I am using my android phone with API 15 as a testing device. I try to run this application and it'stops running on my device just after it's loaded

It's fairly simple. I am trying to learn how to establish sqlite connection for an android application. I am using Android Studio to write the code. When I try to load the app on my testing device - Android Phone of API 15 - a white screen flashes and an alert box pops up saying "LearnDB has stopped working".

Please tell me where I am going wrong.

IMPORTANT NOTE- Please try to explain how a sqlite connection should be exactly established and what rules should I definitely keep in mind while doing the same. Feel free to tell me any good programming practices while working with sqlite for android.

This is my MainActivity.java file.

    package com.example.summer.learndb;

    import android.database.sqlite.SQLiteDatabase;
    import android.app.Activity;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.Button;
    import android.widget.Toast;

    public class MainActivity extends Activity {

        private SQLiteDatabase db ;
        public static final String DB_NAME = "scoreDb.db";
        public static final int DB_VERSION = 1;
        public static final String CREATE_DB_TABLE = "CREATE TABLE IF NOT         EXISTS scoreTable (score1 INTEGER, score2 INTEGER);";
        public static final String DB_TABLE = "scoreTable";
        Button b1= (Button) findViewById(R.id.button1);
        Button b2 = (Button) findViewById(R.id.button2);

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            db = openOrCreateDatabase(DB_NAME,         SQLiteDatabase.CREATE_IF_NECESSARY,null);
            db.close();
            try{
                db.execSQL(DB_TABLE);
                db.close();
                Toast.makeText(getBaseContext(),"Table created!!!",Toast.LENGTH_LONG).show();
            }
            catch(Exception e){
                Toast.makeText(getBaseContext(),"ERROR!!!!", Toast.LENGTH_LONG).show();
            }

            b1.setOnClickListener(new View.OnClickListener(){
                @Override
                public void onClick(View v){

                }
            });
            b2.setOnClickListener(new View.OnClickListener(){
                    @Override
                    public void onClick(View v){

                    }
            });
        }
    }

This is my activity_main.xml file.

    <LinearLayout xmlns:android="http://ift.tt/nIICcg"
        xmlns:tools="http://ift.tt/LrGmb4"
        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"
        android:orientation="vertical"
        tools:context=".MainActivity">

        <Button
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:text="add"
            android:id="@+id/button1" />
        <Button
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:text="show"
            android:id="@+id/button2" />

    </LinearLayout>