Aw: Re: Question about new activities on place changes
In that case I do not wanna cache things on client side. The app should be smart enough that it doesn't try to reload the list each time a list item is selected. -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-web-toolkit/-/CeWbGO49r8EJ. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
Aw: Re: Question about new activities on place changes
Thanks I will try that. Haven't thought of a FilteredActivityMapper. I already tried a CachingActivityMapper on its own and because of the equality stuff it doesn't work. I have just went through some examples but the layoutmvp example posted in this group also has an activity that starts over and over again on list selections (but data is local. If it was remote, everytime a request would be done) and the Expenses sample you have mentioned just has one activity mapper that holds one instance of its list and detail activities and calls updateForPlace(...) on them. So no new, clean activities..its more a singleton approach. Also there is no FilteredActivityMapper/CachingActivityMapper that wraps the ExpensesActivityMapper. Maybe you mean a different example? In mobilewebapp its not used either. -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-web-toolkit/-/uHhM2sXfYKAJ. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
Aw: Re: Question about new activities on place changes
Its pretty easy. If you have looked at the source code of
CachingActivityMapper you see that it only calls place.equals(lastPlace) to
check if it has to return the previous activity or has to create a new one.
After construction of CachingActivityMapper both lastPlace and lastActivity
are null and thus the first place.equals(lastPlace) will always return false
and a new Activity for that requested place is created. Lets say the first
place change has been done via placeController.goTo(new EntityPlace(1)) and
now a second place change occur via placeController.goTo(new
EntityPlace(2)).
The CachingActivityMapper will not return a cached activity if you do not
have overwritten .equals() and .hashcode() in the EntityPlace class. If you
do not overwrite both methods, the ones from Object will be used and
.equals() in Object does a instance check (return this == other). But as you
create new instances of EntityPlace the equals call in CachingActivityMapper
will always be false.
So if you overwrite equals/hashcode you would normally check if the class
types are the same and if all variables (= internal state) are the same. If
both is true then both places are equal. But even with such an equals method
in EntityPalce the CachingActivityMapper still does not work because now new
EntityPlace(1).equals(new EntityPlace(2)) is still false as they do not have
the same internal state.
Thats why you use a filter. In your Place filter(Place place) method you
would do something like:
Place filter(Place place) {
if(place instanceof EntityPlace) {
return new EntityPlace(null);
}
}
So you "nullify" that state of the place and now the CachingActivityMapper
will always receive an EntityPlace without any state information and thus
equals will return true and thus the cached activity for that place type
will be reused. So thats the basic idea on how to make CachingActivityMapper
work. By the way the PlaceController will of course always have the correct
Place with the correct internal state if you call
placeController.getWhere().
In my case I've done it in a slightly other way. So I have taken my
MainActivityMapper of my application and in its getActivity method I do:
Activity getActivity(Place place) {
if(place != null && this.lastPlace != null && place.getClass() ==
this.lastPlace.getClass()) {
return this.lastActivity;
}
this.lastPlace = place;
if(place instanceof XYZPlace) {
return new XYZActivity(place);
} else if() {.} .
}
That way I will always get a cached activity if two or more places in a row
have the same type. So basically I integrated the caching into my normal
MainActivityMapper and I do not need an extra Filter and do not need GWT's
CachingActivityMapper.
As every activity is now cached it has to implement PlaceChangeEvent.Handler
to get notified on each place change. That way the activity can update its
state based on the place although the activity is cached. In the way I did
it I wouldn't need to implement .equals/hashcode in my places but I have
done it because placeController will not fire a place change event if two
places are equal (maybe you somehow accidentally called
placeController.goTo(new EntityPlace(1)) twice in a row).
But keep in mind that I do it that way because I have only one
ActivityMapper and one Activity for each Place. It was the easiest solution
for me at the time being because I migrate the app to Activities and my
activities deal with both list selection and loading of the selected object.
But maybe my example shows you that its always a bit application dependent
how to implement things. Once you got the basic idea how you can cache
activities you can make it fit into your application.
-- J.
