求助实现倒计时器的一个功能。

Question

thread

Answer 1

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;import java.time.*;public class CountDownTimerExample {
    public static void main(String[] args) {
        java.awt.EventQueue.invokeLater(new Runnable(){
                @Override public void run(){
                    final JFrame frame = new JFrame("CountDownTimerExample");                    final JLabel message = new JLabel("");
                    frame.add(message);
                    final JButton start = new JButton("Start");                    final Timer timer = new Timer(100, new ActionListener(){
                        Duration d = Duration.ofSeconds(5);
                        @Override public void actionPerformed(ActionEvent e){
                            if(d.isNegative()) return;
                            message.setText(d.toString().substring(2));
                            d = d.minusMillis(100);
                        }
                    });
                    start.addActionListener(new ActionListener(){
                        @Override public void actionPerformed(ActionEvent e){
                            timer.start();
                        }
                    });
                    frame.add(start, BorderLayout.PAGE_END);
                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    frame.setPreferredSize(new Dimension(300,200));
                    frame.pack();
                    frame.setVisible(true);                }
            });
    }
}
Java8编译运行

Answer 2

jdk6 编译， swing界面，开始，暂停，继续按钮。
写的不好，仅供参考import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingConstants;
import javax.swing.SwingUtilities;public class CountDownDemo extends JFrame {
    private final String COUNT = "10.0";
    private final String START = "start";
    private final String PAUSE = "pause";
    private final String RESUME = "resume";
    
    private JLabel jlblCountDown;
    private JButton jbtnStart;
    private JButton jbtnPause;
    
    private ActionListener listener = new ActionListener() {
        boolean available = true; // 倒计时是否工作
        boolean isRunning = false; // 线程是否在运行
        Thread t = null;
        @Override
        public void actionPerformed(ActionEvent e) {
            Object source = e.getSource();
            if(t == null){
                t = new Thread(new Runnable() {
                    
                    @Override
                    public void run() {
                        float i = Float.parseFloat(COUNT);
                        while(i > 0){
                            if(available){
                                try {
                                    Thread.sleep(100);
                                } catch (InterruptedException e) {
                                    e.printStackTrace();
                                }
                                i -= 0.1f;
                                jlblCountDown.setText(String.format("%.1f", i<0?0:i));
                            }
                        }
                        isRunning = false;
                        t = null;
                    }
                });
            }
            if(source == jbtnStart){
                if(!isRunning){
                    isRunning = true;
                    t.start();
                }
            }
            else if(source == jbtnPause){
                if(PAUSE.equals(jbtnPause.getText())){
                    jbtnPause.setText(RESUME);
                    available = false;
                }
                else{
                    available = true;
                    jbtnPause.setText(PAUSE);
                }
            }
        }
    };
    
    private void initUI(){
        jlblCountDown = new JLabel(COUNT, SwingConstants.CENTER);
        jbtnStart = new JButton(START);
        jbtnPause = new JButton(PAUSE);
        
        JPanel panel = new JPanel();
        panel.add(jbtnStart);
        panel.add(jbtnPause);
        add(jlblCountDown, BorderLayout.CENTER);
        add(panel, BorderLayout.SOUTH);
        
        jbtnStart.addActionListener(listener);
        jbtnPause.addActionListener(listener);
    }
    
    public CountDownDemo(){
        initUI();
        setSize(300, 300);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    
    
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            
            @Override
            public void run() {
                CountDownDemo demo = new CountDownDemo();
                demo.setVisible(true);
            }
        });
    }
}