);
        timer.start();
    }
}

class CountDown implements ActionListener {
    private JLabel countDownLabel;

    public CountDown(JLabel countDownLabel) {
        this.countDownLabel = countDownLabel;
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        Globals.seconds++;
        this.countDownLabel.setText("Now it's : " + Globals.seconds);
    }
}