I'm having an issue handling the forward button.
Basically, when a user is on a page and has made changes without saving then presses the backwards or forwards button they are presented with a prompt and two options: Leave or Stay.
I have implemented the backwards button fine, and choosing to stay on the page works well using History.newItem(currentToken) - the back button is still clickable.
However with the forwards button, if I use History.newItem(currentToken), it brings this to the front of the history stack and the forward button can no longer be clicked.
History.replaceItem(currentToken) causes the same issue.
How do I handle the cancelling of a forwards action so that I stay on my current page, but the forwards button is still enabled?
#Override
public void onValueChange(ValueChangeEvent<String> event) {
logger.info("back button pressed: " + event.getValue());
String evenVal = event.getValue();
String token = History.getToken();
AbstractPresenter presenter = sessionKiosk.getCurrentlyShowingPresenter();
if (presenter instanceof NSRCommonWorksheetPresenter && sessionKiosk.isDirty()) {
((NSRCommonWorksheetPresenter)presenter).setHistoryToken(event.getValue());
((NSRCommonWorksheetPresenter)presenter).showUnsavedChangesLeavingPageDialog();
}
else {
handleHistoryEvent(event.getValue());
}
}
The dialog is shown and when I click on stay on page the following is called.
public void stayOnCurrentPage() {
if (eventMap.get(prevPage) != null) {
History.newItem(prevPage, false);
}
}
Update: Basically history.newItem(value) removes the use of the forward button. Is there another way to cancel the event? If I just do nothing, th page stays where i want but the url still updates
None of the 3 options in the else statement seem to work.
Thanks.
You can simply cancel the event without touching History or tokens.
UPDATE:
It appears from your code that you are not intercepting the event (back/forward button), but let it go through, get the new token, and then force a return to the previous state under certain circumstances.
I suggest using Activities and Places pattern where every "place" within your app has a corresponding "activity". Each activity in your app will implement GWT Activity interface which includes mayStop() method. This method is called before a user navigates away from a specific place in your app, giving you an opportunity to warn a user and cancel the navigation if necessary.
In general, this pattern offers a very robust support for the History mechanism, covering many use cases.
If you want to support History mechanism yourself, take a look at PlaceChangeRequestEvent - it allows you to warn a user who tries to navigate away from a place in your app.
Related
First off, before the flames start, I do know that trying to hinder the back button in the browser is a dumb idea. I would not try to do this, but my business partners are very insistent on it. We are porting an existing .exe to the web and their definition of this is 'run it in a browser' and not "make it a web site". So, fact that it's a bad idea (I agree), here's the question:
Is there a way to ignore or trick the GWT PlaceController / History manager mechanisms so that when the back button is pressed, it just stays on the same page?
I have used Window.addWindowClosingHandler to add a handler which will prompt the user if they want to leave the page and overriden the newItem() method of the defaultHistorian so that no history is tracked at all, but this isn't quite what the business people want.
What they'd like is to just ignore the back button so that nothing happens when it is clicked.
If anyone knows how to do this with GWT, I'd be very grateful.
And I"ve done a lot of google searching and haven't found anything exactly like this question. At least, not close enough to help.
I was able to get GWT to not accumulate any history so that when the user presses the BACK button, they cause an onWindowClosing event to happen and the Browser will prompt them if they want to stay or leave. This will accomplish the goal of not allowing the BACK button to take them back, but it's a bit Draconian. This code does that:
class TvHistorian extends PlaceHistoryHandler.DefaultHistorian
{
#Override
public void newItem(String token, boolean issueEvent) {
// don't do anything - this will prevent history from accumulating
}
}
final PlaceHistoryHandler historyHandler = new PlaceHistoryHandler(historyMapper, new TvHistorian());
I've tried a bunch of stuff including extending the PlaceController.goTo() to save the "lastNormalFlowPlace". Then, I tried to override the History.onValueChange to use this saved Place if it was different than what the event specified. But I think I missed some subtlety because that didn't work as expected.
With the above exception, my code looks almost exactly like what is documented here: http://www.gwtproject.org/doc/latest/DevGuideMvpActivitiesAndPlaces.html#Putting_it_all_together
I have already posted an answer in the same context.
Please have a look at below links:
promt user on backspace and browser backbutton in gwt
how can i get a prompt on url change
Disable back button in GWT
Try with any option:
History.addValueChangeHandler
WindowClosingHandler
Event.addNativePreviewHandler
$wnd.onbeforeunload
--EDIT--
Sample code: (It's working perfectly fine in Firefox, Chrome as well as IE9)
Note: add below code in the beginning of the onModuleLoad() method.
final String initToken = "Place";
History.addValueChangeHandler(new ValueChangeHandler<String>() {
#Override
public void onValueChange(ValueChangeEvent<String> event) {
String token = event.getValue();
if (!initToken.equalsIgnoreCase(token)) {
History.newItem(initToken);
}
}
});
// fire the initial history state.
History.fireCurrentHistoryState();
Note: add checks for other allowed history tokens.
Ok, let see how traditional non-Ajax page work. Suppose you have a page like the below link
abc.com#!search;item=car
In the traditional non-Ajax website, when first time you call "abc.com#!search;item=car", it will go to server and get data. After that you go to other page like "abc.com#!customer;name=tom" and then you hit back button it will go back to "abc.com#!search;item=car". However, this time it won't call to the server again cos it remembered it did before.
Now Here is the GWTP problem. Suppose the above abc.com was built in GWTP technology.
At the first time wen user enters the "abc.com#!search;item=car", the GWTP app will initialize the page "search" via onBind, then the prepareFromRequest will be called & it will go to server to get data.
