1 /*******************************************************************************

     2  * Copyright (c) 2009, 2010 Nokia Corporation and/or its subsidiary(-ies).

     3  * All rights reserved. This program and the accompanying materials 

     4  * are made available under the terms of the Eclipse Public License v1.0

     5  * which accompanies this distribution, and is available at

     6  * http://www.eclipse.org/legal/epl-v10.html

     7  * 

     8  * Contributors:

     9  *     Nokia Corporation - initial implementation 

    10  *******************************************************************************/

    11 package org.eclipse.ercp.swt.midp;

    12 

    13 import org.eclipse.swt.SWT;

    14 

    15 /**

    16  * <p>

    17  * To use eSWT API a MIDlet needs to dedicate a thread as the UI thread for

    18  * running the event loop. This can't happen in the MIDlet.startApp() because

    19  * it's required by the MIDP specification that the call to startApp() returns

    20  * quickly. Additionally, many native UI toolkits have restrictions for the

    21  * thread that can be used as the UI thread. Thus, a random Java thread can't be

    22  * used either.

    23  * </p>

    24  * <p>

    25  * This class provides means to obtain a thread that can be used as the UI

    26  * thread on the platform. All MIDlets must use this class to obtain the UI

    27  * thread. If a MIDlet uses some other thread as the UI thread then the behavior

    28  * is undefined.

    29  * </p>

    30  * 

    31  * @see MIDlet

    32  * @see MIDlet#startApp

    33  */

    34 public class UIThreadSupport {

    35 

    36 private static boolean started;

    37 

    38 /**

    39  * <p>

    40  * Calls back the given Runnable in a thread that can be used as the UI thread.

    41  * The method must not be called more than once as there might be only one

    42  * thread in the process capable of being used as the UI thread.

    43  * </p>

    44  * 

    45  * An example: <code><pre>

    46  * ...

    47  * class MyMIDlet extends javax.microedition.midlet.MIDlet {

    48  *     ...

    49  *     public void startApp() {

    50  *         UIThreadSupport.startInUIThread(new Runnable() {

    51  *             public void run() {

    52  *                 Display display = new Display();

    53  *                 ...

    54  *             }

    55  *          });

    56  *     }

    57  *     ...

    58  * }

    59  * </pre></code>

    60  * 

    61  * @param runnable The Runnable object to call back

    62  * @exception SWTError <ul>

    63  *                <li>ERROR_NO_HANDLES if a handle could not be obtained for

    64  *                thread creation</li>

    65  * @exception SWTError <ul>

    66  *                <li>ERROR_FAILED_EXEC if called more than once</li>

    67  * @see MIDlet

    68  * @see MIDlet#startApp

    69  */

    70 public static void startInUIThread(Runnable runnable) {

    71     synchronized(UIThreadSupport.class) {

    72         if(started) {

    73             SWT.error(SWT.ERROR_FAILED_EXEC);

    74         }

    75         started = true;

    76     }

    77     try {

    78         new Thread(runnable).start();

    79     } catch(Exception e) {

    80         SWT.error(SWT.ERROR_NO_HANDLES);

    81     }

    82 }

    83 

    84 }