simply Store checkbox state to sqlite database in android

I'm simply trying to store the state of checkbox in database but my application crashes when i click on submit button.I am trying to do this with a sqliteOpenHelper. After storing the state I also want to display it but first I'm not able to store it. Please guide me as I'm new to android. Here's my code..

    //MainActivity.java
    CheckBox ch1;
    Button btnSubmit;
    int checked=0;
    DatabaseHelper dbhelper;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    ch1=(CheckBox)findViewById(R.id.checkBox);
    btnSubmit=(Button)findViewById(R.id.button);

    AddData();
    }

    public void AddData() {
    btnSubmit.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            ch1.setOnCheckedChangeListener(new 
      CompoundButton.OnCheckedChangeListener() {
                @Override
                public void onCheckedChanged(CompoundButton buttonView, 
         boolean isChecked) {
                    if(isChecked){
                        checked = 1;
                    }else{
                        checked = 0;
                    }
                }
            });


            boolean insertData = dbhelper.addData(checked);

            if (insertData == true) {
                Toast.makeText(MainActivity.this, "Order Placed!", 
       Toast.LENGTH_LONG).show();
            } else {
                Toast.makeText(MainActivity.this, "Something went wrong : 
      (.", Toast.LENGTH_LONG).show();
            }
        }
    });
    }

    //databasehelper.java
    public class DatabaseHelper extends SQLiteOpenHelper {

     public static final String DATABASE_NAME = "check.db";
      public static final String TABLE_NAME = "entry";
      public static final String COL1 = "SIZE";

     public DatabaseHelper(Context context) {
    super(context, DATABASE_NAME, null, 1);
     }

    @Override
    public void onCreate(SQLiteDatabase db) {
    String createTable = "CREATE TABLE " + TABLE_NAME + "(SIZE INTEGER)";
    db.execSQL(createTable);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) 
   {
    db.execSQL("DROP IF TABLE EXISTS " + TABLE_NAME);
    onCreate(db);
   }

   public boolean addData(int s1){
    SQLiteDatabase db = this.getWritableDatabase();

    ContentValues contentValues = new ContentValues();
    contentValues.put(COL1, s1);

    long result  = db.insert(TABLE_NAME, null, contentValues);

    if(result == -1){
        return false;
    }else{
        return true;
    }
      }
    }