MediaBrowserServiceCompat 无法绑定到服务 [英] MediaBrowserServiceCompat unable to bind to service

问题描述

我的代码非常简单，我只想使用 MediaBrowserServiceCompat 绑定到音乐服务，实际上我有一个更大的程序，但存在同样的问题，所以我尝试制作一个没有所有不重要部分的更小程序，但出现以下错误:

My code is very simple, i just want to bind to the music service using MediaBrowserServiceCompat, actually i have a bigger program with the same problem so i tried to make a smaller one without all the unimportant parts and i get the following error:

08-27 11:31:30.848 12214-12214/com.example.android.newcheck E/AndroidRuntime:致命异常:主要进程:com.example.android.newcheck，PID:12214java.lang.RuntimeException: 无法使用 Intent { act=android.media.browse.MediaBrowserService cmp=com.example.android.newcheck/.MusicStreamService } 绑定到服务 com.example.android.newcheck.MusicStreamService@8c043ff:java.lang.NullPointerException:尝试在空对象引用上调用接口方法android.os.IBinder android.support.v4.media.MediaBrowserServiceCompat$MediaBrowserServiceImpl.onBind(android.content.Intent)"在 android.app.ActivityThread.handleBindService(ActivityThread.java:3847)在 android.app.ActivityThread.access$2200(ActivityThread.java:221)在 android.app.ActivityThread$H.handleMessage(ActivityThread.java:1887)在 android.os.Handler.dispatchMessage(Handler.java:102)在 android.os.Looper.loop(Looper.java:158)在 android.app.ActivityThread.main(ActivityThread.java:7224)在 java.lang.reflect.Method.invoke(Native Method)在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)引起:java.lang.NullPointerException:尝试在空对象引用上调用接口方法'android.os.IBinder android.support.v4.media.MediaBrowserServiceCompat$MediaBrowserServiceImpl.onBind(android.content.Intent)'在 android.support.v4.media.MediaBrowserServiceCompat.onBind(MediaBrowserServiceCompat.java:613)在 android.app.ActivityThread.handleBindService(ActivityThread.java:3834)在 android.app.ActivityThread.access$2200(ActivityThread.java:221)在 android.app.ActivityThread$H.handleMessage(ActivityThread.java:1887)在 android.os.Handler.dispatchMessage(Handler.java:102)在 android.os.Looper.loop(Looper.java:158)在 android.app.ActivityThread.main(ActivityThread.java:7224)在 java.lang.reflect.Method.invoke(Native Method)在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)

08-27 11:31:30.848 12214-12214/com.example.android.newcheck E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.android.newcheck, PID: 12214 java.lang.RuntimeException: Unable to bind to service com.example.android.newcheck.MusicStreamService@8c043ff with Intent { act=android.media.browse.MediaBrowserService cmp=com.example.android.newcheck/.MusicStreamService }: java.lang.NullPointerException: Attempt to invoke interface method 'android.os.IBinder android.support.v4.media.MediaBrowserServiceCompat$MediaBrowserServiceImpl.onBind(android.content.Intent)' on a null object reference at android.app.ActivityThread.handleBindService(ActivityThread.java:3847) at android.app.ActivityThread.access$2200(ActivityThread.java:221) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1887) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:158) at android.app.ActivityThread.main(ActivityThread.java:7224) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120) Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'android.os.IBinder android.support.v4.media.MediaBrowserServiceCompat$MediaBrowserServiceImpl.onBind(android.content.Intent)' on a null object reference at android.support.v4.media.MediaBrowserServiceCompat.onBind(MediaBrowserServiceCompat.java:613) at android.app.ActivityThread.handleBindService(ActivityThread.java:3834) at android.app.ActivityThread.access$2200(ActivityThread.java:221)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1887)  at android.os.Handler.dispatchMessage(Handler.java:102)  at android.os.Looper.loop(Looper.java:158)  at android.app.ActivityThread.main(ActivityThread.java:7224)  at java.lang.reflect.Method.invoke(Native Method)  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120) 

我主要使用 youtube 上的 Ian Lake 讲座并做了他说的一切，但我不知道为什么会出现此错误，我尝试在网上寻找答案但找不到任何答案.谢谢您的帮助.

i mainly used Ian Lake lectures on youtube and did everything he said but i don't know why i get this error, i try to find answers online but couldn't find any answer. thanks for the help.

AndroidManifest:

AndroidManifest:

    <service
        android:name=".MusicStreamService"
        android:exported="true">
        <intent-filter>
            <action android:name="android.media.browse.MediaBrowserService" />
        </intent-filter>
    </service>

主要活动:

    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    MediaBrowserCompat mediaBrowser = new MediaBrowserCompat(MainActivity.this, new ComponentName(MainActivity.this, MusicStreamService.class),
            new MediaBrowserCompat.ConnectionCallback() {
                @Override
                public void onConnected() {
                    Log.v("MainActivity","connected");
                }
                @Override
                public void onConnectionSuspended() {
                    super.onConnectionSuspended();
                }
                @Override
                public void onConnectionFailed() {
                    super.onConnectionFailed();
                }
            }, null);
    mediaBrowser.connect();
    Button click = (Button) findViewById(R.id.button);
    click.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            startService(new Intent(MainActivity.this, MusicStreamService.class));
        }
    });
}

音乐流服务:

public class MusicStreamService extends MediaBrowserServiceCompat {
@Nullable
@Override
public BrowserRoot onGetRoot(@NonNull String clientPackageName, int clientUid, @Nullable Bundle rootHints) {
    Log.v("***********", "getroot");
    return new BrowserRoot(getString(R.string.app_name), // Name visible in Android Auto
            null); // Bundle of optional extras
}

@Override
public void onLoadChildren(@NonNull String parentId, @NonNull Result<List<MediaBrowserCompat.MediaItem>> result) {
    Log.v("*********", "one step before connect2");
    result.sendResult(null);
}

@Override
public void onCreate() {
    MediaSessionCompat mediaSession = new MediaSessionCompat(this, MusicStreamService.class.getSimpleName());
    setSessionToken(mediaSession.getSessionToken());
    mediaSession.setFlags(MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS |
            MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS);
    mediaSession.setActive(true);
}

推荐答案

我忘记在 MusicStreamService 类的 onCreate 方法中编写 super.onCreate().解决了.

I forgot to write super.onCreate() in the onCreate method in MusicStreamService class. solved.

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