问在安卓系统中使用DatePicker时遇到麻烦

EN

static final int DATE_PICKER_FROM = 0;
DatePickerDialog.OnDateSetListener from_dateListener;
private EditText editDateStart;
...
private void addListenersToButtons(){
    editDateStart = (EditText)findViewById(R.id.editDateStart);

    editDateStart.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            showDialog(DATE_PICKER_FROM);
        }
    });
}

@Override
protected Dialog onCreateDialog(int id) {
    // TODO Auto-generated method stub
    switch (id) {
    case DATE_PICKER_FROM:
        return new DatePickerDialog(this, from_dateListener,2,10,2013);
    }
    return null;
}

 from_dateListener = new DatePickerDialog.OnDateSetListener() {

            // when dialog box is closed, below method will be called.
            public void onDateSet(DatePicker view, int selectedYear,
                    int selectedMonth, int selectedDay) {
                    int year = selectedYear;
                    int month = selectedMonth;
                    int day = selectedDay;

            editDateStart.setText(
                    new StringBuilder()
                        .append(pad(day)).append("/")
                        .append(pad(month + 1)).append("/")
                        .append(year).append(" "));
            }
        };

DatePickerDialog(this, from_dateListener,2,10,2013);