屏幕关闭时，前台服务上的 Android 蓝牙 LE 扫描仪立即停止

Question

我有以下 BLE 前台服务实现 -

public class BluetoothForegroundService extends Service {

    private PowerManager.WakeLock wakeLock;

    @Override
    public void onCreate() {
        super.onCreate();
        PowerManager powerManager = (PowerManager) getSystemService(Context.POWER_SERVICE);
        wakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK , this.getClass().getSimpleName());
        wakeLock.acquire();
    }


    @Override
    public void onDestroy() {
        super.onDestroy();
        wakeLock.release();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        super.onStartCommand(intent, flags, startId);
        Intent notificationIntent = new Intent(this, MainActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0);

        Notification notification = new NotificationCompat.Builder(this, "BLE test")
                .setContentTitle("Bluetooth Service")
                .setContentText("Fetching Bluetooth")
                .setSmallIcon(R.drawable.ic_launcher)
                .setContentIntent(pendingIntent)
                .build();

        startForeground(1, notification);

        BluetoothScanner bluetoothScanner = BluetoothScanner.getInstance(new BluetoothScanner.OnBlePacketBuilderListener() {
            @Override
            public void onBleObjectsCreated(BleBeaconPacketData beaconPacketData, BleHardwarePacketData bleBroadcastPacketData) {
                if (bleBroadcastPacketData == null && beaconPacketData == null) return;
                Log.d("onBleObjectsCreated", "onBleObjectsCreated");
                Intent intent = new Intent("action");
                if (beaconPacketData != null)
                    intent.putExtra("BleBeaconPacketData", beaconPacketData);
                if (bleBroadcastPacketData != null)
                    intent.putExtra("BleHardwarePacketData", bleBroadcastPacketData);
                sendBroadcast(intent);
            }
        });
        bluetoothScanner.startBluetooth();

        return START_STICKY;
    }

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

public class BluetoothScanner implements BluetoothAdapter.LeScanCallback, BlePacketBuilder.BlePacketBuilderListener {

    interface OnBlePacketBuilderListener{
        void onBleObjectsCreated(BleBeaconPacketData beaconPacketData, BleHardwarePacketData bleBroadcastPacketData);
    }

    private final OnBlePacketBuilderListener listener;
    private BluetoothAdapter bluetoothAdapter;
    public static BluetoothScanner instance;

    private BluetoothScanner(OnBlePacketBuilderListener listener) {
        this.listener = listener;
    }

    public static BluetoothScanner getInstance(OnBlePacketBuilderListener listener) {
        if (instance == null)
            instance = new BluetoothScanner(listener);
        return instance;
    }

    public void startBluetooth() {
        BluetoothManager bluetoothManager = MainApplication.getPureTrackApplicationContext().getSystemService(BluetoothManager.class);
        if ((bluetoothManager != null ? bluetoothManager.getAdapter() : null) == null) return;
        bluetoothAdapter = bluetoothManager.getAdapter();
        bluetoothAdapter.startLeScan(this);
    }

    public void stopBluetooth() {
        if (bluetoothAdapter == null) return;
        bluetoothAdapter.stopLeScan(this);
    }

    @Override
    public void onLeScan(BluetoothDevice bluetoothDevice, int rssi, byte[] scanRecord) {
        Log.d("BluetoothScanner", "New BLE - " + Arrays.toString(scanRecord));
        BlePacketBuilder blePacketBuilder = new BlePacketBuilder(this);
        blePacketBuilder.parseResult(bluetoothDevice, rssi, scanRecord);
    }


    @Override
    public void onfinishedToParseResults(BleBeaconPacketData beaconPacketData, BleHardwarePacketData bleBroadcastPacketData) {
        listener.onBleObjectsCreated(beaconPacketData, bleBroadcastPacketData);
    }
}

在我的 MainActivity 上，我正在接收广播 -

private void getBluetoothDataFromForegroundService() {
        registerReceiver(new BluetoothScannerReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                if (powerManager == null) return;
                Log.d("onReceiveBle", "onReceiveBle");

                //At this point data is handled both for UI and for network calls 
            }
        }, new IntentFilter("action"));
    }

问题是即使屏幕永远关闭，我也需要 BLE 来保持采样数据。这是一个内部产品，所以我不关心电池消耗或普通应用程序用户会担心的任何事情。我只需要永远对 BLE 进行采样，并通过网络调用相应地处理数据。

我尝试使用 WakeLock，但没有帮助。屏幕关闭时我没有获取日志，当屏幕重新打开时我没有获取日志。我缺少什么让 BLE 继续采样？

Answer 1

我认为你缺少一些东西。

Android 10 权限
在 Android 10 上，您通常必须获得 ACCESS_BACKGROUND_LOCATION 才能在您的应用不可见时进行信标检测。但是，如果您将 android:foregroundServiceType="location" 添加到清单中的前台服务声明中，则可以仅在授予前台位置权限和前台服务的情况下进行扫描。详情请看这里。

所以您需要ACCESS_BACKGROUND_LOCATION才能在A10+屏幕关闭时获得扫描结果。

另外，在A8中已经引入，（可以看here），扫描功能停止前有10分钟的限制。因此，我建议您使用 JobScheduler 或 Runnable 来制作 9 分钟计时器（或 10 分钟）并重置扫描。这样您就可以获得长时间的扫描服务。这是一个例子：

 mHandlerUpdate?.removeCallbacksAndMessages(null)

        mHandlerUpdate?.postDelayed(object : Runnable {
            override fun run() {
                Log.d(BleService::class.java.simpleName, "run: in runnable handler")
                scanner.stopScan(mScanCallback)

                scanner.startScan(
                    filters,
                    settings,
                    mScanCallback
                )
                mHandlerUpdate?.postDelayed(this, 60000)
            }
        }, 60000)

上面的处理程序每​​ 60 秒重置一次扫描。只是一个演示代码。您可以根据自己的需要进行修改。完成后记得removeCallbacksAndMessages。

此外，必须启用定位服务才能获得结果。你可以看到为什么here。

其他一些兴趣链接..

Chet talk

Develpers Android Bt Page