Java等待swing.timer任務完成，然后再執行下一個任務

Question

因此標題確實說明了一切。 在執行方法中的下一個命令之前，我需要線程等待計時器完成。

碼：

import javax.swing.Timer;

public class doesntMatter
{
    Timer timer;
    ActionListener timerTask;

    public doesntMatter
    {
         timerTask = new ActionListener()
         {
              @Override
              public void actionPerformed(ActionEvent e)
              {
                  //taskSomethingIdk
              }
         }
    }

    private void whatever
    {
        timer = new Timer(1000, timerTask);
        timer.setInitialDelay(0);
        timer.start();

        // here i need to wait for the timer to finish

        if(timerhasfrigginfinished)
             continueOrSomethingIdk
    }

}

Answer 1

假設您的計時器重復執行，請在Timer的ActionListener中進行檢查，以查看其是否正在運行上一次重復，如果是， 則在其中調用continueOrSomethingIdk()方法。

否則，您將必須建立自己的通知機制，即回叫，以便計時器可以通知所有偵聽器它已完成運行。

例如：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

@SuppressWarnings("serial")
public class WhenTimerDone extends JPanel {
    private static final Color[] COLORS = { 
            Color.RED, Color.ORANGE, 
            Color.YELLOW, Color.GREEN,
            Color.BLUE, Color.CYAN };
    private static final String START = "Start";
    private static final String DONE = "Done";
    private static final int PREF_W = 400;
    private static final int PREF_H = PREF_W;
    public static final int TIMER_DELAY = 1000;
    private JLabel statusLabel = new JLabel(START);
    private StartAction startAction = new StartAction("Start!");

    public WhenTimerDone() {
        add(statusLabel);
        add(new JButton(startAction));
    }

    @Override
    public Dimension getPreferredSize() {
        if (isPreferredSizeSet()) {
            return super.getPreferredSize();
        }
        return new Dimension(PREF_W, PREF_H);
    }

    // this is the method called by the Timer's ActionListener when it is done
    public void done() {
        // reset all to baseline state
        statusLabel.setText(DONE);
        startAction.setEnabled(true);
        setBackground(null);
    }

    // ActionListener for the start button
    private class StartAction extends AbstractAction {

        public StartAction(String name) {
            super(name);
            int mnemonic = (int) name.charAt(0);
            putValue(MNEMONIC_KEY, mnemonic);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            // disables itself
            setEnabled(false);
            statusLabel.setText(START); // updates the status label

            // create and start a timer
            Timer timer = new Timer(TIMER_DELAY, new TimerListener());
            timer.setInitialDelay(0);
            timer.start();    
        }
    }

    // action listener for the timer
    private class TimerListener implements ActionListener {
        private int colorsIndex = 0;

        @Override
        public void actionPerformed(ActionEvent e) {
            // simply loops through a colors array, changing background color
            if (colorsIndex < COLORS.length) {
                setBackground(COLORS[colorsIndex]);
                colorsIndex++;
            } else {
                // when all colors shown -- stop the timer
                ((Timer) e.getSource()).stop();

                // and call the done method -- ******* here's the key!
                done();  // called when Timer is done!
            }
        }
    }

    private static void createAndShowGui() {
        WhenTimerDone mainPanel = new WhenTimerDone();

        JFrame frame = new JFrame("WhenTimerDone");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGui());
    }
}

Answer 2

這里的關鍵字是notify / wait您的計時器線程應通知另一個應等待的線程，如下所示：

import javax.swing.Timer;

public class doesntMatter
{
Timer timer;
ActionListener timerTask;

public doesntMatter
{
     timerTask = new ActionListener()
     {
          @Override
          public void actionPerformed(ActionEvent e)
          {
              synchronized(timer){
                  //taskSomethingIdk
                  //you would have to rig something so we can access a common object as the monitor/lock object
                  timer.notify()
              }
          }
     }
}

private void whatever
{
    timer = new Timer(1000, timerTask);
    timer.setInitialDelay(0);
    timer.start();
    //Need to obtain a lock on the "monitor" object
    //Lock will be released while it is waiting
    synchronized(timer){
        timer.wait()
        //do whatever
    }
}

}

這將使“主”線程等待，直到計時器線程調用notify方法，然后喚醒其中一個等待線程。

我也不認為“ ActionListener”擴展了“ TimerTask”。 因此，由於向您提供了一個ActionListener給Timer，該代碼示例可能無法編譯，該Timer希望使用TimerTask作為輸入。 也許我以某種方式不理解您的代碼應該做什么。

請參閱如何在Java中使用等待和通知？ 欲獲得更多信息。