显示新旧数字的Jlabel

Question

public static void main(String[] args) {
    JFrame frame = new JFrame("FrameDemo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
    //frame.setSize(500, 500);
    frame.setUndecorated(true);
    frame.getContentPane().setBackground(Color.GREEN);
    final long tStart = System.currentTimeMillis();
    long tNow = 0;
    System.out.println(tStart);
    while (1 != 0) {
        add_time(tNow, frame);
    }
}

public static void add_time(long tStart, JFrame frame) {
    long tNow = System.currentTimeMillis();

    if ((tNow - tStart) % 10000 >= 5000) {
        frame.setVisible(true);
        //System.out.println((tNow - tStart) % 10000);
        JLabel label = new JLabel("Test", JLabel.CENTER);
        label.setText(String.valueOf((tNow - tStart) % 10000));
        label.setFont(new Font("Serif", Font.BOLD, 240));
        label.setSize(500, 500);
        frame.add(label);
        //label.setText("");
    } else frame.setVisible(false);

}

}

Answer 1

frame.add(label);

不要不停地向框架添加组件。去掉那句话。

相反，您需要更新框架上的现有标签：

因此，您需要进行几项更改：

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

public class TimerTime extends JPanel implements ActionListener
{
    private JLabel timeLabel;
    private int count = 0;

    public TimerTime()
    {
        timeLabel = new JLabel( new Date().toString() );
        add( timeLabel );

        Timer timer = new Timer(1000, this);
        timer.setInitialDelay(1);
        timer.start();
    }

    @Override
    public void actionPerformed(ActionEvent e)
    {
        //System.out.println(e.getSource());
        timeLabel.setText( new Date().toString() );
//      timeLabel.setText( String.valueOf(System.currentTimeMillis() ) );
        count++;

        if (count == 10)
        {
            Timer timer = (Timer)e.getSource();
            timer.stop();
        }
    }

    private static void createAndShowUI()
    {
        JFrame frame = new JFrame("TimerTime");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add( new TimerTime() );
        frame.setLocationByPlatform( true );
        frame.pack();
        frame.setVisible( true );
    }

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