无法故意绑定MediaPlaybackService，并且无法检测到MediaSessionCompat.Callbacks

编程问答 2022-08-14

问题描述

我一直在尝试借助服务来检测蓝牙耳机的媒体按键事件，但该应用程序崩溃并出现以下错误：

java.lang.RuntimeException: Unable to bind to service pk.mohammadadnan.tunalapp.MediaPlaybackService@d710f85 with Intent { act=android.media.browse.MediaBrowserService cmp=pk.mohammadadnan.tunalapp/.MediaPlaybackService }: java.lang.NullPointerException: Attempt to invoke interface method 'android.os.IBinder androidx.media.MediaBrowserServiceCompat$MediaBrowserServiceImpl.onBind(android.content.Intent)' on a null object reference

我尝试将MediaBrowserServiceCompat更改为MediaBrowserService，崩溃的问题已解决，但未检测到媒体按钮。

MediaPlaybackService.class 

public class MediaPlaybackService extends MediaBrowserServiceCompat {


    //Not important for general audio service,required for class
    @Nullable
    @Override
    public BrowserRoot onGetRoot(@NonNull String clientPackageName,int clientUid,@Nullable Bundle rootHints) {
        if(TextUtils.equals(clientPackageName,getPackageName())) {
            return new BrowserRoot(getString(R.string.app_name),null);
        }

        return null;
    }

    @Override
    public void onLoadChildren(@NonNull String parentId,@NonNull Result<List<MediaBrowserCompat.MediaItem>> result) {
        result.sendResult(null);
    }


    private MediaSessionCompat mediaSessionCompat;
    private MediaSessionCompat.Callback mediaSessionCompatCallBack = new MediaSessionCompat.Callback()
    {
        @Override
        public void onPlay() {
            super.onPlay();
            Toast.makeText(getApplication(),"Play Button is pressed!",Toast.LENGTH_SHORT).show();
            mediaSessionCompat.setActive(true);
            setMediaPlaybackState(PlaybackStateCompat.STATE_PLAYING);
        }

        @Override
        public void onPause() {
            super.onPause();
            Toast.makeText(getApplication(),"Pause Button is pressed!",Toast.LENGTH_SHORT).show();
            setMediaPlaybackState(PlaybackStateCompat.STATE_PAUSED);
        }

        @Override
        public void onSkipToNext() {
            super.onSkipToNext();
            Toast.makeText(getApplication(),"Next Button is pressed!",Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onSkipToPrevious() {
            super.onSkipToPrevious();
            Toast.makeText(getApplication(),"Previous Button is pressed!",Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onStop() {
            super.onStop();
            Toast.makeText(getApplication(),"Stop Button is pressed!",Toast.LENGTH_SHORT).show();
        }

        @Override
        public boolean onMediaButtonEvent(Intent mediaButtonEvent) {
            String intentAction = mediaButtonEvent.getAction();

            if (Intent.ACTION_MEDIA_BUTTON.equals(intentAction))
            {
                KeyEvent event = mediaButtonEvent.getParcelableExtra(Intent.EXTRA_KEY_EVENT);

                if (event != null)
                {
                    int action = event.getAction();
                    if (action == KeyEvent.ACTION_DOWN) {
                        switch (event.getKeyCode()) {
                            case KeyEvent.KEYCODE_MEDIA_FAST_FORWARD:
                                // code for fast forward
                                return true;
                            case KeyEvent.KEYCODE_MEDIA_NEXT:
                                // code for next
                                return true;
                            case KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE:
                                // code for play/pause
                                Toast.makeText(getApplication(),Toast.LENGTH_SHORT).show();
                                return true;
                            case KeyEvent.KEYCODE_MEDIA_PREVIOUS:
                                // code for previous
                                return true;
                            case KeyEvent.KEYCODE_MEDIA_REWIND:
                                // code for rewind
                                return true;
                            case KeyEvent.KEYCODE_MEDIA_STOP:
                                // code for stop
                                Toast.makeText(getApplication(),Toast.LENGTH_SHORT).show();
                                return true;

                        }
                        return false;

                    }
                    if (action == KeyEvent.ACTION_UP) {

                    }
                }
            }
            return super.onMediaButtonEvent(mediaButtonEvent);
        }
    };




    @Override
    public void onCreate() {
        Toast.makeText(this,"My Service Created",Toast.LENGTH_LONG).show();
        Log.e("SERVICE","onCreate");

        initMediaSession();
        mediaSessionCompat.setActive(true);

    }

    @Override
    public void onDestroy() {
        Toast.makeText(this,"My Service Stopped","onDestroy");
        mediaSessionCompat.release();
    }

    @Override
    public int onStartCommand(Intent intent,int flags,int startId) {
        Toast.makeText(this,"My Service Started",Toast.LENGTH_LONG).show();
        Log.e("SERVICE_STARTUP","onStart");


        Intent intentTop = new Intent(Intent.ACTION_MEDIA_BUTTON);
        intentTop.setClass(this,MediaButtonReceiver.class);
        PendingIntent mbrIntent = PendingIntent.getBroadcast(this,intent,0);
        mediaSessionCompat.setMediaButtonReceiver(mbrIntent);

        MediaButtonReceiver.handleIntent(mediaSessionCompat,intent);
        return super.onStartCommand(intent,flags,startId);
    }


    private void initMediaSession() {
        ComponentName mediaButtonReceiver = new ComponentName(getApplicationContext(),MediaButtonReceiver.class);
        mediaSessionCompat = new MediaSessionCompat(getApplicationContext(),"Tag",mediaButtonReceiver,null);

        mediaSessionCompat.setCallback(mediaSessionCompatCallBack);
        mediaSessionCompat.setFlags( MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS | MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS );

