MediaController之skipToPrevious()源码简介

mMediaController.getTransportControls().skipToNext();

mMediaController = new MediaController(MainActivity.this, mMediaBrowser.getSessionToken());
mMediaController.getTransportControls().skipToNext();

frameworks\base\media\java\android\media\session\MediaController.java

public MediaController(@NonNull Context context, @NonNull MediaSession.Token token) {
    if (context == null) {
        throw new IllegalArgumentException("context shouldn't be null");
    }
    if (token == null) {
        throw new IllegalArgumentException("token shouldn't be null");
    }
    if (token.getBinder() == null) {
        throw new IllegalArgumentException("token.getBinder() shouldn't be null");
    }
    //获取的是token中的Binder对象
    mSessionBinder = token.getBinder();
    //创建TransportControls对象
    mTransportControls = new TransportControls();
    mToken = token;
    mContext = context;
}

public @NonNull TransportControls getTransportControls() {
    return mTransportControls;
}

public void skipToNext() {
    try {
        mSessionBinder.next(mContext.getPackageName());
    } catch (RemoteException e) {
        Log.wtf(TAG, "Error calling next.", e);
    }
}

//通过MediaSession.Token的对象获取的
mSessionBinder = token.getBinder();

\frameworks\base\media\java\android\media\browse\MediaBrowser.java

public @NonNull MediaSession.Token getSessionToken() {
    if (!isConnected()) {
        throw new IllegalStateException("getSessionToken() called while not connected (state="
                + mState + ")");
    }
    return mMediaSessionToken;
}

private void onServiceConnected(final IMediaBrowserServiceCallbacks callback,
        final String root, final MediaSession.Token session, final Bundle extra) {
    mHandler.post(new Runnable() {
        @Override
        public void run() {
            if (!isCurrent(callback, "onConnect")) {
                return;
            }
            if (mState != CONNECT_STATE_CONNECTING) {
                Log.w(TAG, "onConnect from service while mState="
                        + getStateLabel(mState) + "... ignoring");
                return;
            }
            mRootId = root;
            //这里赋值的，
            mMediaSessionToken = session;
            mExtras = extra;
            mState = CONNECT_STATE_CONNECTED;
            mCallback.onConnected();
           //略
        }
    });
}
​

private static class ServiceCallbacks extends IMediaBrowserServiceCallbacks.Stub {
    private WeakReference<MediaBrowser> mMediaBrowser;
​
    ServiceCallbacks(MediaBrowser mediaBrowser) {
        mMediaBrowser = new WeakReference<MediaBrowser>(mediaBrowser);
    }
   //略
}

private static class ServiceCallbacks extends IMediaBrowserServiceCallbacks.Stub {
    private WeakReference<MediaBrowser> mMediaBrowser;
    ServiceCallbacks(MediaBrowser mediaBrowser) {
        mMediaBrowser = new WeakReference<MediaBrowser>(mediaBrowser);
    }
    
    @Override
    public void onConnect(String root, MediaSession.Token session,
            final Bundle extras) {
        MediaBrowser mediaBrowser = mMediaBrowser.get();
        Log.d(TAG,"onConnect 1 mediaBrowser: "+ mediaBrowser);
        if (mediaBrowser != null) {
            mediaBrowser.onServiceConnected(this, root, session, extras);
        }
    }
​
    @Override
    public void onConnectFailed() {
        MediaBrowser mediaBrowser = mMediaBrowser.get();
        if (mediaBrowser != null) {
            mediaBrowser.onConnectionFailed(this);
        }
    }
    //略
}