Java 如何获取GWT中的最后一个历史标记
我想获取导航的上一个标记 例如,在本页中: 我不知何故被重定向到这个新页面: 现在,如果我想要当前令牌,我可以通过以下方式轻松获得: 字符串currentPlace=placeManager.getCurrentPlaceRequest().getNameToken()Java 如何获取GWT中的最后一个历史标记,java,gwt,token,history,Java,Gwt,Token,History,我想获取导航的上一个标记 例如,在本页中: 我不知何故被重定向到这个新页面: 现在,如果我想要当前令牌,我可以通过以下方式轻松获得: 字符串currentPlace=placeManager.getCurrentPlaceRequest().getNameToken() currentPlace将收到“page2”,但我不知道如何获取上一个令牌,即“page1”我不知道为什么您的应用程序会出现page1重定向到page2的问题,但这里是。我扩展了place控制器,以便可以执行goBackOr
currentPlace将收到“page2”,但我不知道如何获取上一个令牌,即“page1”我不知道为什么您的应用程序会出现page1重定向到page2的问题,但这里是。我扩展了place控制器,以便可以执行goBackOr(place)。这将允许您获得前一个位置。您可以调用getPreviousPlace()。当您有一个编辑活动并且希望返回到用户来自的前一个地方时,这可能是处理位置导航的有用方法。至少出于测试目的,您应该能够在不进行任何更改的情况下使用此place controller进行替换
public class PlaceController extends com.google.gwt.place.shared.PlaceController {
private static final Logger log = Logger.getLogger(PlaceController.class.getName());
private final EventBus eventBus;
private final Delegate delegate;
private Place where = Place.NOWHERE;
/**
* Previous place from history.
*/
private Place previousPlace = null;
/**
* Legacy method tied to the old location for {@link EventBus}.
*
* @deprecated use {@link #PlaceController(EventBus)}
*/
@Deprecated
public PlaceController(com.google.gwt.event.shared.EventBus eventBus) {
this((EventBus) eventBus);
}
/**
* Legacy method tied to the old location for {@link EventBus}.
*
* @deprecated use {@link #PlaceController(EventBus, Delegate)}
*/
@Deprecated
public PlaceController(com.google.gwt.event.shared.EventBus eventBus, Delegate delegate) {
this((EventBus) eventBus, delegate);
}
/**
* Create a new PlaceController with a {@link DefaultDelegate}. The
* DefaultDelegate is created via a call to GWT.create(), so an alternative
* default implementation can be provided through <replace-with> rules
* in a {@code .gwt.xml} file.
*
* @param eventBus
* the {@link EventBus}
*/
public PlaceController(EventBus eventBus) {
this(eventBus, (Delegate) GWT.create(DefaultDelegate.class));
}
/**
* Create a new PlaceController.
*
* @param eventBus
* the {@link EventBus}
* @param delegate
* the {@link Delegate} in charge of Window-related events
*/
public PlaceController(EventBus eventBus, Delegate delegate) {
super(eventBus, delegate);
this.eventBus = eventBus;
this.delegate = delegate;
delegate.addWindowClosingHandler(new ClosingHandler() {
public void onWindowClosing(ClosingEvent event) {
String warning = maybeGoTo(Place.NOWHERE);
if (warning != null) {
event.setMessage(warning);
}
}
});
}
/**
* Get the previous place, if null then this is the first place.
*
* @return a {@link Place} instance
*/
public Place getPreviousPlace() {
return previousPlace;
}
/**
* Returns the current place.
*
* @return a {@link Place} instance
*/
public Place getWhere() {
return where;
}
/**
* Request a change to a new place. It is not a given that we'll actually
* get there. First a {@link PlaceChangeRequestEvent} will be posted to the
* event bus. If any receivers post a warning message to that event, it will
* be presented to the user via {@link Delegate#confirm(String)} (which is
* typically a call to {@link Window#confirm(String)}). If she cancels, the
* current location will not change. Otherwise, the location changes and a
* {@link PlaceChangeEvent} is posted announcing the new place.
*
* @param newPlace
* a {@link Place} instance
*
*/
public void goTo(Place newPlace) {
log().fine("goTo: " + newPlace);
// if (getWhere().equals(newPlace)) {
// log().fine("Asked to return to the same place: " + newPlace);
// return;
// }
String warning = maybeGoTo(newPlace);
if (warning == null || delegate.confirm(warning)) {
previousPlace = where;
where = newPlace;
eventBus.fireEvent(new PlaceChangeEvent(newPlace));
}
}
/**
* This is useful for going back unless there is,
* not a previous place, commonly when a user refreshes
* the screen and then tries to click back.
* @param place Place to go if there is not a previous place set.
*/
public void goBackOr(Place place) {
Place previousPlace = getPreviousPlace();
if (previousPlace != null && previousPlace != Place.NOWHERE) {
goTo(previousPlace);
} else if (place != null) {
goTo(place);
} else {
throw new RuntimeException("Previous place was null and the optional place was not specified");
}
}
/**
* Visible for testing.
*/
private Logger log() {
return log;
}
private String maybeGoTo(Place newPlace) {
PlaceChangeRequestEvent willChange = new PlaceChangeRequestEvent(newPlace);
eventBus.fireEvent(willChange);
String warning = willChange.getWarning();
return warning;
}
}
例如,您可以将此代码添加到onModuleLoad()方法中,或者添加到在应用程序开始时创建的类中,当然之后不会销毁
private Place previousPlace;
private Place currentPlace;
eventBus.addHandler(PlaceChangeEvent.TYPE, new PlaceChangeEvent.Handler() {
public void onPlaceChange(PlaceChangeEvent event) {
previousPlace = currentPlace;
currentPlace = event.getNewPlace();
}
});