The Tor Browser: mobile/android/base/util/UiAsyncTask.java@fc2d59ddac77

     1 /* -*- Mode: Java; c-basic-offset: 4; tab-width: 4; indent-tabs-mode: nil; -*-

     2  * This Source Code Form is subject to the terms of the Mozilla Public

     3  * License, v. 2.0. If a copy of the MPL was not distributed with this

     4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     6 package org.mozilla.gecko.util;

     8 import android.os.Handler;

     9 import android.os.Looper;

    11 /**

    12  * Executes a background task and publishes the result on the UI thread.

    13  *

    14  * The standard {@link android.os.AsyncTask} only runs onPostExecute on the

    15  * thread it is constructed on, so this is a convenience class for creating

    16  * tasks off the UI thread.

    17  */

    18 public abstract class UiAsyncTask<Params, Progress, Result> {

    19     private volatile boolean mCancelled = false;

    20     private final Handler mBackgroundThreadHandler;

    21     private static Handler sHandler;

    23     /**

    24      * Creates a new asynchronous task.

    25      *

    26      * @param backgroundThreadHandler the handler to execute the background task on

    27      */

    28     public UiAsyncTask(Handler backgroundThreadHandler) {

    29         mBackgroundThreadHandler = backgroundThreadHandler;

    30     }

    32     private static synchronized Handler getUiHandler() {

    33         if (sHandler == null) {

    34             sHandler = new Handler(Looper.getMainLooper());

    35         }

    36         return sHandler;

    37     }

    39     private final class BackgroundTaskRunnable implements Runnable {

    40         private Params[] mParams;

    42         public BackgroundTaskRunnable(Params... params) {

    43             mParams = params;

    44         }

    46         @Override

    47         public void run() {

    48             final Result result = doInBackground(mParams);

    50             getUiHandler().post(new Runnable() {

    51                 @Override

    52                 public void run() {

    53                     if (mCancelled)

    54                         onCancelled();

    55                     else

    56                         onPostExecute(result);

    57                 }

    58             });

    59         }

    60     }

    62     public final void execute(final Params... params) {

    63         getUiHandler().post(new Runnable() {

    64             @Override

    65             public void run() {

    66                 onPreExecute();

    67                 mBackgroundThreadHandler.post(new BackgroundTaskRunnable(params));

    68             }

    69         });

    70     }

    72     @SuppressWarnings({"UnusedParameters"})

    73     public final boolean cancel(boolean mayInterruptIfRunning) {

    74         mCancelled = true;

    75         return mCancelled;

    76     }

    78     public final boolean isCancelled() {

    79         return mCancelled;

    80     }

    82     protected void onPreExecute() { }

    83     protected void onPostExecute(Result result) { }

    84     protected void onCancelled() { }

    85     protected abstract Result doInBackground(Params... params);

    86 }

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