Check BlueTooth status during App Start and Monitor status using broad cast receiver

Manifest Permissions

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

Main activity

import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.ImageButton;
import android.widget.Toast;


public class MainActivity extends ActionBarActivity {
   
        private BluetoothAdapter mBluetoothAdapter = null;
     private static final int REQUEST_ENABLE_BT = 3;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
       
       
        mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

       //register BroadcastReceiver here
         registerReceiver(new BTStateChangedBroadcastReceiver(),
                    new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED));
              if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();
        }
       
                   
       
       
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.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();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

   
   
     @Override
        public void onStart() {
            super.onStart();
        

            // If BT is not on, request that it be enabled.
            // setupChat() will then be called during onActivityResult
            if (!mBluetoothAdapter.isEnabled()) {
                Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                startActivityForResult(enableIntent, REQUEST_ENABLE_BT);
            // Otherwise, setup the chat session
            }
        }
     public void onActivityResult(int requestCode, int resultCode, Intent data) {
           
            switch (requestCode) {
         
            case REQUEST_ENABLE_BT:
                // When the request to enable Bluetooth returns
                if (resultCode == Activity.RESULT_OK) {
                       Toast.makeText(this, R.string.bt_enabled, Toast.LENGTH_SHORT).show();
                
                } else {
                    // User did not enable Bluetooth or an error occurred
                    Toast.makeText(this, R.string.bt_not_enabled_leaving, Toast.LENGTH_SHORT).show();
                    finish();
                }
            }
        }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container,
                    false);
            return rootView;
        }
    }

}

BroadCast Receiver :

This is needed in order to monitor status

import android.bluetooth.BluetoothAdapter;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;

public class BTStateChangedBroadcastReceiver extends BroadcastReceiver {
   
     @Override
     public void onReceive(Context context, Intent intent) {
      int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE,
        -1);
      
      switch(state){
      case BluetoothAdapter.STATE_CONNECTED:
       Toast.makeText(context,
        "BTStateChangedBroadcastReceiver: STATE_CONNECTED",
        Toast.LENGTH_SHORT).show();
       break;
      case BluetoothAdapter.STATE_CONNECTING:
       Toast.makeText(context,
        "BTStateChangedBroadcastReceiver: STATE_CONNECTING",
        Toast.LENGTH_SHORT).show();
       break;
      case BluetoothAdapter.STATE_DISCONNECTED:
       Toast.makeText(context,
        "BTStateChangedBroadcastReceiver: STATE_DISCONNECTED",
        Toast.LENGTH_SHORT).show();
       break;
      case BluetoothAdapter.STATE_DISCONNECTING:
       Toast.makeText(context,
        "BTStateChangedBroadcastReceiver: STATE_DISCONNECTING",
        Toast.LENGTH_SHORT).show();
       break;
      case BluetoothAdapter.STATE_OFF:
       Toast.makeText(context,
        context.getResources().getString(R.string.bluetooth_alert),
        Toast.LENGTH_SHORT).show();
       break;
      case BluetoothAdapter.STATE_ON:
       Toast.makeText(context,
        "BTStateChangedBroadcastReceiver: STATE_ON",
        Toast.LENGTH_SHORT).show();
       break;
      case BluetoothAdapter.STATE_TURNING_OFF:
       Toast.makeText(context,
        "BTStateChangedBroadcastReceiver: STATE_TURNING_OFF",
        Toast.LENGTH_SHORT).show();
       break;
      case BluetoothAdapter.STATE_TURNING_ON:
       Toast.makeText(context,
        "BTStateChangedBroadcastReceiver: STATE_TURNING_ON",
        Toast.LENGTH_SHORT).show();
       break;
      }
     }
   
    }