GWT功能在DatePicker能够返回所选日期之前完成，如何延迟直到返回日期？

Question

The code below runs without waiting for popUpPanel (Date picker) to return a selected date by the user. I know there is a timer method for gwt but I was wondering if there is another delay method that I could use that could wait for it to return a selected date then execute the rest of the code.

 public static dateCalc(){
    Date selection = new Date();
    Date start = new Date();
    Date end = new Date();

    PopupCalendar popupCalendar = new PopupCalendar();
    popupCalendar.displayPopupCalendar();
    popupCalendar.setDate();

    while(popupCalendar.calendarVisible()){

    selection = popupCalendar.getDate();
    return date;
}

public class PopupCalendar {
    public String dateString;
    public Date date;
    public DatePicker datePicker = new DatePicker();
    final PopupPanel calendarPanel = new PopupPanel(true);

    public void displayPopupCalendar() {

        calendarPanel.setWidget(datePicker);
        calendarPanel.setGlassEnabled(true);
        calendarPanel.center();

        calendarPanel.show();


        datePicker.addValueChangeHandler(new ValueChangeHandler<Date>() {
            @Override
            public void onValueChange(ValueChangeEvent<Date> dateValueChangeEvent) {
                date = dateValueChangeEvent.getValue();
                setDate(date);
                dateString = DateTimeFormat.getMediumDateFormat().format(date);
                //System.out.println("User selected the date: " + dateString);
                calendarPanel.hide();
            }
        });


        return date;


    }

Answer 1

You have to do everything in GWT/JavaScript (in the client) asynchronously. So I'm afraid you can't block with the "while" loop.

In most cases, I think, it is best to avoid timers/delays.

It looks like you are almost there with ValueChangeHandler. Make the next thing happen when that fires?