[英]how to get the last history token in GWT
我想获取导航的上一个标记。
例如,在此页面中:
http://www.example.com/com.example.gwt.HistoryExample/HistoryExample.html#page1
我以某种方式重定向到这个新页面:
http://www.example.com/com.example.gwt.HistoryExample/HistoryExample.html#page2
现在,如果我想要当前令牌,则可以通过以下方式轻松获得它:
字符串currentPlace = placeManager.getCurrentPlaceRequest()。getNameToken();
currentPlace将收到“ page2”,但我不知道如何获取先前的令牌“ page1”
我不确定为什么将您的应用程序问题从page1重定向到page2,但是问题就在这里。 我扩展了位置控制器,以便可以执行goBackOr(Place place)。 这将使您获得以前的位置。 您可以调用getPreviousPlace()。 当您有编辑活动并且想返回用户来自的前一个位置时,这可能是处理位置导航的有用方法。 您应该能够使用该位置控制器进行替换,而无需进行至少出于测试目的的更改。
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,您可以在onModuleLoad()方法中或在应用程序开始时创建的类中添加此代码,然后当然不将其销毁。
private Place previousPlace;
private Place currentPlace;
eventBus.addHandler(PlaceChangeEvent.TYPE, new PlaceChangeEvent.Handler() {
public void onPlaceChange(PlaceChangeEvent event) {
previousPlace = currentPlace;
currentPlace = event.getNewPlace();
}
});
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