发现蓝牙设备

Question

this code for search and discovering bluetooth devices
i make Toast on BroadcastReceiver they don't even show it (android 7 a guess the issue in permission i just put it on mainfist)

    Button button;
    ListView listView;
    BluetoothAdapter mBluetoothAdapter;
    Integer requestbluetooth=1;
    ArrayList<String> arrayList;
    ArrayAdapter<String> Adapter;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        arrayList =new ArrayList<>();
        button=findViewById(R.id.printButton);
        listView=findViewById(R.id.listView);

        Adapter = new ArrayAdapter<String>(getBaseContext(),android.R.layout.simple_list_item_1,arrayList);
        listView.setAdapter(Adapter);

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


        button.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View view) {
                mBluetoothAdapter.startDiscovery();
            }
        });
    }

        BroadcastReceiver receiver = new BroadcastReceiver() {
            public void onReceive(Context context, Intent intent) {
                String action = intent.getAction();
                if (BluetoothDevice.ACTION_FOUND.equals(action)) {
                    BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);

                        String deviceName = device.getName();
                        String deviceHardwareAddress = device.getAddress(); 
                        arrayList.add(deviceName);
                        Adapter.notifyDataSetChanged();
                }
            }
        };

Answer 1

Since Android 6.0 (API level 23) you have to request the permissions at runtime. Most application do that when the user is starting the app for the first time.

To check if you have the permission already, use

int permissionCheck = ContextCompat.checkSelfPermission(thisActivity, Manifest.permission.READ_SMS);

To request permission, use

ActivityCompat.requestPermissions(thisActivity, new String[]{Manifest.permission.READ_SMS}, MY_PERMISSIONS_REQUEST_READ_CONTACTS);