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Re: Aw: Re: Question about new activities on place changes
It must have been in an earlier version. It's still in the bikeshed's Scaffold app (thus probably in any app generated by Spring Roo btw) -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-web-toolkit/-/XdjnX_LgshEJ. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
Re: Aw: Re: Question about new activities on place changes
thx to all 3 of you! my very little example is now working (is there a place to upload examples? it is nice to understand activities and places without MVP) "placeController.getWhere()" is the essence that made it clear for me. thats the place the comparison uses with the place given to goTo, right? But Jens how you implemented this.lastActivity in your Mapper? Probably i will change my code again. As i mentioned in some other thread, i had code looking like yours (one mapper and one main activity with control over many presenters). You stated "Ok a Custom "CachingActivityMapper" was easy to implement and works but there is still a case I am not happy with..." With that you mean your special inside-mapper-caching? Please tell how this works (probably with saving activity in some global field?) the loop way via filtered and cached mappers used for such simple use cases (just let a presenter/acivity be) still don't feels good. -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-web-toolkit/-/el11u9TBkZYJ. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
Aw: Re: Aw: Re: Question about new activities on place changes
Hm I have tried it now and at least the activity does not get restarted. But now if I bookmark my selected employee and access it later it can not be reselected because the activity filter always sets the employee id to null. The filter can not distinguish if the app is running and the user just selects/switches between employees or if the app has just been started via a bookmark and the employee id should not be nullified. So I have to make the filter a lot smarter. Just using placeController.getWhere() does not work as it already returns the new place so I can not make any decisions based on the old place. Of course I could set a flag in the place and let the activity control if the place should be filtered or not by setting the flag to true, but I think such a flag is not really an information that should go into a place as it does not really belong to the current app state. But I think its the only solution, isn't it? I am really confused why I have these "complications". Implementing places was really nice but now with "one shot activities" it somehow gets more difficult like I would expect. Currently it somehow feels easier to have singleton activities and then deal with activity updates when a new place has been set. Well but I favor a non singleton approach as I do not like to store singleton instances that I do not need. How do you handle these place changes where the place actually keeps the same but the state changes? Do you really make the filter smarter so it can decide if it should nullify states to make places comparable or do you just live with it and create new activities and reload the data (possible via a cache, something simple like a static variable in the activity) each time they start? Am I somehow in a special situation because I do not have separate xyzListPlace/xyzDetailPlace classes along with two display areas/activity mappers and xyzListActivity/xyzDetailActivity like any other example I have seen so far? On a first thought I assume it wouldn't make a difference...?! -- J. -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-web-toolkit/-/pAHIXOoO3PYJ. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
Aw: Re: Aw: Re: Question about new activities on place changes
Oh yeah small typo in my MainActivityMapper example. It has to be:
if(place instanceof XYZPlace) {
this.lastActivity = new XYZActivity(place);
return this.lastActivity;
} else if() {.} .
So its just implemented as a field that stores the activity. Nothing fancy
;-)
-- J.
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Re: Aw: Re: Aw: Re: Question about new activities on place changes
Oh, so you have a single activity handling both the "master" and "details"? In that case, then I'd probably implement the "caching" "by hand" in the ActivityMapper (or in your own "proxy" activity mapper, inspired by CachingActivityMapper but doing the comparison using a more "sofisticated" approach than with a simple .equals()). We did just that for a couple of places in our app. -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-web-toolkit/-/iN4fY_pxYB8J. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
Re: Aw: Re: Aw: Re: Question about new activities on place changes
thx that's realy nice - on first sight much better than filtering/caching/overriding equal just to get the same as before. -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-web-toolkit/-/W5UDjjJdQqgJ. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
Aw: Re: Aw: Re: Aw: Re: Question about new activities on place changes
Yeah its a migration to activities and for simplicity I have only defined a single display area. Thats somehow the "work area" of the app. The reason is that I have a custom widget (layout panel) that can do quite a lot of things. So for each place I have that custom widget that effectively wraps a list selection, toolbar and the "real" content area and that widget goes into the display area associated with my activity manager. So my Activity has to handle both: list selection and loading the selected item. I have thought about removing the list out of that widget and instead create a separate display area/activity for it.. but that would result in to much refactoring for an initial migration to activities as that custom widget is used everywhere in the app. Well and I haven't had a clue that not doing so would lead to the "problems" I now have :) If I would have two separate display areas, only the one displaying the list selection would need that place filtering/caching, right? I'll take a look at a custom CachingActivityMapper.. we'll see. --J. -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-web-toolkit/-/CZR_e8KQoxcJ. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
Aw: Re: Aw: Re: Aw: Re: Question about new activities on place changes
Ok a Custom "CachingActivityMapper" was easy to implement and works but there is still a case I am not happy with. If a user bookmarks EmployeePlace(1,123) and 123 gets deleted the activity would redirect to EmployeePlace(1, null) to keep the URL in sync (activity can not preselect the deleted item). But now the user could hit the browsers back button and is back on the URL for EmployeePlace(1,123). But as my activity now does not get notified (its cached and no start or setPlace is called) it can not redirect again to EmployeePlace(1, null). Thus nothing would be selected but the URL would imply that something should be selected. So as I can not recreate the activity (the list would reload) the only way to solve this problem would be to call setPlace on the cached activity each time the place changes and let the activity react. But this is the same thing I would do if my activities were singletons. The only difference is that now I have only one variable storing the last activity (vs. all activities being singletons which would need a bit more memory). -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-web-toolkit/-/55xlM-38tfsJ. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
Re: Aw: Re: Aw: Re: Aw: Re: Question about new activities on place changes
Because you activity lasts longer than "a place", it should listen to PlaceChangeEvent (as if it were a singleton, except that it can be garbage collected and will be recreated if you go to another activity in the mean time), or the ActivityMapper should update it with the new place. But actually, I wouldn't do a "redirect" if I were you. I'd rather either do as if there was no id in the place (despite being one in the URL) or display an error message that the request employee (or whatever) doesn't exist. -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-web-toolkit/-/Gv_o8tY1xOoJ. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
