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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