1/*
2 * Copyright (C) 2006 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 android.os;
18
19/**
20 * Handy class for starting a new thread that has a looper. The looper can then be
21 * used to create handler classes. Note that start() must still be called.
22 */
23public class HandlerThread extends Thread {
24    int mPriority;
25    int mTid = -1;
26    Looper mLooper;
27
28    public HandlerThread(String name) {
29        super(name);
30        mPriority = Process.THREAD_PRIORITY_DEFAULT;
31    }
32
33    /**
34     * Constructs a HandlerThread.
35     * @param name
36     * @param priority The priority to run the thread at. The value supplied must be from
37     * {@link android.os.Process} and not from java.lang.Thread.
38     */
39    public HandlerThread(String name, int priority) {
40        super(name);
41        mPriority = priority;
42    }
43
44    /**
45     * Call back method that can be explicitly overridden if needed to execute some
46     * setup before Looper loops.
47     */
48    protected void onLooperPrepared() {
49    }
50
51    @Override
52    public void run() {
53        mTid = Process.myTid();
54        Looper.prepare();
55        synchronized (this) {
56            mLooper = Looper.myLooper();
57            notifyAll();
58        }
59        Process.setThreadPriority(mPriority);
60        onLooperPrepared();
61        Looper.loop();
62        mTid = -1;
63    }
64
65    /**
66     * This method returns the Looper associated with this thread. If this thread not been started
67     * or for any reason is isAlive() returns false, this method will return null. If this thread
68     * has been started, this method will block until the looper has been initialized.
69     * @return The looper.
70     */
71    public Looper getLooper() {
72        if (!isAlive()) {
73            return null;
74        }
75
76        // If the thread has been started, wait until the looper has been created.
77        synchronized (this) {
78            while (isAlive() && mLooper == null) {
79                try {
80                    wait();
81                } catch (InterruptedException e) {
82                }
83            }
84        }
85        return mLooper;
86    }
87
88    /**
89     * Quits the handler thread's looper.
90     * <p>
91     * Causes the handler thread's looper to terminate without processing any
92     * more messages in the message queue.
93     * </p><p>
94     * Any attempt to post messages to the queue after the looper is asked to quit will fail.
95     * For example, the {@link Handler#sendMessage(Message)} method will return false.
96     * </p><p class="note">
97     * Using this method may be unsafe because some messages may not be delivered
98     * before the looper terminates.  Consider using {@link #quitSafely} instead to ensure
99     * that all pending work is completed in an orderly manner.
100     * </p>
101     *
102     * @return True if the looper looper has been asked to quit or false if the
103     * thread had not yet started running.
104     *
105     * @see #quitSafely
106     */
107    public boolean quit() {
108        Looper looper = getLooper();
109        if (looper != null) {
110            looper.quit();
111            return true;
112        }
113        return false;
114    }
115
116    /**
117     * Quits the handler thread's looper safely.
118     * <p>
119     * Causes the handler thread's looper to terminate as soon as all remaining messages
120     * in the message queue that are already due to be delivered have been handled.
121     * Pending delayed messages with due times in the future will not be delivered.
122     * </p><p>
123     * Any attempt to post messages to the queue after the looper is asked to quit will fail.
124     * For example, the {@link Handler#sendMessage(Message)} method will return false.
125     * </p><p>
126     * If the thread has not been started or has finished (that is if
127     * {@link #getLooper} returns null), then false is returned.
128     * Otherwise the looper is asked to quit and true is returned.
129     * </p>
130     *
131     * @return True if the looper looper has been asked to quit or false if the
132     * thread had not yet started running.
133     */
134    public boolean quitSafely() {
135        Looper looper = getLooper();
136        if (looper != null) {
137            looper.quitSafely();
138            return true;
139        }
140        return false;
141    }
142
143    /**
144     * Returns the identifier of this thread. See Process.myTid().
145     */
146    public int getThreadId() {
147        return mTid;
148    }
149}
150