通过蓝牙扫描未检测到蓝牙设备

Question

我制作了一个android应用程序来扫描蓝牙设备，并向我的服务器发送一个HTTP请求，这样我就可以检测它们是开着还是关着。我已经用我的带有蓝牙适配器的台式电脑测试过了，效果很好。当检测到电脑上的蓝牙功能时，它显示电脑是打开的，当我关闭电脑上的蓝牙功能时，它是关闭的。现在，我需要使用这个应用程序的设备有：雅伯投影仪、Bose SoundLink和JBL耳机，但我遇到了一些问题。

首先，投影仪似乎无法与手机通信，我只能连接耳机或扬声器进入投影仪BT设置并扫描设备，但当我扫描手机时，什么都没有出现，比如投影仪对手机不可见，导致应用程序检测到它总是关闭。如果我用手机扫描投影仪也是一样。这怎么可能？

最后是扬声器和耳机，似乎一旦它们连接到设备（例如投影仪），它们就不再对手机可见，我认为这与节省电池/安全有关。但是有没有一种变通方法可以在连接时仍然能够检测到它们？

谢谢

编辑

这是服务中运行扫描的代码，据我所知，它使用的是蓝牙分类技术。

    private BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
private ArrayList<BluetoothDevice> arrayList = new ArrayList<>();

    @Override
public int onStartCommand(Intent intent, int flags, int startId) {

    createNotificationChannel();

    Intent intent1 = new Intent(this, MainActivity.class);
    PendingIntent pendingIntent = PendingIntent.getActivity(this,0,intent1,0);

    Notification notification = new NotificationCompat.Builder(this,"BTAPP")
            .setContentTitle("Bluetooth Scan")
            .setContentText("App is scanning")
            .setContentIntent(pendingIntent).build();

    startForeground(1,notification);

    IntentFilter intentFilter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
    IntentFilter intentFilter2 = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_STARTED);
    IntentFilter intentFilter3 = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
    registerReceiver(broadcastReceiver, intentFilter);
    registerReceiver(broadcastReceiver, intentFilter2);
    registerReceiver(broadcastReceiver, intentFilter3);
    bluetoothAdapter.startDiscovery();

    return START_STICKY;
}

final BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {

    @RequiresApi(api = Build.VERSION_CODES.O)
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();

        // When discovery starts
        if (BluetoothAdapter.ACTION_DISCOVERY_STARTED.equals(action)) {
            //clearing any existing list data
            flagJBL = false;
            flagBose = false;
            flagProjector = false;
            arrayList.clear();
        }

        // When discovery finds a device
        if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            // Get the BluetoothDevice object from the Intent
            BluetoothDevice device =
                    intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);

            // Add the name and address to an array adapter
            if (!arrayList.contains(device)) {
                if (device.getAddress().equals(JBL_HEADSET_ADDRESS))
                    flagJBL = true;
                if (device.getAddress().equals(BOSE_SOUNDLINK_ADDRESS))
                    flagBose = true;
                if (device.getAddress().equals(PROJECTOR_ADDRESS))
                    flagProjector = true;
                arrayList.add(device);
            }
        }

        // When discovery starts
        if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
            //clearing any existing list data
            //Toast.makeText(getApplicationContext(), "Scan has stopped",Toast.LENGTH_SHORT).show();
            if (flagJBL) {
                Intent jbloni = new Intent(getApplicationContext(), RequestHandler.class);
                jbloni.putExtra("URL",JBL_ON_URL);
                startService(jbloni);
            }
            //showNotification("JBL Result", "JBL is On");
            else {
                Intent jbloffi = new Intent(getApplicationContext(), RequestHandler.class);
                jbloffi.putExtra("URL",JBL_OFF_URL);
                startService(jbloffi);
            }
            //showNotification("JBL Result", "JBL is Off");
            if (flagBose) {
                Intent boseoni = new Intent(getApplicationContext(), RequestHandler.class);
                boseoni.putExtra("URL",BOSE_ON_URL);
                startService(boseoni);
                // showNotification("Bose Result", "Bose is On");
            }
            else {
                Intent boseoffi = new Intent(getApplicationContext(), RequestHandler.class);
                boseoffi.putExtra("URL",BOSE_OFF_URL);
                startService(boseoffi);
                //showNotification("Bose Result", "Bose is Off");
            }
            if (flagProjector) {
                Intent projectoroni = new Intent(getApplicationContext(), RequestHandler.class);
                projectoroni.putExtra("URL",PROJECTOR_ON_URL);
                startService(projectoroni);
                //showNotification("Projector Result", "Projector is On");
            }
            else {
                Intent projectoroffi = new Intent(getApplicationContext(), RequestHandler.class);
                projectoroffi.putExtra("URL",PROJECTOR_OFF_URL);
                startService(projectoroffi);
                //showNotification("Projector Result", "Projector is Off");
            }

            bluetoothAdapter.startDiscovery();
        }
    }
};

Answer 1

根据你的描述，你的Android应用程序似乎只扫描蓝牙LE设备。由于投影仪很可能使用Bluetooth classic，除名称外，这两种技术都不兼容，因此无法扫描。如果你也想检测这些设备，你需要在第二步扫描蓝牙经典设备。

就您的扬声器和耳机而言，根据我的观察，我可以说这种行为实际上是行业标准的。即使在技术上可以在连接期间继续宣传一个人的存在，从应用程序的角度来看，它只在极少数情况下才有意义，因此很少实施。