DeferredHandler.java revision dca661236c73ecd819cfea964c6f8170e5cc40ae 
1/*
2 * Copyright (C) 2008 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
17package com.android.launcher2;
18
19import android.os.Handler;
20import android.os.Looper;
21import android.os.Message;
22import android.os.MessageQueue;
23import android.util.Log;
24
25import java.util.LinkedList;
26
27/**
28 * Queue of things to run on a looper thread.  Items posted with {@link #post} will not
29 * be actually enqued on the handler until after the last one has run, to keep from
30 * starving the thread.
31 *
32 * This class is fifo.
33 */
34public class DeferredHandler {
35    private LinkedList<Runnable> mQueue = new LinkedList();
36    private MessageQueue mMessageQueue = Looper.myQueue();
37    private Impl mHandler = new Impl();
38
39    private class Impl extends Handler implements MessageQueue.IdleHandler {
40        public void handleMessage(Message msg) {
41            Runnable r;
42            synchronized (mQueue) {
43                if (mQueue.size() == 0) {
44                    return;
45                }
46                r = mQueue.removeFirst();
47            }
48            r.run();
49            synchronized (mQueue) {
50                scheduleNextLocked();
51            }
52        }
53
54        public boolean queueIdle() {
55            handleMessage(null);
56            return false;
57        }
58    }
59
60    private class IdleRunnable implements Runnable {
61        Runnable mRunnable;
62
63        IdleRunnable(Runnable r) {
64            mRunnable = r;
65        }
66
67        public void run() {
68            mRunnable.run();
69        }
70    }
71
72    public DeferredHandler() {
73    }
74
75    /** Schedule runnable to run after everything that's on the queue right now. */
76    public void post(Runnable runnable) {
77        synchronized (mQueue) {
78            mQueue.add(runnable);
79            if (mQueue.size() == 1) {
80                scheduleNextLocked();
81            }
82        }
83    }
84
85    /** Schedule runnable to run when the queue goes idle. */
86    public void postIdle(final Runnable runnable) {
87        post(new IdleRunnable(runnable));
88    }
89
90    public void cancelRunnable(Runnable runnable) {
91        synchronized (mQueue) {
92            while (mQueue.remove(runnable)) { }
93        }
94    }
95
96    public void cancel() {
97        synchronized (mQueue) {
98            mQueue.clear();
99        }
100    }
101
102    void scheduleNextLocked() {
103        if (mQueue.size() > 0) {
104            Runnable peek = mQueue.getFirst();
105            if (peek instanceof IdleRunnable) {
106                mMessageQueue.addIdleHandler(mHandler);
107            } else {
108                mHandler.sendEmptyMessage(1);
109            }
110        }
111    }
112}
113
114