線程之間的多線程和傳輸變量

Question

我想在java中製作一個秒錶。

我的第一個問題是，在第46行，我應該在一個新的線程啓動timerMethod，但我不知道如何做到這一點。

第二個問題是行44,45和53有錯誤，說「本地變量isTiming在封閉範圍內定義必須是最終的或有效的最終」。

代碼：

import java.awt.Container; 
import java.awt.Dimension; 
import java.awt.Font; 
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; 

public class Stopwatch { 
    public static void main(String[] args) { 
     windowMethod(); 
    } 
    public static void windowMethod() { 
     //create frame 
     JFrame frame = new JFrame(); 
     frame.setSize(900, 600); 
     frame.setResizable(false); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     frame.setVisible(true); 
     //create panel 
     JPanel panel = new JPanel(); 
     frame.add(panel); 
     panel.setLayout(null); 
     //create time label 
     JLabel timeLabel = new JLabel("00:00:00"); 
     panel.add(timeLabel); 
     timeLabel.setFont(new Font("Tahoma",Font.PLAIN, 32)); 
     Dimension timeLabelSize = timeLabel.getPreferredSize(); 
     int timeLabelx = (450-(timeLabelSize.width/2)); 
     timeLabel.setBounds(timeLabelx, 50, timeLabelSize.width, timeLabelSize.height); 
     //create start/stop button 
     JButton startStopButton = new JButton("Start Timer"); 
     panel.add(startStopButton); 
     startStopButton.setFont(new Font("Tahoma",Font.PLAIN, 32)); 
     Dimension startStopButtonSize = startStopButton.getPreferredSize(); 
     int startStopButtonx = (450-(startStopButtonSize.width/2)); 
     startStopButton.setBounds(startStopButtonx, 150, startStopButtonSize.width, startStopButtonSize.height); 
     boolean isTiming = false; 
     startStopButton.addActionListener(new ActionListener() { 
      public void actionPerformed(ActionEvent e) { 
       if (isTiming = false) { //This runs if the button is clicked to start the timer 
        isTiming = true; 
        timerMethod(isTiming); //runs the timerMethod in a new thread? 
        startStopButton.setText("Stop Timer"); 
        Dimension startStopButtonSize = startStopButton.getPreferredSize(); 
        int startStopButtonx = (450-(startStopButtonSize.width/2)); 
        startStopButton.setBounds(startStopButtonx, 150, startStopButtonSize.width, startStopButtonSize.height); 
       } 
       else { //This runs if the button is clicked to stop the timer 
        isTiming = false; 
        startStopButton.setText("Start Timer"); 
        Dimension startStopButtonSize = startStopButton.getPreferredSize(); 
        int startStopButtonx = (450-(startStopButtonSize.width/2)); 
        startStopButton.setBounds(startStopButtonx, 150, startStopButtonSize.width, startStopButtonSize.height); 
       } 
      } 
     }); 
    } 
    public static String timerMethod(boolean isTiming) { 
     int milliseconds = 0; 
     int seconds = 0; 
     int minutes = 0; 
     while(isTiming = true) { 
      milliseconds++; 
      if (milliseconds > 999) { 
       milliseconds = 0; 
       seconds++; 
       if (seconds > 59) { 
        seconds = 0; 
        minutes++; 
       } 
      } 
     } 
     String outputTime = (minutes + ":" + seconds + ":" + milliseconds); 
     return outputTime; 
    } 
} 

Answer 1

的timerMethod實際上應該是一個類繼承Thread類，它應該從另一個線程停止的方式的run()方法。

我可以建議您仔細閱讀Oracle網站https://docs.oracle.com/javase/tutorial/essential/concurrency/index.html上的併發課程嗎？