That is Good, no problem. However, if we open a new page (like customer page) by using revealPlace, then we hit the back button it will go back to "search" page & it will call prepareFromRequest again. The prepareFromRequest will then make the exactly same call to server again. That is not good cos it wastes resource.
So I want the "prepareFromRequest" to be called ONLY at the time we initialise the page (run after onBind) & block the "prepareFromRequest" in all other page request (ex like user press the back button).
It mean "prepareFromRequest" should work just like traditional non-Ajax page mentioned above.
Can we do that? or
Do you have a better solution?
Why don't you just check in your prepareFromRequest method if you have already a search result for that specific searchterm and only issue a call to the backend if it has changed?
Something like this:
public Presenter extends .... {
String searchItem = null;
List<DTO> searchResult = null;
#Override
public void prepareFromRequest(PlaceRequest placeRequest) {
super.prepareFromRequest(placeRequest);
String item = placeRequest.getParameter("item",null));
if (searchItem == null || !searchItem.equals(item)) {
searchItem = item;
// MAKE A CALL TO THE BACKEND AND STORE THE DATA IN A FIELD.
searchResult = GET_FROM_SERVER(searchItem);
}
}
}
I have a hook on the beforeUnload event. If i try to click on a link, reload or close the tab or the navigator, the app ask for confirmation before leaving. That's the desired behavior.
But if click on the back button or the backspace outside an input, no confirmation.
At the beginning of the html :
window.onbeforeunload = function() {
if (confirmEnabled)
return "";
}
And i use the Gwt PlaceHistoryMapper.
What did i miss ? Where did i forgot to look ?
Thanks !
As long as you stay within your app, because it's a single-page app, it doesn't by definition unload, so there's no beforeunload event.
When using Places, the equivalent is the PlaceChangeRequestEvent dispatched by the PlaceController on the EventBus. This event is also dispatched in beforeunload BTW, and is the basis for the mayStop() handling in Activities.
Outside GWT, in the JS world, an equivalent would be hashchange and/or popstate, depending on your PlaceHistoryHandler.Historian implementation (the default one uses History.newItem(), so that would be hashchange).
I am using GWTs Activities and Places pretty much as described on http://code.google.com/webtoolkit/doc/latest/DevGuideMvpActivitiesAndPlaces.html and it is all working fine.
What I would like to do is from a particular page navigate to the previous page without using History.back() as I don't want to lose the history state. (I have a page where the user performs an action, on success I want to return to the previous page and keep the history state, on the other hand if they cancel I do want to use History.back() as I do want to lose the state).
The only way I can think of to do this is to create my own Place/History tracking code that listens to Place/History change events and makes the previous Place available to me so that I can call placeController.goto(...)
Is there an easier way of doing this? Am I missing something?
The approach I took was to store the history token in code (as suggested). I extended PlaceController and used it to track Place changes on the EventBus. Now everywhere I was using PlaceController I instead use PlaceControllerExt which has a nice previous() method that takes me back to where I came from - but navigates forward and never leaves the application.
public class PlaceControllerExt extends PlaceController {
private final Place defaultPlace;
private Place previousPlace;
private Place currentPlace;
public PlaceControllerExt(EventBus eventBus, Place defaultPlace) {
super(eventBus);
this.defaultPlace = defaultPlace;
eventBus.addHandler(PlaceChangeEvent.TYPE, new PlaceChangeEvent.Handler() {
public void onPlaceChange(PlaceChangeEvent event) {
previousPlace = currentPlace;
currentPlace = event.getNewPlace();
}
});
}
/**
* Navigate back to the previous Place. If there is no previous place then
* goto to default place. If there isn't one of these then it'll go back to
* the default place as configured when the PlaceHistoryHandler was
* registered. This is better than using History#back() as that can have the
* undesired effect of leaving the web app.
*/
public void previous() {
if (previousPlace != null) {
goTo(previousPlace);
} else {
goTo(defaultPlace);
}
}
}
You have to somehow keep track of were to return, because instead of cancel the user can hit the back button, which would be the same as clicking cancel, except there is no code in your application executed, so you have no control.
Secondly if you have the history in the url, the user could navigate directly to that page and then you should know where to go to when the user click ok. Or if the user goes directly to the page, redirect the user to another page.
One approach is to store the return history token in the history token of the page you go to. When the page is finished it can go back(or technically it would be 'go forward') to that page based on the passed return token. (Although with GWT you could easily store the history token in code).
I have a web app that uses GXT (version 1.2.2) grids extensively. I'd like to warn the user if they make changes but don't save.
When I use the grid in a popup dialog, the only way for the user to leave is via a button (either Close or OK). If I add a SelectionListener to the Close button, I can do my "isDirty()" check and warn the user.
If I am not using a dialog, the restriction for leaving the page isn't there. The user can click on a side menu, select a different tab, hit a refresh or next page button that we have on each page. I could listen for an event on everyone of those, but is there an easier way? Something like a "before unload" event that gets fired?
Window.addCloseListener
Or in GWT 1.6:
Window.addCloseHandler
You cannot prevent the window from closing, but you can prompt the user to click cancel which will leave the page open. You can also perform a last-chance save operation after the user chooses to confirm the window close, but before your page is unloaded.
Try this:
Window.addListener(Events.Close,
new Listener<ComponentEvent>() {
public void handleEvent(ComponentEvent be) {
//Do something
}
});
or
Window.addListener(Events.Detach,
new Listener<ComponentEvent>() {
public void handleEvent(ComponentEvent be) {
//Do something
}
});