MockLooper.java revision 72c639e8b97067e948eca8be50dfea3173121090 
1/*
2 * Copyright (C) 2015 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.server.wifi;
18
19import static org.junit.Assert.assertTrue;
20
21import android.os.Looper;
22import android.os.Message;
23import android.os.MessageQueue;
24
25import java.lang.reflect.Constructor;
26import java.lang.reflect.Field;
27import java.lang.reflect.InvocationTargetException;
28import java.lang.reflect.Method;
29
30/**
31 * Creates a looper whose message queue can be manipulated
32 * This allows testing code that uses a looper to dispatch messages in a deterministic manner
33 * Creating a MockLooper will also install it as the looper for the current thread
34 */
35public class MockLooper {
36    private final Looper mLooper;
37
38    private static final Constructor<Looper> LOOPER_CONSTRUCTOR;
39    private static final Field THREAD_LOCAL_LOOPER_FIELD;
40    private static final Method MESSAGE_QUEUE_NEXT_METHOD;
41
42    static {
43        try {
44            LOOPER_CONSTRUCTOR = Looper.class.getDeclaredConstructor(Boolean.TYPE);
45            LOOPER_CONSTRUCTOR.setAccessible(true);
46            THREAD_LOCAL_LOOPER_FIELD = Looper.class.getDeclaredField("sThreadLocal");
47            THREAD_LOCAL_LOOPER_FIELD.setAccessible(true);
48            MESSAGE_QUEUE_NEXT_METHOD = MessageQueue.class.getDeclaredMethod("next");
49            MESSAGE_QUEUE_NEXT_METHOD.setAccessible(true);
50        } catch (NoSuchFieldException | NoSuchMethodException e) {
51            throw new RuntimeException("Failed to initialize MockLooper", e);
52        }
53    }
54
55
56    public MockLooper() throws Exception {
57        mLooper = LOOPER_CONSTRUCTOR.newInstance(false);
58
59        ThreadLocal<Looper> threadLocalLooper =
60                (ThreadLocal<Looper>) THREAD_LOCAL_LOOPER_FIELD.get(null);
61        threadLocalLooper.set(mLooper);
62    }
63
64    public Looper getLooper() {
65        return mLooper;
66    }
67
68    private Message messageQueueNext() {
69        try {
70            return (Message) MESSAGE_QUEUE_NEXT_METHOD.invoke(mLooper.getQueue());
71        } catch (IllegalAccessException | InvocationTargetException e) {
72            throw new RuntimeException("Reflection error when getting next message", e);
73        }
74    }
75
76    /**
77     * @return true if there are pending messages in the message queue
78     */
79    public boolean hasMessage() {
80        return !mLooper.getQueue().isIdle();
81    }
82
83    /**
84     * @return the next message in the Looper's message queue or null if there is none
85     */
86    public Message nextMessage() {
87        if (hasMessage()) {
88            return messageQueueNext();
89        } else {
90            return null;
91        }
92    }
93
94    /**
95     * Dispatch the next message in the queue
96     * Asserts that there is a message in the queue
97     */
98    public void dispatchNext() {
99        assertTrue(hasMessage());
100        Message msg = messageQueueNext();
101        if (msg == null) {
102            return;
103        }
104        msg.getTarget().dispatchMessage(msg);
105    }
106
107    /**
108     * Dispatch all messages currently in the queue
109     * Will not fail if there are no messages pending
110     * @return the number of messages dispatched
111     */
112    public int dispatchAll() {
113        int count = 0;
114        while (hasMessage()) {
115            dispatchNext();
116            ++count;
117        }
118        return count;
119    }
120}
121