mediaplayer播放过程及player的选择

还是先来看个序列图：

１media.player的加载

int main(int argc __unused, char **argv __unused)
{
   
    signal(SIGPIPE, SIG_IGN);

    sp<ProcessState> proc(ProcessState::self());
    sp<IServiceManager> sm(defaultServiceManager());
    ALOGI("ServiceManager: %p", sm.get());
    InitializeIcuOrDie();
    MediaPlayerService::instantiate();
    ResourceManagerService::instantiate();
    registerExtensions();
    ProcessState::self()->startThreadPool();
    IPCThreadState::self()->joinThreadPool();
}
void MediaPlayerService::instantiate() {
   
    defaultServiceManager()->addService(
            String16("media.player"), new MediaPlayerService());
}

这些文件会被编译成so库文件，在rc资源文件里面进行首次加载，拉起media.player服务

２.MediaPlayerService构造函数

MediaPlayerService::MediaPlayerService()
{
   
    ALOGV("MediaPlayerService created");
    mNextConnId = 1;

    MediaPlayerFactory::registerBuiltinFactories();
}

void MediaPlayerFactory::registerBuiltinFactories() {
   
    Mutex::Autolock lock_(&sLock);

    if (sInitComplete)
        return;

    registerFactory_l(new NuPlayerFactory(), NU_PLAYER);
    registerFactory_l(new TestPlayerFactory(), TEST_PLAYER);

    sInitComplete = true;
}

在其构造函数里面，主要是添加各种player到map里面，一般情况下OEM或者自定义的player就是在这里添加的。上面的代码实际上只有一个播放器，没得选择。一般情况下会有多个player以供选择，根据需要播放的文件类型来选择最合适的播放器

3.MediaPlayer

我们一般使用MediaPlayer这个类来播放音视频文件，来看看其构造函数

    public MediaPlayer() {
   
        super(new AudioAttributes.Builder().build(),
                AudioPlaybackConfiguration.PLAYER_TYPE_JAM_MEDIAPLAYER);

        Looper looper;
        if ((looper = Looper.myLooper()) != null) {
   
            mEventHandler = new EventHandler(this, looper);
        } else if ((looper = Looper.getMainLooper()) != null) {
   
            mEventHandler = new EventHandler(this, looper);
        } else {
   
            mEventHandler = null;
        }

        mTimeProvider = new TimeProvider(this);
        mOpenSubtitleSources = new Vector<InputStream>();

        /* Native setup requires a weak reference to our object.
         * It's easier to create it here than in C++.
         */
        native_setup(new WeakReference<MediaPlayer>(this));

        baseRegisterPlayer();
    }

上面的handle消息处理不关心，这里主要看native_setup这个JNI函数的调用，看其干了什么

4.native_setup

android_media_MediaPlayer_native_setup(JNIEnv *env, jobject thiz, jobject weak_this)