[3952] | 1 | package nu.fw.jeti.util; |
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| 2 | |
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| 3 | import javax.swing.SwingUtilities; |
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| 4 | |
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| 5 | /** |
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| 6 | * This is the 3rd version of SwingWorker (also known as |
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| 7 | * SwingWorker 3), an abstract class that you subclass to |
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| 8 | * perform GUI-related work in a dedicated thread. For |
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| 9 | * instructions on and examples of using this class, see: |
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| 10 | * |
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| 11 | * http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html |
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| 12 | * |
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| 13 | * Note that the API changed slightly in the 3rd version: |
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| 14 | * You must now invoke start() on the SwingWorker after |
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| 15 | * creating it. |
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| 16 | */ |
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| 17 | public abstract class SwingWorker { |
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| 18 | private Object value; // see getValue(), setValue() |
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| 19 | |
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| 20 | /** |
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| 21 | * Class to maintain reference to current worker thread |
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| 22 | * under separate synchronization control. |
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| 23 | */ |
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| 24 | private static class ThreadVar { |
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| 25 | private Thread thread; |
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| 26 | ThreadVar(Thread t) { thread = t; } |
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| 27 | synchronized Thread get() { return thread; } |
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| 28 | synchronized void clear() { thread = null; } |
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| 29 | } |
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| 30 | |
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| 31 | private ThreadVar threadVar; |
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| 32 | |
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| 33 | /** |
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| 34 | * Get the value produced by the worker thread, or null if it |
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| 35 | * hasn't been constructed yet. |
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| 36 | */ |
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| 37 | protected synchronized Object getValue() { |
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| 38 | return value; |
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| 39 | } |
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| 40 | |
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| 41 | /** |
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| 42 | * Set the value produced by worker thread |
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| 43 | */ |
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| 44 | private synchronized void setValue(Object x) { |
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| 45 | value = x; |
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| 46 | } |
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| 47 | |
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| 48 | /** |
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| 49 | * Compute the value to be returned by the <code>get</code> method. |
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| 50 | */ |
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| 51 | public abstract Object construct(); |
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| 52 | |
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| 53 | /** |
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| 54 | * Called on the event dispatching thread (not on the worker thread) |
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| 55 | * after the <code>construct</code> method has returned. |
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| 56 | */ |
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| 57 | public void finished() { |
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| 58 | } |
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| 59 | |
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| 60 | /** |
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| 61 | * A new method that interrupts the worker thread. Call this method |
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| 62 | * to force the worker to stop what it's doing. |
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| 63 | */ |
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| 64 | public void interrupt() { |
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| 65 | Thread t = threadVar.get(); |
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| 66 | if (t != null) { |
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| 67 | t.interrupt(); |
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| 68 | } |
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| 69 | threadVar.clear(); |
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| 70 | } |
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| 71 | |
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| 72 | /** |
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| 73 | * Return the value created by the <code>construct</code> method. |
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| 74 | * Returns null if either the constructing thread or the current |
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| 75 | * thread was interrupted before a value was produced. |
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| 76 | * |
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| 77 | * @return the value created by the <code>construct</code> method |
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| 78 | */ |
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| 79 | public Object get() { |
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| 80 | while (true) { |
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| 81 | Thread t = threadVar.get(); |
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| 82 | if (t == null) { |
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| 83 | return getValue(); |
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| 84 | } |
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| 85 | try { |
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| 86 | t.join(); |
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| 87 | } |
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| 88 | catch (InterruptedException e) { |
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| 89 | Thread.currentThread().interrupt(); // propagate |
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| 90 | return null; |
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| 91 | } |
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| 92 | } |
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| 93 | } |
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| 94 | |
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| 95 | |
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| 96 | /** |
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| 97 | * Start a thread that will call the <code>construct</code> method |
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| 98 | * and then exit. |
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| 99 | */ |
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| 100 | public SwingWorker() { |
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| 101 | final Runnable doFinished = new Runnable() { |
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| 102 | public void run() { finished(); } |
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| 103 | }; |
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| 104 | |
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| 105 | Runnable doConstruct = new Runnable() { |
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| 106 | public void run() { |
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| 107 | try { |
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| 108 | setValue(construct()); |
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| 109 | } |
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| 110 | finally { |
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| 111 | threadVar.clear(); |
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| 112 | } |
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| 113 | |
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| 114 | SwingUtilities.invokeLater(doFinished); |
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| 115 | } |
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| 116 | }; |
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| 117 | |
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| 118 | Thread t = new Thread(doConstruct); |
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| 119 | threadVar = new ThreadVar(t); |
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| 120 | } |
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| 121 | |
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| 122 | /** |
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| 123 | * Start the worker thread. |
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| 124 | */ |
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| 125 | public void start() { |
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| 126 | Thread t = threadVar.get(); |
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| 127 | if (t != null) { |
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| 128 | t.start(); |
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| 129 | } |
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| 130 | } |
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| 131 | } |
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| 132 | |
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| 133 | /* |
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| 134 | * Overrides for emacs |
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| 135 | * Local variables: |
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| 136 | * tab-width: 4 |
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| 137 | * End: |
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| 138 | */ |
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