即使附近的蓝牙设备已开启，也无法发现设备

Question

我创建了一个用于蓝牙准备的活动，并为蓝牙功能嵌入了一个片段。 所有必需的权限，如精细位置和粗略位置都添加到androidmanifest文件。这里没有添加xml文件，因为没有占用太多空间。发现开始后我查看了日志，但没有看到日志中的附近设备。我不知道出了什么问题。

MyActivity.java

public class MainActivity extends AppCompatActivity{
BluetoothAdapter bluetoothAdapter = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
    if (bluetoothAdapter == null) {
        new AlertDialog.Builder(this)
                .setTitle("Not Compatible")
                .setMessage("Your phone does not support Bluetooth")
                .setPositiveButton("Exit", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        System.exit(0);
                    }
                }).show();
    }
    if (!bluetoothAdapter.isEnabled()) {
        Intent enableBluetooth = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        startActivityForResult(enableBluetooth, 1);
    }

    ScanFragment scanFragment = ScanFragment.newInstance(bluetoothAdapter);
    getSupportFragmentManager().beginTransaction().add(R.id.frame_container, scanFragment).commit();
}

ScanFragment

public class ScanFragment extends android.support.v4.app.Fragment implements View.OnClickListener {

private List<DeviceItem> deviceItems;
private Set<BluetoothDevice> bondedDevices;
private List<BroadcastReceiver> receivers;
private static BluetoothAdapter bluetoothAdapter;
private Button scanButton;
private ArrayAdapter<DeviceItem> mAdapter;

public static ScanFragment newInstance(BluetoothAdapter bluetoothAdapter) {
    ScanFragment fragment = new ScanFragment();
    ScanFragment.bluetoothAdapter = bluetoothAdapter;
    return fragment;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    deviceItems = new ArrayList<>();
    receivers = new ArrayList<>();
    bondedDevices = bluetoothAdapter.getBondedDevices();
    mAdapter = new ArrayAdapter<DeviceItem>(this.getContext(), android.R.layout.simple_list_item_1, android.R.id.text1);
    if (bondedDevices.size() > 0) {
        System.out.println("ScanFragment " + "pairded devices are below");
        for (BluetoothDevice device : bondedDevices) {
            DeviceItem newDevice = new DeviceItem(device.getName(), device.getAddress(), "false");
            deviceItems.add(newDevice);
            System.out.println("ScanFragment pairded deviceName" + newDevice.getDeviceName());
            System.out.println("ScanFragment pairded deviceAddress " + newDevice.getAddress());
        }
    }
}
@Override
public View onCreateView(LayoutInflater layoutInflater, ViewGroup viewGroup, Bundle savedInstanceState) {
    View view = layoutInflater.inflate(R.layout.scan_fragment, viewGroup, false);
    scanButton = (Button) view.findViewById(R.id.button_scan);
    scanButton.setOnClickListener(this);
    return view;
}


@Override
public void onClick(View v) {
    if (v == scanButton) {
        if (bluetoothAdapter.isDiscovering()) {
            bluetoothAdapter.cancelDiscovery();
        }
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(BluetoothAdapter.ACTION_DISCOVERY_STARTED);
        intentFilter.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
        intentFilter.addAction(BluetoothDevice.ACTION_FOUND);
        getActivity().registerReceiver(broadcastReceiver, intentFilter);
        receivers.add(broadcastReceiver);
        checkBluetoothPermission();
        bluetoothAdapter.startDiscovery();
    }
}

private final BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        switch (action) {
            case BluetoothAdapter.ACTION_DISCOVERY_STARTED:
                System.out.println("ScanFragment " + "scan started");
                break;
            case BluetoothAdapter.ACTION_DISCOVERY_FINISHED:
                System.out.println("ScanFragment " + "scan finished");
                break;
            case BluetoothDevice.ACTION_FOUND:
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                DeviceItem newDevice = new DeviceItem(device.getName(), device.getAddress(), "false");
                System.out.println("ScanFragment " + "device found " + device.getName());
                mAdapter.add(newDevice);
                break;
        }
    }
};

@Override
public void onDestroy() {
    super.onDestroy();
    if (receivers.contains(broadcastReceiver)) {
        getActivity().unregisterReceiver(broadcastReceiver);
    }
    if (bluetoothAdapter.isDiscovering()) {
        bluetoothAdapter.cancelDiscovery();
        System.out.println("ScanFragment " + "device discovery cancelled");
    }
}

private void checkBluetoothPermission() {
    if (Build.VERSION.SDK_INT > Build.VERSION_CODES.LOLLIPOP) {
        int permission_check = getActivity().checkSelfPermission("Manifest.permission.ACCESS_FINE_LOCAITON");
        permission_check += getActivity().checkSelfPermission("Manifest.permission.ACCESS_COARSE_LOCATION");
        if (permission_check != 0) {
            getActivity().requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION}, 1001);
        }
    }
}

DeviceItem

public class DeviceItem {
private String deviceName;
private String address;
private boolean connected;

public String getDeviceName() {
    return deviceName;
}

public boolean getConnected() {
    return connected;
}

public String getAddress() {
    return address;
}

public void setDeviceName(String deviceName) {
    this.deviceName = deviceName;
}

public DeviceItem(String name, String address, String connected){
    this.deviceName = name;
    this.address = address;
    if (connected == "true") {
        this.connected = true;
    }
    else {
        this.connected = false;
    }
}