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30 <META NAME="Author" Content="Eric Armstrong">
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32 <TITLE>swing package</TITLE>
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36
37 <P>Provides a set of "lightweight"
38 (all-Java language) components that,
39 to the maximum degree possible, work the same on all platforms.
40 For a programmer's guide to using these components, see
41 <a href="http://java.sun.com/docs/books/tutorial/uiswing/index.html"
42 target="_top">Creating
43 a GUI with JFC/Swing</a>, a trail in <em>The Java Tutorial</em>.
44 For other resources, see
45 <a href="#related">Related Documentation</a>.
46
47 <H2><a name="threading">Swing's Threading Policy</a></h2>
48
49 In general Swing is not thread safe. All Swing components and related
50 classes, unless otherwise documented, must be accessed on the event
51 dispatching thread.
52 <p>
53 Typical Swing applications do processing in response to an event
54 generated from a user gesture. For example, clicking on a {@code
55 JButton} notifies all {@code ActionListeners} added to the {@code
56 JButton}. As all events generated from a user gesture are
57 dispatched on the event dispatching thread, most developers are not
58 impacted by the restriction.
59 <p>
60 Where the impact lies, however, is in constructing and showing a
61 Swing application. Calls to an application's {@code main} method,
62 or methods in {@code Applet}, are not invoked on the event
63 dispatching thread. As such, care must be taken to transfer control
64 to the event dispatching thread when constructing and showing an
65 application or applet. The preferred way to transfer control and begin
66 working with Swing is to use {@code invokeLater}. The {@code
67 invokeLater} method schedules a {@code Runnable} to be processed on
68 the event dispatching thread. The following two examples work equally
69 well for transferring control and starting up a Swing application:
70 <pre>
71 import javax.swing.SwingUtilities;
72
73 public class MyApp implements Runnable {
74 public void run() {
75 // Invoked on the event dispatching thread.
76 // Construct and show GUI.
77 }
78
79 public static void main(String[] args) {
80 SwingUtilities.invokeLater(new MyApp());
81 }
82 }
83 </pre>
84 Or:
85 <pre>
86 import javax.swing.SwingUtilities;
87
88 public class MyApp {
89 MyApp(String[] args) {
90 // Invoked on the event dispatching thread.
91 // Do any initialization here.
92 }
93
94 public void show() {
95 // Show the UI.
96 }
97
98 public static void main(final String[] args) {
99 // Schedule a job for the event-dispatching thread:
100 // creating and showing this application's GUI.
101 SwingUtilities.invokeLater(new Runnable() {
102 public void run() {
103 new MyApp(args).show();
104 }
105 });
106 }
107 }
108 </pre>
109 This restriction also applies to models attached to Swing components.
110 For example, if a {@code TableModel} is attached to a {@code
111 JTable}, the {@code TableModel} should only be modified on the
112 event dispatching thread. If you modify the model on a separate
113 thread you run the risk of exceptions and possible display
114 corruption.
115 <p>
116 As all events are delivered on the event dispatching thread, care must
117 be taken in event processing. In particular, a long running task, such
118 as network io or computational intensive processing, executed on the
119 event dispatching thread blocks the event dispatching thread from
120 dispatching any other events. While the event dispatching thread is
121 blocked the application is completely unresponsive to user
122 input. Refer to {@link javax.swing.SwingWorker} for the preferred way to do such
123 processing when working with Swing.
124 <p>
125 More information on this topic can be found in the
126 <a href="http://download.oracle.com/javase/tutorial/uiswing/">Swing tutorial</a>,
127 in particular the section on
128 <a href="http://download.oracle.com/javase/tutorial/uiswing/concurrency/index.html">Concurrency in Swing</a>.
129
130
131 <H2>
132 <a name="related">Related Documentation</a>
133 </H2>
134 <P>For overviews, tutorials, examples, guides, and other documentation, please see:
135
136 <UL>
137 <LI><A HREF="http://java.sun.com/products/jfc/tsc/"
138 target="_top">The Swing Connection</A>
139 <LI><A HREF="http://java.sun.com/docs/books/tutorial/"
140 target="_top">The Java Tutorial</A>
141 <LI><A HREF="http://java.sun.com/developer/onlineTraining/"
142 target="_top">Online Training</A> at the Java Developer Connection<font size=-2><sup>SM</sup></font>
143 <LI><A HREF="http://java.sun.com/products/jfc/"
144 target="_top">Java Foundation Classes (JFC)</A> home page
145 </UL>
146
147 @serial exclude
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