Android上的蓝牙：StartDiscovery不起作用。无法扫描设备

Question

  bt.setOnClickListener(new OnClickListener() {
           @Override
           public void onClick(View v) {
               if (!(bluetooth.isEnabled())) {
                   status = "Bluetooth is not Enabled.";
                   Toast.makeText(AddUser.this, status, Toast.LENGTH_LONG).show();
                   Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                startActivityForResult(enableBtIntent, 1);

                }
                else
                {

                    scand();
                }

           }

 protected void onActivityResult(int requestCode, int resultCode, Intent intent) {
    System.out.println(resultCode);
    if (resultCode ==  RESULT_CANCELED) {
        status="Error Enabling bluetooth";
        Toast.makeText(AddUser.this, status, Toast.LENGTH_LONG).show();
    } else {

            scand();
    }



}

    private void scand()
{



   bluetooth.startDiscovery(); 
   Log.d("itmes", ""+items.size());
   item1 = new String[items.size()];
   item1 = items.toArray(item1);
   AlertDialog.Builder builder = new AlertDialog.Builder(this);
   builder.setTitle("Choose a device");
   builder.setItems(item1, new DialogInterface.OnClickListener() {

       public void onClick(DialogInterface dialog, int item) {
            Toast.makeText(getApplicationContext(), item1[item], Toast.LENGTH_SHORT).show();

       }

    });

    AlertDialog alert = builder.create();

    alert.show();

}

 private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();

            if (BluetoothDevice.ACTION_FOUND.equals(action)) 
            {
                   Log.e("br", "--- device found ---");
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);

               items.add(device.getName());
            }
          }
        };

filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
   registerReceiver(mReceiver, filter);

我已经在androidmanifest文件中设置了蓝牙权限。在上面的scand函数中，它应该显示已发现设备的列表，但它显示的是一个空对话框，只有标题。请告诉我如何正确使用startdiscovery和broadcastreceiver在AlertDialog中显示结果。

Answer 1

检查一下你有没有

 <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

在你的舱单上。

参见https://developer.android.com/reference/android/bluetooth/bluetoothdevice#action_found