android监听耳机按键

app 在前台的监听方式：

@Override
boolean onKeyDown(int keyCode, KeyEvent event) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            return super.onKeyDown(keyCode, event);
        }
        switch (keyCode) {
            case KeyEvent.KEYCODE_MEDIA_PLAY:
                    //这个地方写处理事件
                    return true;
        }
        return super.onKeyDown(keyCode, event);
}

app 后台+前台 同时监听：

AndroidManifest.xml 文件：

1、添加 receiver
2、添加 service

<application>
    <receiver
        android:name=".MediaButtonReceiver"
        android:exported="true">
        <intent-filter>
            <action android:name="android.intent.action.MEDIA_BUTTON" />
        </intent-filter>
    </receiver>
    <service
        android:name=".BackgroundMusicService"
        android:exported="true"
        android:enabled="true"
    >
        <intent-filter >
            <action android:name="android.intent.action.MEDIA_BUTTON" />
        </intent-filter>
    </service>
</application>

MediaButtonReceiver.java 文件：

public class MediaButtonReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "receiver", Toast.LENGTH_SHORT).show();//应用是最后一个播放过音频的，则会被通知
        System.out.println("receive");
    }

}

BackgroundMusicService.java 文件：

---

注意：必须创建通知，否则应用会在五秒后报错闪退

---

public class BackgroundMusicService extends Service {
    // MediaPlayer player;
    Notification customNotification;

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        // player = MediaPlayer.create(this, R.raw.numb); // 注意，应用需要在启动时候播放一段音频来获取按钮事件通知的优先权
        // player.setLooping(false);
        // player.setVolume(100, 100);

        setNotification();
        startForeground(200, customNotification);
    }

    private static final String CHANNEL_ID = "channelID";
    private void setNotification() {
        RemoteViews rv = new RemoteViews(getPackageName(), R.layout.custom_notification);//通知布局样式
        customNotification = new NotificationCompat.Builder(this, CHANNEL_ID)
                .setSmallIcon(R.drawable.more)
                .setCustomContentView(rv)
                .build();
        NotificationChannel channel = null;
        NotificationManager notificationManager = (NotificationManager) this.getSystemService(NOTIFICATION_SERVICE);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            channel = new NotificationChannel(CHANNEL_ID, "channel_name", NotificationManager.IMPORTANCE_DEFAULT);
            notificationManager.createNotificationChannel(channel);
        }
    }

    public void stop(){
        // player.pause();
    }

    public void play(){
        // player.start();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Toast.makeText(this, "onStartCommand", Toast.LENGTH_SHORT).show();
        return Service.START_STICKY;
    }


    @Override
    public void onDestroy() {
        // player.stop();
        // player.release();
    }
}

MainActivity.java 文件：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    binding = ActivityMainBinding.inflate(getLayoutInflater());
    setContentView(binding.getRoot());
    setSupportActionBar(binding.toolbar);
    media();
}

// 这个地方需要注意ms必须为成员变量，不能是局部变量，否则在应用进入后台状态会被垃圾回收器回收掉
MediaSessionCompat ms;
PlaybackStateCompat ps;
private void media(){
    Intent svc = new Intent(this, BackgroundMusicService.class);
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        startService(svc);
    }
    ms = new MediaSessionCompat(this, "My__MediaSessionTag");
    ms.setActive(true);
    ms.setFlags(MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS | MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS);
    Intent mediaButtonIntent = new Intent(Intent.ACTION_MEDIA_BUTTON);
    mediaButtonIntent.setClass(this, MediaButtonReceiver.class);
    ms.setMediaButtonReceiver(PendingIntent.getBroadcast(this, 100, mediaButtonIntent, 0));
    ps = new PlaybackStateCompat.Builder().setActions(PlaybackStateCompat.ACTION_PLAY_PAUSE
                    | PlaybackStateCompat.ACTION_PLAY | PlaybackStateCompat.ACTION_PAUSE |
                    PlaybackStateCompat.ACTION_SKIP_TO_NEXT | PlaybackStateCompat.ACTION_SKIP_TO_PREVIOUS |
                    PlaybackStateCompat.ACTION_FAST_FORWARD | PlaybackStateCompat.ACTION_REWIND)
            .setState(PlaybackStateCompat.STATE_PAUSED, 0 /*PlaybackStateCompat.PLAYBACK_POSITION_UNKNOWN*/, 1f)
            .build();
    ms.setPlaybackState(ps);
    ms.setFlags(MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS);

    //应用在前台、后台（活动状态）会触发这里的事件
    ms.setCallback(new MediaSessionCompat.Callback() {
        @Override
        public void onCommand(@NonNull String command, @Nullable Bundle args, @Nullable ResultReceiver cb) {
            super.onCommand(command, args, cb);
            System.out.println("onCommand");
        }

        @Override
        public void onPlay() {
            super.onPlay();
            System.out.println("onPlay");
        }

        @Override
        public void onPause() {
            super.onPause();
            System.out.println("onPause");
        }

        @Override
        public void onStop() {
            super.onStop();
            System.out.println("onStop");
        }
    });
}

最后附图 耳机键按下后的流程图：