        Intent mediaButtonIntent = new Intent(Intent.ACTION_MEDIA_BUTTON);
        mediaButtonIntent.setClass(this,MediaButtonReceiver.class);
        PendingIntent pendingIntent = PendingIntent.getBroadcast(this,mediaButtonIntent,0);
        mediaSessionCompat.setMediaButtonReceiver(pendingIntent);

        //setSessionToken(mediaSessionCompat.getSessionToken());
    }

    private void setMediaPlaybackState(int state) {
        PlaybackStateCompat.Builder playbackstateBuilder = new PlaybackStateCompat.Builder();
        if( state == PlaybackStateCompat.STATE_PLAYING ) {
            playbackstateBuilder.setActions(PlaybackStateCompat.ACTION_PLAY_PAUSE | PlaybackStateCompat.ACTION_PAUSE);
        } else {
            playbackstateBuilder.setActions(PlaybackStateCompat.ACTION_PLAY_PAUSE | PlaybackStateCompat.ACTION_PLAY);
        }
        playbackstateBuilder.setState(state,PlaybackStateCompat.PLAYBACK_POSITION_UNKNOWN,0);
        mediaSessionCompat.setPlaybackState(playbackstateBuilder.build());
    }
}

MainActivity.class 

public class MainActivity extends AppCompatActivity {

    private static final int STATE_PAUSED = 0;
    private static final int STATE_PLAYING = 1;

    private int mCurrentState;

    private MediaBrowserCompat mMediaBrowserCompat;
    private MediaControllerCompat mMediaControllerCompat;

    private Button mPlayPauseToggleButton;

    private MediaBrowserCompat.ConnectionCallback mMediaBrowserCompatConnectionCallback = new MediaBrowserCompat.ConnectionCallback() {

        @Override
        public void onConnected() {
            super.onConnected();
            try {
                mMediaControllerCompat = new MediaControllerCompat(MainActivity.this,mMediaBrowserCompat.getSessionToken());
                mMediaControllerCompat.registerCallback(mMediaControllerCompatCallback);
                MediaControllerCompat.setMediaController(MainActivity.this,mMediaControllerCompat);
                MediaControllerCompat.getMediaController(MainActivity.this).getTransportControls().playFromMediaId(String.valueOf(R.raw.warner_tautz_off_broadway),null);

            } catch( RemoteException e ) {

            }
        }
    };

    private MediaControllerCompat.Callback mMediaControllerCompatCallback = new MediaControllerCompat.Callback() {

        @Override
        public void onPlaybackStateChanged(PlaybackStateCompat state) {
            super.onPlaybackStateChanged(state);
            if( state == null ) {
                return;
            }

            switch( state.getState() ) {
                case PlaybackStateCompat.STATE_PLAYING: {
                    mCurrentState = STATE_PLAYING;
                    break;
                }
                case PlaybackStateCompat.STATE_PAUSED: {
                    mCurrentState = STATE_PAUSED;
                    break;
                }
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mPlayPauseToggleButton = (Button) findViewById(R.id.button);

        mMediaBrowserCompat = new MediaBrowserCompat(this,new ComponentName(this,MediaPlaybackService.class),mMediaBrowserCompatConnectionCallback,getIntent().getExtras());

        mMediaBrowserCompat.connect();

        mPlayPauseToggleButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if( mCurrentState == STATE_PAUSED ) {
                    MediaControllerCompat.getMediaController(MainActivity.this).getTransportControls().play();
                    mCurrentState = STATE_PLAYING;
                } else {
                    if( MediaControllerCompat.getMediaController(MainActivity.this).getPlaybackState().getState() == PlaybackStateCompat.STATE_PLAYING ) {
                        MediaControllerCompat.getMediaController(MainActivity.this).getTransportControls().pause();
                    }

                    mCurrentState = STATE_PAUSED;
                }
            }
        });

    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if( MediaControllerCompat.getMediaController(MainActivity.this).getPlaybackState().getState() == PlaybackStateCompat.STATE_PLAYING ) {
            MediaControllerCompat.getMediaController(MainActivity.this).getTransportControls().pause();
        }

        mMediaBrowserCompat.disconnect();
    }
}

Manifest.xml 

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="pk.mohammadadnan.tunalapp">

    <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
    <uses-feature android:name="android.hardware.bluetooth" />
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
    <uses-permission android:name="android.permission.BLUETOOTH" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

    <application
        android:allowBackup="false"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>

        </activity>
        <receiver android:name="androidx.media.session.MediaButtonReceiver"  >
            <intent-filter>
                <action android:name="android.intent.action.MEDIA_BUTTON" />
                <action android:name="android.media.AUDIO_BECOMING_NOISY" />
            </intent-filter>
        </receiver>
        <service android:name="pk.mohammadadnan.tunalapp.MediaPlaybackService"
            android:exported="false">
            <intent-filter>
                <action android:name="android.intent.action.MEDIA_BUTTON" />
                <action android:name="android.media.browse.MediaBrowserService" />
                <action android:name="android.media.AUDIO_BECOMING_NOISY" />
            </intent-filter>
        </service>
    </application>

</manifest>

解决方法

暂无找到可以解决该程序问题的有效方法，小编努力寻找整理中！

如果你已经找到好的解决方法，欢迎将解决方案带上本链接一起发送给小编。

小编邮箱:dio#foxmail.com (将#修改为@）

android-bluetoothandroid-intentandroid-mediasessionmediabrowserservicecompatservice

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