Android 蓝牙发现无法正常工作

我是android新手。 我正在尝试一个简单的android应用程序，它将： -用户单击按钮以启用BT -用户点击按钮，它将扫描附近的设备，并给出一个列表或尝试连接到特定的设备（应用程序将用于机器人） anble按钮工作正常并启用蓝牙功能，但当我按下扫描按钮时，它会启动discover，但没有返回任何回调。我已经设置了一个监听器，并将一些日志放在那里，但我没有从监听器中看到任何东西（我确信在测试时周围有可发现的设备） 代码如下：

    public class MainActivity extends AppCompatActivity {

        private BluetoothAdapter BA;
        private Set<BluetoothDevice> scannedDevices;
        private final static int REQUEST_ENABLE_BT = 1;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
            setSupportActionBar(toolbar);

            FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
            fab.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                            .setAction("Action", null).show();
                }
            });
            IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
            registerReceiver(mReceiver, filter);
        }

        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.menu_main, menu);
            return true;
        }

        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            // Handle action bar item clicks here. The action bar will
            // automatically handle clicks on the Home/Up button, so long
            // as you specify a parent activity in AndroidManifest.xml.
            int id = item.getItemId();

            //noinspection SimplifiableIfStatement
            if (id == R.id.action_settings) {
                return true;
            }

            return super.onOptionsItemSelected(item);
        }

        @Override
        protected void onDestroy() {
            super.onDestroy();
            BA.cancelDiscovery();
            // Don't forget to unregister the ACTION_FOUND receiver.
            unregisterReceiver(mReceiver);
        }


        private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
            public void onReceive(Context context, Intent intent)
            {
                Log.i("NKNKNK","onReceive method");
                String action = intent.getAction();
                if (BluetoothDevice.ACTION_FOUND.equals(action)) {
                    // A Bluetooth device was found
                    // Getting device information from the intent
                    BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                    Log.i("NKNKNK","Device found: " + device.getName() + "; MAC " + device.getAddress());
                }
            }
        };

        public void TunrONOnClick(View v)
        {
            // do something when the button is clicked
            Log.i("NKNKNK","TunrON button clicked");
            TextView output = findViewById(R.id.textView);

            BA = BluetoothAdapter.getDefaultAdapter();
            if (BA == null)
            {
                Log.i("NKNKNK","No BT device supported");
                return;
            }
            if (!BA.isEnabled()) {
                // We need to enable the Bluetooth, so we ask the user
                Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                // REQUEST_ENABLE_BT es un valor entero que vale 1
                startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
            }
            output.setText(BA.getName());
        }

        public void ScanOnClick(View v)
        {
            Log.i("NKNKNK","SCAN button clicked");

            BA = BluetoothAdapter.getDefaultAdapter();
            if (BA.isEnabled())
            {
                if (BA.isDiscovering()) {
                    BA.cancelDiscovery();
                }
                Log.i("NKNKNK","Starting discovery logged");
                BA.startDiscovery();
            }
        }
    }

编辑：我正在使用redmi note 4运行应用程序

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谢谢，嗨，我找到了解决我问题的方法，看来从安卓6开始，你必须申请许可，而不仅仅是在清单中声明它们。因此，在启用BT之前，我必须添加以下行：

    if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.ACCESS_COARSE_LOCATION)
            != PackageManager.PERMISSION_GRANTED) {
        Log.i("NKNKNK","Permission is not granted");
        ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.ACCESS_COARSE_LOCATION}, MY_PERMISSIONS_REQUEST_READ_CONTACTS);
    }

---

那么我的权限、请求、阅读、联系人是什么？

    if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.ACCESS_COARSE_LOCATION)
            != PackageManager.PERMISSION_GRANTED) {
        Log.i("NKNKNK","Permission is not granted");
        ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.ACCESS_COARSE_LOCATION}, MY_PERMISSIONS_REQUEST_READ_CONTACTS);
    }