Android：为什么碎片吐司不会在fragmentdialog被解散时触发？

Question

我的Activity中有代码在片段中启动DatePicker。 DatePickerDialog允许用户选择日期。然后，我希望DatePickerDialog关闭（onDismiss）并显示祝酒词。什么都没发生。我在这里缺少什么？

片段文件：

public class SaveDatePickerFrag extends DialogFragment implements DatePickerDialog.OnDateSetListener {

Calendar c;
int year = 0, month = 0, day = 0;

public SaveDatePickerFrag() {
}

@Override
public Dialog onCreateDialog(@NonNull Bundle savedInstanceState) {
    super.onCreateDialog(savedInstanceState);

    c = Calendar.getInstance();
        year = c.get(Calendar.YEAR);
        month = c.get(Calendar.MONTH);
        day = c.get(Calendar.DAY_OF_MONTH);

    DatePickerDialog picker = new DatePickerDialog(getActivity(),
            this, year, month, day);
    return picker;
 }

public void onDateSet(DatePicker view, int year, int month, int day) {
     Calendar calendar = Calendar.getInstance();
     calendar.set(Calendar.YEAR,year);
     calendar.set(Calendar.MONTH,month);
     calendar.set(Calendar.DAY_OF_MONTH,day);
     txtDate = (EditText) getActivity().getWindow().getDecorView().getRootView().findViewById(R.id.EditText);
     SimpleDateFormat sdf = new SimpleDateFormat(myFormat, Locale.US);
 }

  public void onDismiss(final DialogInterface dialog) {
    super.onDismiss(dialog);
    if (getActivity() !=null) {
        // The below Toast reminds the user to click Save to proceed.
        Toast toast = Toast.makeText(getActivity(), "If done, click the Save button", Toast.LENGTH_LONG);
        toast.setGravity(Gravity.CENTER_VERTICAL, 0, 0);
        toast.show();
    }
}