Android Audio代码分析16 - testPlaybackHeadPositionAfterPause函数

play, stop, flush这几个函数，今天来看看pause函数。


*****************************************源码*************************************************

    //Test case 4: getPlaybackHeadPosition() is > 0 after play(); pause();
    @LargeTest
    public void testPlaybackHeadPositionAfterPause() throws Exception {
        // constants for test
        final String TEST_NAME = "testPlaybackHeadPositionAfterPause";
        final int TEST_SR = 22050;
        final int TEST_CONF = AudioFormat.CHANNEL_OUT_STEREO;
        final int TEST_FORMAT = AudioFormat.ENCODING_PCM_16BIT;
        final int TEST_MODE = AudioTrack.MODE_STREAM;
        final int TEST_STREAM_TYPE = AudioManager.STREAM_MUSIC;
        
        //-------- initialization --------------
        int minBuffSize = AudioTrack.getMinBufferSize(TEST_SR, TEST_CONF, TEST_FORMAT);
        AudioTrack track = new AudioTrack(TEST_STREAM_TYPE, TEST_SR, TEST_CONF, TEST_FORMAT, 
                minBuffSize, TEST_MODE);
        byte data[] = new byte[minBuffSize/2];
        //--------    test        --------------
        assumeTrue(TEST_NAME, track.getState() == AudioTrack.STATE_INITIALIZED);
        track.write(data, 0, data.length);
        track.write(data, 0, data.length);
        track.play();
        Thread.sleep(100);
        track.pause();
        int pos = track.getPlaybackHeadPosition();
        log(TEST_NAME, "position ="+ pos);
        assertTrue(TEST_NAME, pos > 0);
        //-------- tear down      --------------
        track.release();
    }

**********************************************************************************************
源码路径：
frameworks\base\media\tests\mediaframeworktest\src\com\android\mediaframeworktest\functional\MediaAudioTrackTest.java


#######################说明################################

    //Test case 4: getPlaybackHeadPosition() is > 0 after play(); pause();
    @LargeTest
    public void testPlaybackHeadPositionAfterPause() throws Exception {
        // constants for test
        final String TEST_NAME = "testPlaybackHeadPositionAfterPause";
        final int TEST_SR = 22050;
        final int TEST_CONF = AudioFormat.CHANNEL_OUT_STEREO;
        final int TEST_FORMAT = AudioFormat.ENCODING_PCM_16BIT;
        final int TEST_MODE = AudioTrack.MODE_STREAM;
        final int TEST_STREAM_TYPE = AudioManager.STREAM_MUSIC;
        
        //-------- initialization --------------
        int minBuffSize = AudioTrack.getMinBufferSize(TEST_SR, TEST_CONF, TEST_FORMAT);
        AudioTrack track = new AudioTrack(TEST_STREAM_TYPE, TEST_SR, TEST_CONF, TEST_FORMAT, 
                minBuffSize, TEST_MODE);
        byte data[] = new byte[minBuffSize/2];
        //--------    test        --------------
        assumeTrue(TEST_NAME, track.getState() == AudioTrack.STATE_INITIALIZED);
        track.write(data, 0, data.length);
        track.write(data, 0, data.length);
        track.play();
        Thread.sleep(100);
        track.pause();
// ++++++++++++++++++++++++++++++pause++++++++++++++++++++++++++++++++++
    /**
     * Pauses the playback of the audio data.
     * @throws IllegalStateException
     */
    public void pause()
    throws IllegalStateException {
        if (mState != STATE_INITIALIZED) {
            throw(new IllegalStateException("pause() called on uninitialized AudioTrack."));
        }
        //logd("pause()");


        // pause playback
        synchronized(mPlayStateLock) {
            native_pause();
// +++++++++++++++++++++++++++++++android_media_AudioTrack_pause+++++++++++++++++++++++++++++++++
static void
android_media_AudioTrack_pause(JNIEnv *env, jobject thiz)
{
    AudioTrack *lpTrack = (AudioTrack *)env->GetIntField(
        thiz, javaAudioTrackFields.nativeTrackInJavaObj);
    if (lpTrack == NULL ) {
        jniThrowException(env, "java/lang/IllegalStateException",
            "Unable to retrieve AudioTrack pointer for pause()");
        return;
    }


