Android蓝牙API找不到任何设备

Question

我正在尝试在我的应用程序中实现蓝牙设备发现功能。我已经实现了使用BluetoothAdapter和BroadcastReceiver这样做的建议方法：

My Activity (discover() is called in onCreate):

    public class MapsActivity extends AppCompatActivity implements OnMapReadyCallback {
        BluetoothAdapter mBluetoothAdapter;
        private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
            public void onReceive(Context context, Intent intent) {
                String action = intent.getAction();

                //Finding devices
                if (BluetoothAdapter.ACTION_DISCOVERY_STARTED.equals(action)) {
                    //discovery starts, we can show progress dialog or perform other tasks
                    testDevice("Start discover");
                } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
                    //discovery finishes, dismis progress dialog
                    testDevice("Discovery finished");
                } else if (BluetoothDevice.ACTION_FOUND.equals(action)) {
                    //bluetooth device found
                    BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                    testDevice("Found device " + device.getName());
                }
            }
        };

        public void discover() {
            this.mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

            IntentFilter filter = new IntentFilter();

            filter.addAction(BluetoothDevice.ACTION_FOUND);
            filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_STARTED);
            filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
            registerReceiver(mReceiver, filter);
            mBluetoothAdapter.startDiscovery();
        }

        public void testDevice(String msg) {
                Toast.makeText(this, msg,
                        Toast.LENGTH_LONG).show();
        }

}

在我的清单中，我有以下权限：

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

结果是我得到两个祝酒词：“开始发现”，10秒后“发现完成”。从未找到过设备。我已经测试了三星S9 +，Sansumg Tab A和摩托罗拉的东西（蓝牙开启）。

有什么我不做的事还是有任何我不知道的已知问题？

Answer 1

我的结论是纯粹的猜测，但是如果你在API级别23 +上运行（可能你是），你需要动态地请求权限，而不仅仅是在清单中声明它们。要么使用RxPermissions，要么使用ContextCompat.checkSelfPermission。