android - 有工作时间的时间选择器

Question

我对时间选择器有疑问：我想创建一个自动计算工作时间的应用程序（如果我从早上 8 点开始并在 11:30 结束，结果我必须有 3:30）。

    @Override
protected Dialog onCreateDialog(int id) {
    switch (id) {
    case TIME_DIALOG_ID:
        return new TimePickerDialog(this, timePickerListener, hour, minute,false);

    case TIME_DIALOG_ID2:
    return new TimePickerDialog(this, timePickerListener2, hour1, minute1,false);

    case TIME_DIALOG_ID3:
        return new TimePickerDialog(this, timePickerListener3, hour, minute,false);

    case TIME_DIALOG_ID4:
        return new TimePickerDialog(this, timePickerListener4, hour, minute,false);         

}


    return null;
}

private TimePickerDialog.OnTimeSetListener timePickerListener =  new TimePickerDialog.OnTimeSetListener() {
    public void onTimeSet(TimePicker view, int selectedHour, int selectedMinute) {
        hour = selectedHour;
        minute = selectedMinute;
        txtTime1.setText(new StringBuilder().append(padding_str(hour)).append(":").append(padding_str(minute)));
    }
};


private TimePickerDialog.OnTimeSetListener timePickerListener4 =  new TimePickerDialog.OnTimeSetListener() {
public void onTimeSet(TimePicker view, int selectedHour, int selectedMinute) {
    hour4 = selectedHour;
    minute4 = selectedMinute;
    txtTime4.setText(new StringBuilder().append(padding_str(hour4)).append(":").append(padding_str(minute4)));
    if (txtTime4 == null) {
        hour4 = 0; hour3=0; minute4=0; minute3=0;
    }

    txtTimeresult1.setText(new StringBuilder().append(padding_str((hour1-hour)+(hour4-hour3))).append(":").append(padding_str((minute1-minute)+(minute4-minute3))));

}};