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Here is my code

import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

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

            if (BluetoothDevice.ACTION_FOUND.equals(action)) {                
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                devices.add(device.getName());                
            } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
                mBtAdapter.startDiscovery();
                Toast.makeText(MainActivity.this,"Discovering "+devices.size(),Toast.LENGTH_SHORT).show();
                ArrayAdapter arrayAdapter=new ArrayAdapter(MainActivity.this,android.R.layout.simple_list_item_1,devices);
                listView.setAdapter(arrayAdapter);
                }
            }

    };

    ListView listView;
    ArrayList<String> devices;
    private BluetoothAdapter mBtAdapter;  

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

        listView=(ListView) findViewById(R.id.listView);
        devices=new ArrayList<String>();

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

        filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
        this.registerReceiver(mReceiver, filter);

        mBtAdapter = BluetoothAdapter.getDefaultAdapter();

        if(!mBtAdapter.isEnabled()){
            mBtAdapter.enable();
        }

        mBtAdapter.startDiscovery();        
    }

    @Override
    protected void onDestroy(){
        super.onDestroy();
        mBtAdapter.cancelDiscovery();
        unregisterReceiver(mReceiver);
    }
}

Problem is it always displays Discovering 0 as the size of devices arrayList is always 0. But phone detects the nearby available devices as in picture below Screenshot of phone bluetooth settings .I think my app broadcast receiver doesn't detect bluetooth devices available because there is an error in my code.Please help me

Sachith Senanayaka
  • 61
  • 7

1 Answers1

1

You don't have to register your receiver twice, intent filter can hold multiple actions.

IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(BluetoothDevice.ACTION_FOUND);
intentFilter.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
registerReceiver(yourReceiver, intentFilter);

Check that you have permissions that necessary for scanning:

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

Not all Bluetooth devices are discoverable in normal mode, please take a look on BluetoothLeScanner and startLeScan method of Bluetooth adapter:

BluetoothManager bluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE); 
BluetoothAdapter bluetoothAdapter = bluetoothManager.getAdapter();

bluetoothAdapter.getBluetoothLeScanner().startScan(yourCallback); // API 21+
bluetoothAdapter.startLeScan(yourCallback); // API 18+

Also it take some time to turn on the Bluetooth on the device, you should listen to Bluetooth state changes and start the discovery after its turned on and ready to use, take a look on this answer.

Alex Kamenkov
  • 891
  • 1
  • 6
  • 16