EditText password;
TextView tvusername;
Button signIn;
SQLiteDatabase db=null;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.log_in);
    db = openOrCreateDatabase("mydb", MODE_PRIVATE, null);

    tvusername = (TextView) findViewById(R.id.tfuser);
    password = (EditText) findViewById(R.id.etMpinnumber);
    signIn = (Button) findViewById(R.id.btnlogin);
    db.execSQL("create table if not exists login(firstname varchar, lastname varchar, email varchar, mobile varchar, dob varchar, password varchar)");

    Cursor s = db.rawQuery("select firstname +' '+lastname AS username from login", null);
    s.moveToFirst();
    if(s.getCount()>0){
    tvusername.setText(s.getString(s.getColumnIndex("username")));
    }
    else{
        Intent i=new Intent("com.tubotechno.SignUp");
        startActivity(i);
    }
}