Android Bluetooth Discovery not working

Question

I am trying to list bluetooth devices available periodically. The idea is to run the startDiscovery() fuction every 4 secs and list the visible devices.

package com.neondude.cupid;

import android.app.Activity;
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.os.Bundle;
import android.os.Handler;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.Timer;
import java.util.TimerTask;

public class MainActivity extends Activity {

   Timer mTimer;
   private ListView listView;
   private ArrayList<String> mDeviceList = new ArrayList<String>();
   private BluetoothAdapter mBluetoothAdapter;
   private ArrayAdapter<String> BTArrayAdapter;
   Handler mHandler = new Handler();

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

       listView = (ListView) findViewById(R.id.listView);
       BTArrayAdapter = new ArrayAdapter<String>(this,R.layout.list_view);
       listView.setAdapter(BTArrayAdapter);

       mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

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

   private void startTimer(){
       mTimer = new Timer();
       mTimer.scheduleAtFixedRate(new Mytask(), 4000, 1000 * 5);
   }

   class Mytask extends TimerTask {
       @Override
       public void run(){
           mHandler.post(new Runnable(){
               @Override
               public void run(){

                   find();

               }
           });
       }
   }

   public void find(){

       if (mBluetoothAdapter.isDiscovering()) {
           mBluetoothAdapter.cancelDiscovery();
       }
       else {
           BTArrayAdapter.clear();
           mBluetoothAdapter.startDiscovery();

           registerReceiver(mReceiver, new IntentFilter(BluetoothDevice.ACTION_FOUND));
       }
       mBluetoothAdapter.startDiscovery();

   }

   final BroadcastReceiver mReceiver = 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);
               short rssi = intent.getShortExtra(BluetoothDevice.EXTRA_RSSI,Short.MIN_VALUE);

               BTArrayAdapter.add(device.getName() + "\n" + device.getAddress() + "\n" + rssi);
               BTArrayAdapter.notifyDataSetChanged();

           }
       }
   };

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



}

I have included the startDiscovery() function in the timertask handler. But when i do this , the devices and not listed in my listView.

Answer 1

You should check if the bluetooth is on, and ask the user to turn on if is off:

if (!mBluetoothAdapter.isEnabled()) {
    Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
    startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
}
else{

    startTimer();

}

You could start the timer onActivityResult()

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    // Check which request we're responding to
        if (resultCode == RESULT_OK) {
            // The user turn on the bluetooth
            startTimer();
        }
    }
}

Answer 2

从不调用startTimer()函数，因此timerTask不开始。