    lpTrack->pause();
// ++++++++++++++++++++++++++++++AudioTrack::pause++++++++++++++++++++++++++++++++++
void AudioTrack::pause()
{
    LOGV("pause");
    if (android_atomic_and(~1, &mActive) == 1) {
// mAudioTrack在函数AudioTrack::createTrack中被赋值，其最终指向的其实是一个TrackHandle对象
        mAudioTrack->pause();
// ++++++++++++++++++++++++++++AudioFlinger::TrackHandle::pause++++++++++++++++++++++++++++++++++++
void AudioFlinger::TrackHandle::pause() {
    mTrack->pause();
// ++++++++++++++++++++++++++++AudioFlinger::PlaybackThread::Track::pause++++++++++++++++++++++++++++++++++++
void AudioFlinger::PlaybackThread::Track::pause()
{
    LOGV("pause(%d), calling thread %d", mName, IPCThreadState::self()->getCallingPid());
    sp<ThreadBase> thread = mThread.promote();
    if (thread != 0) {
        Mutex::Autolock _l(thread->mLock);
        if (mState == ACTIVE || mState == RESUMING) {
            mState = PAUSING;
            LOGV("ACTIVE/RESUMING => PAUSING (%d) on thread %p", mName, thread.get());
            if (!isOutputTrack()) {
// ++++++++++++++++++++++++++++isOutputTrack++++++++++++++++++++++++++++++++++++
            bool isOutputTrack() const {
                return (mStreamType == AudioSystem::NUM_STREAM_TYPES);
            }
// ----------------------------isOutputTrack------------------------------------
                thread->mLock.unlock();
// 在看stop代码的时候已经看过函数AudioSystem::stopOutput
                AudioSystem::stopOutput(thread->id(),
                                        (AudioSystem::stream_type)mStreamType,
                                        mSessionId);
                thread->mLock.lock();
            }
        }
    }
}
// ----------------------------AudioFlinger::PlaybackThread::Track::pause------------------------------------
}
// ----------------------------AudioFlinger::TrackHandle::pause------------------------------------
    }
}
// ------------------------------AudioTrack::pause----------------------------------
}
// -------------------------------android_media_AudioTrack_pause---------------------------------
            mPlayState = PLAYSTATE_PAUSED;
        }
    }
// ------------------------------pause----------------------------------
        int pos = track.getPlaybackHeadPosition();
        log(TEST_NAME, "position ="+ pos);
        assertTrue(TEST_NAME, pos > 0);
        //-------- tear down      --------------
        track.release();
// ++++++++++++++++++++++++++++++release++++++++++++++++++++++++++++++++++
    /**
     * Releases the native AudioTrack resources.
     */
    public void release() {
        // even though native_release() stops the native AudioTrack, we need to stop
        // AudioTrack subclasses too.
        try {
            stop();
        } catch(IllegalStateException ise) { 
            // don't raise an exception, we're releasing the resources.
        }
        native_release();
// +++++++++++++++++++++++++++++android_media_AudioTrack_native_release+++++++++++++++++++++++++++++++++++
static void android_media_AudioTrack_native_release(JNIEnv *env,  jobject thiz) {
       
    // do everything a call to finalize would
    android_media_AudioTrack_native_finalize(env, thiz);
+++++++++++++++++++++++++++++android_media_AudioTrack_native_finalize+++++++++++++++++++++++++++++++++++
// static void android_media_AudioTrack_native_finalize(JNIEnv *env,  jobject thiz) {
    //LOGV("android_media_AudioTrack_native_finalize jobject: %x\n", (int)thiz);
       
    // delete the AudioTrack object
    AudioTrack *lpTrack = (AudioTrack *)env->GetIntField(
        thiz, javaAudioTrackFields.nativeTrackInJavaObj);
    if (lpTrack) {
        //LOGV("deleting lpTrack: %x\n", (int)lpTrack);
        lpTrack->stop();
        delete lpTrack;
    }
    
    // delete the JNI data
    AudioTrackJniStorage* pJniStorage = (AudioTrackJniStorage *)env->GetIntField(
        thiz, javaAudioTrackFields.jniData);
    if (pJniStorage) {
        // delete global refs created in native_setup
        env->DeleteGlobalRef(pJniStorage->mCallbackData.audioTrack_class);
        env->DeleteGlobalRef(pJniStorage->mCallbackData.audioTrack_ref);
        //LOGV("deleting pJniStorage: %x\n", (int)pJniStorage);
        delete pJniStorage;
    }
}
// -----------------------------android_media_AudioTrack_native_finalize-----------------------------------
    // + reset the native resources in the Java object so any attempt to access
    // them after a call to release fails.
    env->SetIntField(thiz, javaAudioTrackFields.nativeTrackInJavaObj, 0);
    env->SetIntField(thiz, javaAudioTrackFields.jniData, 0);
}
// -----------------------------android_media_AudioTrack_native_release-----------------------------------
        mState = STATE_UNINITIALIZED;
    }
// ------------------------------release----------------------------------
    }

###########################################################


&&&&&&&&&&&&&&&&&&&&&&&总结&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
pause与stop类似，都会调用函数AudioSystem::stopOutput。
差别是，stop会reset，也就是将audio_track_cblk_t中的user, server等清0。
而pause不会。


这也就是在播放的时候，按暂停，播放进度条会停在当前位置不动，按停止的话，进度条则回到了初始状态。
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