the application has stopped, when i tried to clear all data

i tried to clear all data from the table inside my database, it was successfull, but the only problems is, everytime i pressed the clear button, it does clear all data but after that the application shows it has stopped

which part did i go wrong? below is my coding from my database:

public boolean deleteRow(long id) {

        SQLiteDatabase db = helper.getWritableDatabase();
        String where = data.UID + "=" + id;
        return db.delete(data.TABLE_NAME, where, null) != 0;
    }

    public void DeleteAll(){

        Cursor c = readEntry();
        long id = c.getColumnIndexOrThrow(data.UID);
        if (c.moveToFirst()) {
            do {
                deleteRow(c.getLong((int) id));
            } while (c.moveToNext());
        }
        c.close();
        return;
    }

and code from the other java:

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.showbmi);
        initializeApp();
    }
    private void initializeApp(){

        weightinputid = (EditText) findViewById(R.id.weightid);
        heightinputid = (EditText) findViewById(R.id.heightid);
        buttonBMI = (Button) findViewById(R.id.buttonBMI);
        BMIfinal= (TextView) findViewById(R.id.BMIfinal);
        BMIStatus = (TextView) findViewById(R.id.BMIstatus);
        save = (Button) findViewById(R.id.button);
        detail = (Button)findViewById(R.id.button1);
        bb = (Button)findViewById(R.id.bb);
        table_layout = (TableLayout) findViewById(R.id.tableLayout1);

        data  = new fitnessdatabase(this);
        BuildTable();
        bb.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                data.DeleteAll();
                new MyAsync().execute();
            }
        });



private class MyAsync extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {

            super.onPreExecute();

            table_layout.removeAllViews();

            PD = new ProgressDialog(Showbmi.this);
            PD.setTitle("Please Wait..");
            PD.setMessage("Loading...");
            PD.setCancelable(false);
            PD.show();
        }

        @Override
        protected Void doInBackground(Void... params) {

            String weight = weightinputid.getText().toString();
            String bmi = BMIfinal.getText().toString();
            String status = BMIStatus.getText().toString();
            String date1 = mDateText.getText().toString();

            // inserting data
            data.open();
        //    sqlcon.insertData(firstname, lastname);
            long id = data.insertData(weight, bmi, status, date1);
            BuildTable();
            return null;
        }

        }