frameworks/base/media/java/android/media/MediaPlayer.java

    /**
     * Resets the MediaPlayer to its uninitialized state. After calling
     * this method, you will have to initialize it again by setting the
     * data source and calling prepare().
     */
    public void reset() {
        mSelectedSubtitleTrackIndex = -1;
        synchronized(mOpenSubtitleSources) {
            for (final InputStream is: mOpenSubtitleSources) {
                try {
                    is.close();
                } catch (IOException e) {
                }
            }
            mOpenSubtitleSources.clear();
        }
        if (mSubtitleController != null) {
            mSubtitleController.reset();
        }
        if (mTimeProvider != null) {
            mTimeProvider.close();
            mTimeProvider = null;
        }

        stayAwake(false);
        _reset();
        // make sure none of the listeners get called anymore
        if (mEventHandler != null) {
            mEventHandler.removeCallbacksAndMessages(null);
        }

        synchronized (mIndexTrackPairs) {
            mIndexTrackPairs.clear();
            mInbandTrackIndices.clear();
        };

        resetDrmState();
    }

    private native void _reset();

主要步驟

• 銷毀 Subtitle相關處理
• 銷毀 mTimeProvider
• stayAwake(false)，不保持屏幕長開的的狀態
• _reset()，調用到jni層，下面分析
• 銷毀 mEventHandler所有消息，不再向播放器應用發送任何消息

frameworks/base/media/jni/android_media_MediaPlayer.cpp

static void
android_media_MediaPlayer_reset(JNIEnv *env, jobject thiz)
{
    ALOGV("reset");
    sp<MediaPlayer> mp = getMediaPlayer(env, thiz);
    if (mp == NULL ) {
        jniThrowException(env, "java/lang/IllegalStateException", NULL);
        return;
    }
    process_media_player_call( env, thiz, mp->reset(), NULL, NULL );
}

frameworks/av/media/libmedia/mediaplayer.cpp

status_t MediaPlayer::reset_l()
{
    mLoop = false;
    if (mCurrentState == MEDIA_PLAYER_IDLE) return NO_ERROR;
    mPrepareSync = false;
    if (mPlayer != 0) {
        status_t ret = mPlayer->reset();
        if (ret != NO_ERROR) {
            ALOGE("reset() failed with return code (%d)", ret);
            mCurrentState = MEDIA_PLAYER_STATE_ERROR;
        } else {
            mPlayer->disconnect();
            mCurrentState = MEDIA_PLAYER_IDLE;
        }
        // setDataSource has to be called again to create a
        // new mediaplayer.
        mPlayer = 0;
        mCurrentBufferingSettings = BufferingSettings();
        return ret;
    }
    clear_l();
    return NO_ERROR;
}

主要步驟：

• 調用MediaPlayerService 的reset方法
  這一步主要執行到NuPlayer的reset
• 調用MediaPlayerService 的disconnect
  這一步會銷毀MediaPlayerService 保存的服務端mediaplayer binder實例mClient
  和NuPlayer的實例
• 將mPlayer銷毀
  mPlayer是mediaplayer 同服務端MediaPlayerService

frameworks/av/media/libmediaplayerservice/MediaPlayerService.cpp

status_t MediaPlayerService::Client::reset()
{
    ALOGV("[%d] reset", mConnId);
    mMaybeVideoAlive = false;
    mRetransmitEndpointValid = false;
    sp<MediaPlayerBase> p = getPlayer();
    if (p == 0) return UNKNOWN_ERROR;
    return p->reset();
}

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);
       //使用了一個局部變量對mPlayer引用，即對底層播放器的引用。
       //會使強引用計數加1。在這個函數退出后，p的生命周期也結束，智能指針會自動銷毀底層播放器實例
        p = mPlayer;

       //調用了智能指針的clear方法，將強引用計數減1，并m_ptr = 0 
       //mClient 為sp<IMediaPlayerClient>，即是對mediaplayer的引用
       //mPlayer 為sp<MediaPlayerBase>
       //mClient和mPlayer為全局的引用變量，使用clear后， mClient和mPlayer將無法再被使用
        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();
}

disconnect步驟稍微有點繞。先用一個局部變量p 指向了mPlayer，即增加了對NuPlayer的強引用計數，接著銷毀了全局變量mClient和mPlayer引用。mClient計數應該會為0，所以對應的實例也會被銷毀。而NuPlayer的引用計數由于局部變量p，引用計數不會為0。接著通過p 將NuPlayer的回調函數置為0，并調用到NuPlayer的reset方法，這里是重復調用了reset方法，因為release流程只會調用mediaplayer的disconnect方法，不會調用到reset方法。在函數執行完后，局部變量p會自動銷毀，同時也會自動銷毀NuPlayer實例
主要步驟：

• 銷毀mClient和mPlayer的引用
• 設置NuPlayer的回調函數為0
• 調用NuPlayer reset方法
• disconnectNativeWindow_l（沒詳細研究，應該是涉及到顯示的window，跟surface和wms相關）
• flushCommands() 調用talkWithDriver(false)立即發送mOut緩存中的命令數據