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| 1 | /* | ||
| 2 | * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package java.awt; | ||
| 27 | |||
| 28 | /** | ||
| 29 | * A helper interface to run the nested event loop. | ||
| 30 | * <p> | ||
| 31 | * Objects that implement this interface are created with the | ||
| 32 | * {@link EventQueue#createSecondaryLoop} method. The interface | ||
| 33 | * provides two methods, {@link #enter} and {@link #exit}, | ||
| 34 | * which can be used to start and stop the event loop. | ||
| 35 | * <p> | ||
| 36 | * When the {@link #enter} method is called, the current | ||
| 37 | * thread is blocked until the loop is terminated by the | ||
| 38 | * {@link #exit} method. Also, a new event loop is started | ||
| 39 | * on the event dispatch thread, which may or may not be | ||
| 40 | * the current thread. The loop can be terminated on any | ||
| 41 | * thread by calling its {@link #exit} method. After the | ||
| 42 | * loop is terminated, the {@code SecondaryLoop} object can | ||
| 43 | * be reused to run a new nested event loop. | ||
| 44 | * <p> | ||
| 45 | * A typical use case of applying this interface is AWT | ||
| 46 | * and Swing modal dialogs. When a modal dialog is shown on | ||
| 47 | * the event dispatch thread, it enters a new secondary loop. | ||
| 48 | * Later, when the dialog is hidden or disposed, it exits | ||
| 49 | * the loop, and the thread continues its execution. | ||
| 50 | * <p> | ||
| 51 | * The following example illustrates a simple use case of | ||
| 52 | * secondary loops: | ||
| 53 | * | ||
| 54 | * <pre> | ||
| 55 | * SecondaryLoop loop; | ||
| 56 | * | ||
| 57 | * JButton jButton = new JButton("Button"); | ||
| 58 | * jButton.addActionListener(new ActionListener() { | ||
| 59 | * {@code @Override} | ||
| 60 | * public void actionPerformed(ActionEvent e) { | ||
| 61 | * Toolkit tk = Toolkit.getDefaultToolkit(); | ||
| 62 | * EventQueue eq = tk.getSystemEventQueue(); | ||
| 63 | * loop = eq.createSecondaryLoop(); | ||
| 64 | * | ||
| 65 | * // Spawn a new thread to do the work | ||
| 66 | * Thread worker = new WorkerThread(); | ||
| 67 | * worker.start(); | ||
| 68 | * | ||
| 69 | * // Enter the loop to block the current event | ||
| 70 | * // handler, but leave UI responsive | ||
| 71 | * if (!loop.enter()) { | ||
| 72 | * // Report an error | ||
| 73 | * } | ||
| 74 | * } | ||
| 75 | * }); | ||
| 76 | * | ||
| 77 | * class WorkerThread extends Thread { | ||
| 78 | * {@code @Override} | ||
| 79 | * public void run() { | ||
| 80 | * // Perform calculations | ||
| 81 | * doSomethingUseful(); | ||
| 82 | * | ||
| 83 | * // Exit the loop | ||
| 84 | * loop.exit(); | ||
| 85 | * } | ||
| 86 | * } | ||
| 87 | * </pre> | ||
| 88 | * | ||
| 89 | * @see Dialog#show | ||
| 90 | * @see EventQueue#createSecondaryLoop | ||
| 91 | * @see Toolkit#getSystemEventQueue | ||
| 92 | * | ||
| 93 | * @author Anton Tarasov, Artem Ananiev | ||
| 94 | * | ||
| 95 | * @since 1.7 | ||
| 96 | */ | ||
| 97 | public interface SecondaryLoop { | ||
| 98 | |||
| 99 | /** | ||
| 100 | * Blocks the execution of the current thread and enters a new | ||
| 101 | * secondary event loop on the event dispatch thread. | ||
| 102 | * <p> | ||
| 103 | * This method can be called by any thread including the event | ||
| 104 | * dispatch thread. This thread will be blocked until the {@link | ||
| 105 | * #exit} method is called or the loop is terminated. A new | ||
| 106 | * secondary loop will be created on the event dispatch thread | ||
| 107 | * for dispatching events in either case. | ||
| 108 | * <p> | ||
| 109 | * This method can only start one new event loop at a time per | ||
| 110 | * object. If a secondary event loop has already been started | ||
| 111 | * by this object and is currently still running, this method | ||
| 112 | * returns {@code false} to indicate that it was not successful | ||
| 113 | * in starting a new event loop. Otherwise, this method blocks | ||
| 114 | * the calling thread and later returns {@code true} when the | ||
| 115 | * new event loop is terminated. At such time, this object can | ||
| 116 | * again be used to start another new event loop. | ||
| 117 | * | ||
| 118 | * @return {@code true} after termination of the secondary loop, | ||
| 119 | * if the secondary loop was started by this call, | ||
| 120 | * {@code false} otherwise | ||
| 121 | */ | ||
| 122 | public boolean enter(); | ||
| 123 | |||
| 124 | /** | ||
| 125 | * Unblocks the execution of the thread blocked by the {@link | ||
| 126 | * #enter} method and exits the secondary loop. | ||
| 127 | * <p> | ||
| 128 | * This method resumes the thread that called the {@link #enter} | ||
| 129 | * method and exits the secondary loop that was created when | ||
| 130 | * the {@link #enter} method was invoked. | ||
| 131 | * <p> | ||
| 132 | * Note that if any other secondary loop is started while this | ||
| 133 | * loop is running, the blocked thread will not resume execution | ||
| 134 | * until the nested loop is terminated. | ||
| 135 | * <p> | ||
| 136 | * If this secondary loop has not been started with the {@link | ||
| 137 | * #enter} method, or this secondary loop has already finished | ||
| 138 | * with the {@link #exit} method, this method returns {@code | ||
| 139 | * false}, otherwise {@code true} is returned. | ||
| 140 | * | ||
| 141 | * @return {@code true} if this loop was previously started and | ||
| 142 | * has not yet been finished with the {@link #exit} method, | ||
| 143 | * {@code false} otherwise | ||
| 144 | */ | ||
| 145 | public boolean exit(); | ||
| 146 | |||
| 147 | } | ||