Android Activity Service Android

I am using android software which has service and activity. And I am doing some code according to youtube video. But when I click the Start button, the Start button works fine. But after I restarted the service (by clicking the Stop button and then clicking Start again) the program crashed. So can anyone please help me figure this out.

Also is there a way in android for two way communication between service and activity? (Example: - the service gets the GPS location and changes the position to 0.001 and after that the ui automatically displays the edited position)

Please SomeOne help me figure this out.

My code: -

MyActivity.java

package com.example.autocomplete.servicemessenger;

import android.app.Activity;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.os.Message;
import android.os.Messenger;
import android.os.RemoteException;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Toast;


public class MyActivity extends Activity {
    boolean status=false;
    Messenger msngr=null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);
    }


    @Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.my, 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);
}

public void startMethod(View v){
    if (status){
        Toast.makeText(getApplicationContext(), "already started", Toast.LENGTH_SHORT).show();
    }
    else {
        Intent i = new Intent(this, MyService.class);
        bindService(i, mConnection, Context.BIND_AUTO_CREATE);
        status = true;
        Toast.makeText(getApplicationContext(), "start", Toast.LENGTH_SHORT).show();
    }
}

public void stoptMethod(View v){
    if (status) {
        Intent i = new Intent(this, MyService.class);
        unbindService(mConnection);
        stopService(i);

        mConnection = null;
        status = false;
        Toast.makeText(getApplicationContext(), "stop", Toast.LENGTH_SHORT).show();
    }
    else{
        Toast.makeText(getApplicationContext(), "already stopped", Toast.LENGTH_SHORT).show();
    }
}

public void runMethod(View v){
    Message ms=Message.obtain(null,1,0,0,0);
    String s="This is the message by Activity";
    Bundle bn=new Bundle();
    bn.putString("my_string",s);
    ms.setData(bn);
    try {
        msngr.send(ms);
    } catch (RemoteException e) {
        e.printStackTrace();
    }

}

ServiceConnection mConnection=new ServiceConnection() {
    @Override
    public void onServiceConnected(ComponentName componentName, IBinder service) {
        msngr=new Messenger(service);
        status=true;
    }

    @Override
    public void onServiceDisconnected(ComponentName componentName) {
        msngr=null;
        status=false;
        Toast.makeText(getApplicationContext(),"Disc",Toast.LENGTH_SHORT).show();
    }
};
}

      

        
        
        
      

    

MyService.java

package com.example.autocomplete.servicemessenger;

import android.app.Service;
import android.content.Intent;
import android.os.Bundle;
import android.os.IBinder;
import android.os.Message;
import android.os.Messenger;
import android.text.format.Time;
import android.widget.Toast;

import java.util.logging.Handler;

/**
 * Created by NRV on 9/3/2014.
 */
public class MyService extends Service {
int val=1;
@Override
public IBinder onBind(Intent intent) {
    return msgnr.getBinder();
}



@Override
public boolean onUnbind(Intent intent) {
    stopSelf();
    return super.onUnbind(intent);
}

class MessageHandler extends android.os.Handler{

    public  void handleMessage(Message msg){
        if (msg.what==val){
            Toast.makeText(getBaseContext(),"I am toast in service",Toast.LENGTH_SHORT).show();
            Bundle bundle=msg.getData();
            String msg_snt=bundle.getString("my_string");
            Toast.makeText(getApplicationContext(),"I recv : "+msg_snt,Toast.LENGTH_SHORT).show();
        }
        else{
            super.handleMessage(msg);
        }

    }
}

Messenger msgnr=new Messenger(new MessageHandler());


}

      

        
        
        
      

    

activity_my.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context=".MyActivity">

<TextView
    android:text="@string/hello_world"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/textView"
   />

<Button
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Start"
    android:id="@+id/button"
    android:layout_below="@+id/textView"
    android:layout_marginTop="93dp"
    android:layout_toLeftOf="@+id/button2"
    android:onClick="startMethod"/>

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Stop"
    android:id="@+id/button2"
    android:layout_below="@+id/button"
    android:layout_alignParentRight="true"
    android:layout_marginRight="106dp"
    android:onClick="stoptMethod"/>

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Run"
    android:id="@+id/button3"
    android:layout_below="@+id/button2"
    android:layout_alignParentLeft="true"
    android:onClick="runMethod"/>

</RelativeLayout>