Swing and Thread: repaint

  

import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Font;
import java.lang.reflect.InvocationTargetException;
import java.text.DecimalFormat;

import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingConstants;
import javax.swing.SwingUtilities;

public class DigitalTimer extends JLabel {
  private volatile String timeText;

  private Thread internalThread;

  private volatile boolean noStopRequested;

  public DigitalTimer() {
    setBorder(BorderFactory.createLineBorder(Color.black));
    setHorizontalAlignment(SwingConstants.RIGHT);
    setFont(new Font("SansSerif", Font.BOLD, 16));
    setText("00000.0"); // use to size component
    setMinimumSize(getPreferredSize());
    setPreferredSize(getPreferredSize());
    setSize(getPreferredSize());

    timeText = "0.0";
    setText(timeText);

    noStopRequested = true;
    Runnable r = new Runnable() {
      public void run() {
        try {
          runWork();
        } catch (Exception x) {
          x.printStackTrace();
        }
      }
    };

    internalThread = new Thread(r, "DigitalTimer");
    internalThread.start();
  }

  private void runWork() {
    long startTime = System.currentTimeMillis();
    int tenths = 0;
    long normalSleepTime = 100;
    long nextSleepTime = 100;
    DecimalFormat fmt = new DecimalFormat("0.0");

    Runnable updateText = new Runnable() {
      public void run() {
        setText(timeText);
      }
    };

    while (noStopRequested) {
      try {
        Thread.sleep(nextSleepTime);

        tenths++;
        long currTime = System.currentTimeMillis();
        long elapsedTime = currTime - startTime;

        nextSleepTime = normalSleepTime
            + ((tenths * 100) - elapsedTime);

        if (nextSleepTime < 0) {
          nextSleepTime = 0;
        }

        timeText = fmt.format(elapsedTime / 1000.0);
        SwingUtilities.invokeAndWait(updateText);
      } catch (InterruptedException ix) {
        // stop running
        return;
      } catch (InvocationTargetException x) {
        x.printStackTrace();
      }
    }
  }

  public void stopRequest() {
    noStopRequested = false;
    internalThread.interrupt();
  }

  public boolean isAlive() {
    return internalThread.isAlive();
  }

  public static void main(String[] args) {

    JFrame f = new JFrame();
    f.getContentPane().setLayout(new FlowLayout());
    f.getContentPane().add(new DigitalTimer());
    f.setSize(250, 100);
    f.setVisible(true);
  }
}

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Swing and Thread: repaint : Swing Thread « Threads « Java

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