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 
QueuedOperation(Runnable actualRannable)39         public QueuedOperation(Runnable actualRannable) {
40             mActualRannable = actualRannable;
41         }
42 
43         @Override
run()44         public void run() {
45             mPendingOperations.remove(this);
46             mActualRannable.run();
47         }
48 
cancel()49         public void cancel() {
50             mPendingOperations.remove(this);
51             cancelRunnable(this);
52         }
53     }
54 
DelayedOperations(Handler handler)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      */
post(Runnable r)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      */
removeCallbacks(Runnable r)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      */
removeCallbacks()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. */
postRunnable(Runnable r)98     void postRunnable(Runnable r) {
99         mHandler.post(r);
100     }
101 
102     /** Overridden by test, as Handler is not mockable. */
cancelRunnable(Runnable r)103     void cancelRunnable(Runnable r) {
104         mHandler.removeCallbacks(r);
105     }
106 }
107