DelayTimer


1   package net.sf.panoptes.swing.cursor;
2   
3   /**
4    * This class implements a delay timer that will call trigger() 
5    * on the DelayTimerCallback delay milliseconds after 
6    * startTimer() was called, if stopTimer() was not called first.  
7    * The timer will only throw events after startTimer() is called.  
8    * Until then, it does nothing.  It is safe to call stopTimer() 
9    * and startTimer() repeatedly.
10   *
11   * Note that calls to trigger() will happen on the timer thread.
12   *
13   * This class is multiple-thread safe. 
14   */
15  public class DelayTimer extends Thread   {
16    private final DelayTimerCallback callback;
17    private final Object   mutex = new Object  ();
18    private final Object   triggeredMutex = new Object  ();
19    private final long delay;
20    private boolean quit;
21    private boolean triggered;
22    private long waitTime;
23  
24    public DelayTimer(DelayTimerCallback callback, long delay) {
25      this.callback = callback;
26      this.delay = delay;
27      setDaemon(true);
28      start();
29    }
30    /**
31     * Calling this method twice will reset the timer.
32     */
33    public void startTimer() {
34      synchronized (mutex) {
35        waitTime = delay;
36        mutex.notify();
37      }
38    }
39    public void stopTimer() {
40      try {
41        synchronized (mutex) {
42          synchronized (triggeredMutex) {
43            if (triggered) {
44              triggeredMutex.wait();
45            }
46          }
47          waitTime = 0;
48          mutex.notify();
49        }
50      } catch (InterruptedException   ie) {
51        System.err.println("trigger failure");
52        ie.printStackTrace(System.err);
53      }
54    }
55    public void run() {
56      try {
57        while (!quit) {
58          synchronized (mutex) {
59            //we rely on wait(0) being implemented to wait forever here
60            if (waitTime < 0) {
61              triggered = true;
62              waitTime = 0;
63            } else {
64              long saveWaitTime = waitTime;
65              waitTime = -1;
66              mutex.wait(saveWaitTime);
67            }
68          }
69          try {
70            if (triggered) {
71              callback.trigger();
72            }
73          } catch (Exception   e) {
74            System.err.println(
75                "trigger() threw exception, continuing");
76            e.printStackTrace(System.err);
77          } finally {
78            synchronized (triggeredMutex) {
79              triggered = false;
80              triggeredMutex.notify();
81            }
82          }
83        }
84      } catch (InterruptedException   ie) {
85        System.err.println("interrupted in run");
86        ie.printStackTrace(System.err);
87      }
88    }
89    public void quit() {
90      synchronized (mutex) {
91        this.quit = true;
92        mutex.notify();
93      }
94    }
95  }
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