Insert in database error in android

i have created simple app which add the 3 field's from user side when i click on add button the app is Forcefully closed there is no error syntex error in my code here is my code please someone help me and suggest me what can i do for make app like this here i put the screen shot of my app

Here is code mainActivity.java

import android.app.Activity;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends Activity {
    SQLiteDatabase db;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        OpenHelper oh = new OpenHelper(getApplicationContext()) ;
        oh.getWritableDatabase();
        final EditText e1 = (EditText) findViewById(R.id.editText1);
        final EditText e2 = (EditText) findViewById(R.id.editText2);
        final EditText e3 = (EditText) findViewById(R.id.editText3);
        final Button b1 = (Button) findViewById(R.id.button1);
        final Button b2 = (Button) findViewById(R.id.button2);
        b1.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                db.execSQL("insert into student values("+e1.getText().toString()+",'"+e2.getText().toString()+"','"+e3.getText().toString()+"');");
            }
        });

    }


    @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;
    }

The second file for database handler this is here OpenHelper.java

package com.VAP.sqlitedemo;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

public class OpenHelper extends SQLiteOpenHelper {

    public OpenHelper(Context context) {
        super(context,"MyDatabase",null,1);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub
        db.execSQL("create table student(id integer,name text,department text);");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub

    }

}