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      1 /*
      2  * Copyright (C) 2011 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.emailcommon.utility;
     18 
     19 import com.google.common.annotations.VisibleForTesting;
     20 
     21 import android.os.Handler;
     22 
     23 import java.util.ArrayList;
     24 import java.util.LinkedList;
     25 
     26 /**
     27  * Class that helps post {@link Runnable}s to a {@link Handler}, and cancel pending ones
     28  * at once.
     29  */
     30 public class DelayedOperations {
     31     private final Handler mHandler;
     32 
     33     @VisibleForTesting
     34     final LinkedList<QueuedOperation> mPendingOperations = new LinkedList<QueuedOperation>();
     35 
     36     private class QueuedOperation implements Runnable {
     37         private final Runnable mActualRannable;
     38 
     39         public QueuedOperation(Runnable actualRannable) {
     40             mActualRannable = actualRannable;
     41         }
     42 
     43         @Override
     44         public void run() {
     45             mPendingOperations.remove(this);
     46             mActualRannable.run();
     47         }
     48 
     49         public void cancel() {
     50             mPendingOperations.remove(this);
     51             cancelRunnable(this);
     52         }
     53     }
     54 
     55     public DelayedOperations(Handler handler) {
     56         mHandler = handler;
     57     }
     58 
     59     /**
     60      * Post a {@link Runnable} to the handler.  Equivalent to {@link Handler#post(Runnable)}.
     61      */
     62     public void post(Runnable r) {
     63         final QueuedOperation qo = new QueuedOperation(r);
     64         mPendingOperations.add(qo);
     65         postRunnable(qo);
     66     }
     67 
     68     /**
     69      * Cancel a runnable that's been posted with {@link #post(Runnable)}.
     70      *
     71      * Equivalent to {@link Handler#removeCallbacks(Runnable)}.
     72      */
     73     public void removeCallbacks(Runnable r) {
     74         QueuedOperation found = null;
     75         for (QueuedOperation qo : mPendingOperations) {
     76             if (qo.mActualRannable == r) {
     77                 found = qo;
     78                 break;
     79             }
     80         }
     81         if (found != null) {
     82             found.cancel();
     83         }
     84     }
     85 
     86     /**
     87      * Cancel all pending {@link Runnable}s.
     88      */
     89     public void removeCallbacks() {
     90         // To avoid ConcurrentModificationException
     91         final ArrayList<QueuedOperation> temp = new ArrayList<QueuedOperation>(mPendingOperations);
     92         for (QueuedOperation qo : temp) {
     93             qo.cancel();
     94         }
     95     }
     96 
     97     /** Overridden by test, as Handler is not mockable. */
     98     void postRunnable(Runnable r) {
     99         mHandler.post(r);
    100     }
    101 
    102     /** Overridden by test, as Handler is not mockable. */
    103     void cancelRunnable(Runnable r) {
    104         mHandler.removeCallbacks(r);
    105     }
    106 }
    107