release相比reset流程，多了一些處理

• MediaPlayer層將MediaPlayer的各種listener置為null
• jni層減少了對surface的引用
• jni層銷毀了mediaplayer的實例
  這里先偷懶，沒詳細分析

    /**
     * Releases resources associated with this MediaPlayer object.
     * It is considered good practice to call this method when you're
     * done using the MediaPlayer. In particular, whenever an Activity
     * of an application is paused (its onPause() method is called),
     * or stopped (its onStop() method is called), this method should be
     * invoked to release the MediaPlayer object, unless the application
     * has a special need to keep the object around. In addition to
     * unnecessary resources (such as memory and instances of codecs)
     * being held, failure to call this method immediately if a
     * MediaPlayer object is no longer needed may also lead to
     * continuous battery consumption for mobile devices, and playback
     * failure for other applications if no multiple instances of the
     * same codec are supported on a device. Even if multiple instances
     * of the same codec are supported, some performance degradation
     * may be expected when unnecessary multiple instances are used
     * at the same time.
     */
    public void release() {
        baseRelease();
        stayAwake(false);
        updateSurfaceScreenOn();
        mOnPreparedListener = null;
        mOnBufferingUpdateListener = null;
        mOnCompletionListener = null;
        mOnSeekCompleteListener = null;
        mOnErrorListener = null;
        mOnInfoListener = null;
        mOnVideoSizeChangedListener = null;
        mOnTimedTextListener = null;
        if (mTimeProvider != null) {
            mTimeProvider.close();
            mTimeProvider = null;
        }
        mOnSubtitleDataListener = null;

        // Modular DRM clean up
        mOnDrmConfigHelper = null;
        mOnDrmInfoHandlerDelegate = null;
        mOnDrmPreparedHandlerDelegate = null;
        resetDrmState();

        _release();
    }

    private native void _release();

static void
android_media_MediaPlayer_release(JNIEnv *env, jobject thiz)
{
    ALOGV("release");
    decVideoSurfaceRef(env, thiz);
    sp<MediaPlayer> mp = setMediaPlayer(env, thiz, 0);
    if (mp != NULL) {
        // this prevents native callbacks after the object is released
        mp->setListener(0);
        mp->disconnect();
    }
}

void MediaPlayer::disconnect()
{
    ALOGV("disconnect");
    sp<IMediaPlayer> p;
    {
        Mutex::Autolock _l(mLock);
        p = mPlayer;
        mPlayer.clear();
    }

    if (p != 0) {
        p->disconnect();
    }
}

void MediaPlayerService::Client::disconnect()
{
    ALOGV("disconnect(%d) from pid %d", mConnId, mPid);
    // grab local reference and clear main reference to prevent future
    // access to object
    sp<MediaPlayerBase> p;
    {
        Mutex::Autolock l(mLock);
        p = mPlayer;
        mClient.clear();
        mPlayer.clear();
    }

    // clear the notification to prevent callbacks to dead client
    // and reset the player. We assume the player will serialize
    // access to itself if necessary.
    if (p != 0) {
        p->setNotifyCallback(0, 0);
#if CALLBACK_ANTAGONIZER
        ALOGD("kill Antagonizer");
        mAntagonizer->kill();
#endif
        p->reset();
    }

    {
        Mutex::Autolock l(mLock);
        disconnectNativeWindow_l();
    }

    IPCThreadState::self()->flushCommands();
}