Pickers

Android 提供了time picker 和 data picker可以让用户选择有效的时间和日期.
可以使用DialogFragment 来显示一个TimePickerDialog。这样的话，必须实现DialogFragment 的子类，然后在fragment的onCreateDialog()中返回TimePickerDialog。其次必须要实现TimePickerDialog.OntimeSetListner 来得到用户设定的当前时间.
下面是一个例子：
public static class TimePickerFragment extends DialogFragment
                            implements TimePickerDialog.OnTimeSetListener {


    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        // Use the current time as the default values for the picker
        final Calendar c = Calendar.getInstance();
        int hour = c.get(Calendar.HOUR_OF_DAY);
        int minute = c.get(Calendar.MINUTE);


        // Create a new instance of TimePickerDialog and return it
        return new TimePickerDialog(getActivity(), this, hour, minute,
                DateFormat.is24HourFormat(getActivity()));
    }


    public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
        // Do something with the time chosen by the user
    }
}
实现DialogFragment的子类后。就可以直接调用DialogFragment的show()方法来显示。
下面这个例子，我们定义一个button 按键，当用户点击这个按键是，我们就显示TimePicker。
<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/pick_time"
    android:onClick="showTimePickerDialog" />
button的回调函数是showTimePickerDialog
public void showTimePickerDialog(View v) {
    DialogFragment newFragment = new TimePickerFragment();
    newFragment.show(getSupportFragmentManager(), "timePicker");
}




日期picker完全类似timer picker。也是要实现DialogFragment，但是在onCreateDialog中new一个DatePickerDialog。
public static class DatePickerFragment extends DialogFragment
                            implements DatePickerDialog.OnDateSetListener {


    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        // Use the current date as the default date in the picker
        final Calendar c = Calendar.getInstance();
        int year = c.get(Calendar.YEAR);
        int month = c.get(Calendar.MONTH);
        int day = c.get(Calendar.DAY_OF_MONTH);


        // Create a new instance of DatePickerDialog and return it
        return new DatePickerDialog(getActivity(), this, year, month, day);
    }


    public void onDateSet(DatePicker view, int year, int month, int day) {
        // Do something with the date chosen by the user
    }
}
也是定义一个button来显示datepicker
<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/pick_date"
    android:onClick="showDatePickerDialog" />
button的回调函数是showDatePickerDialog
public void showDatePickerDialog(View v) {
    DialogFragment newFragment = new DatePickerFragment();
    newFragment.show(getSupportFragmentManager(), "datePicker");
}