michael@0: /* -*- Mode: Java; c-basic-offset: 4; tab-width: 4; indent-tabs-mode: nil; -*-
michael@0:  * This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: package org.mozilla.gecko.util;
michael@0: 
michael@0: import android.os.Handler;
michael@0: import android.os.Looper;
michael@0: 
michael@0: /**
michael@0:  * Executes a background task and publishes the result on the UI thread.
michael@0:  *
michael@0:  * The standard {@link android.os.AsyncTask} only runs onPostExecute on the
michael@0:  * thread it is constructed on, so this is a convenience class for creating
michael@0:  * tasks off the UI thread.
michael@0:  */
michael@0: public abstract class UiAsyncTask<Params, Progress, Result> {
michael@0:     private volatile boolean mCancelled = false;
michael@0:     private final Handler mBackgroundThreadHandler;
michael@0:     private static Handler sHandler;
michael@0: 
michael@0:     /**
michael@0:      * Creates a new asynchronous task.
michael@0:      *
michael@0:      * @param backgroundThreadHandler the handler to execute the background task on
michael@0:      */
michael@0:     public UiAsyncTask(Handler backgroundThreadHandler) {
michael@0:         mBackgroundThreadHandler = backgroundThreadHandler;
michael@0:     }
michael@0: 
michael@0:     private static synchronized Handler getUiHandler() {
michael@0:         if (sHandler == null) {
michael@0:             sHandler = new Handler(Looper.getMainLooper());
michael@0:         }
michael@0:         return sHandler;
michael@0:     }
michael@0: 
michael@0:     private final class BackgroundTaskRunnable implements Runnable {
michael@0:         private Params[] mParams;
michael@0: 
michael@0:         public BackgroundTaskRunnable(Params... params) {
michael@0:             mParams = params;
michael@0:         }
michael@0: 
michael@0:         @Override
michael@0:         public void run() {
michael@0:             final Result result = doInBackground(mParams);
michael@0: 
michael@0:             getUiHandler().post(new Runnable() {
michael@0:                 @Override
michael@0:                 public void run() {
michael@0:                     if (mCancelled)
michael@0:                         onCancelled();
michael@0:                     else
michael@0:                         onPostExecute(result);
michael@0:                 }
michael@0:             });
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     public final void execute(final Params... params) {
michael@0:         getUiHandler().post(new Runnable() {
michael@0:             @Override
michael@0:             public void run() {
michael@0:                 onPreExecute();
michael@0:                 mBackgroundThreadHandler.post(new BackgroundTaskRunnable(params));
michael@0:             }
michael@0:         });
michael@0:     }
michael@0: 
michael@0:     @SuppressWarnings({"UnusedParameters"})
michael@0:     public final boolean cancel(boolean mayInterruptIfRunning) {
michael@0:         mCancelled = true;
michael@0:         return mCancelled;
michael@0:     }
michael@0: 
michael@0:     public final boolean isCancelled() {
michael@0:         return mCancelled;
michael@0:     }
michael@0: 
michael@0:     protected void onPreExecute() { }
michael@0:     protected void onPostExecute(Result result) { }
michael@0:     protected void onCancelled() { }
michael@0:     protected abstract Result doInBackground(Params... params);
michael@0: }