This might be a general mvp places and activities question, but the show case I'm trying to understand here is this gwtphonegap-showcase-gwt example.
How do I pass a parameter to a view from another one?
For example, let's say I want that when a user clicks on any cell on the OverviewActivity, it will take them to the same place everytime (AboutPlace), but the text should be different (let's say it contains the cell number).
I added a setText(String text) to the AboutDisplay interface with the corresponding label and setText() in the AboutDisplayGwtImpl, but I have no idea where to call it. I tried calling it in AboutActivity start() method and ClientFactoryGwtImpl getAboutDisplay() method, but they seem to be called only once when the app first loads, so I end up with the same text each time.
you should not use a view directly for that.
You can add a field on a place and set your value there and access the same value in the next activity.
Related
I want to create a rectangle button field (using list).
The "cells" in this field are basically buttons, the only thing I need to change is the OnClick event handler (I want it to check some button properties and take some action according to them).
I did something like this before in MSVS 2013, using C++/CLR, I just wrote the method I wanted to work as an event handler, added event handler variable to the "cell" constructor, and assigned it as a new event handler while "filling" the list.
It looked something like this:
.h
cell(<...>, System::EventHandler^ eh) : {
<...>;
Click += eh;
}
.cpp
List^ list = gcnew List(<...>, gcnew System::EventHandler(^Form1, &Form1::cell_Click));
Mr. Google told me that in C++ Builder inheritance of managed objects is not just writing a colon after the class declaration, it's a process called "Creating component".
Since I don't need to re-use this little piece of code, I don't want to create any packages or use existing. So I create a unit.
The questions are:
Where to write event handler declaration in header?
Where to write event handler implementation in .cpp file?
How do I actually use the written unit in the project I added it to? I mean, can I just declare a variable of the custom inherited type in the project files?
C++Builder uses C++ as its language, not "Managed C++". there is no ^ pointer types and no gcnew, or "managed objects".
To make an event handler easily, select the control in the form editor and press F11. That will bring up the Object Inspector. Select the "Events" tab and then double-click the handler you want to create. This will create the code you need, you just have to fill in the function body.
If you double-click on the control, it's a shortcut to create the most common event handler for that object (which is actually OnClick for a button, so you could just double-click your button).
(In older versions of C++Builder, if you saved your project before typing anything in the function body, it would very kindly delete the handler, which was pretty annoying -- XE5 no longer does that).
I don't quite understand what you are talking about in some of your post - why do you want to inherit from the button? I figured from your opening paragraph that you just want to create a bunch of buttons at runtime, and implement the OnClick handler.
If you mean that you just want to create a lot of buttons at runtime, then you can do it like this:
TButton *b = new TButton(this); // 'this' will be responsible for deleting the button
b->Parent = this; // `this` will be responsible for displaying the button
b->Caption = "hello";
b->OnClick = Button1->OnClick;
// set other properties
AFAIK there is no easy way to clone a button. You have to make a new button like this, and then copy the values you want from another button. Properties you don't set will have their default values.
If you use this method (i.e. make Button1 in the form editor and then copy its OnClick to your other buttons) it is nice and easy. You could actually delete your Button1 after you have used it to auto-generate the OnClick handler and give you the right function signature.
You could also store the pointers to each button in a list , e.g. std::list<TButton *>. Be mindful of button lifetimes when doing this: the fact that the button's Owner is the form means that the form will delete them during the form destruction. You should not try to delete these pointers yourself, and you should not use them during or after the form destruction.
Inside the OnClick handler, you can get a pointer to its Button by doing:
TButton *b = dynamic_cast<TButton *>(Sender);
Then you can use b->Tag or some other property of the button to identify which button was clicked.
What is the best practise to update Activity state on Place change? Imagine you have an activity with view that displays list of categories and list of items in the category. If different category is selected then app goes to new place with category ID. I want then to only refresh items and not to create new activity that also re-reads category list.
My current approach is like this:
public class AppActivityMapper implements ActivityMapper {
private ItemListActivity itemListActivity;
...
public Activity getActivity(final Place place) {
final Activity activity;
if (place instanceof ItemListPlace) {
if (itemListActivity == null) {
itemListActivity = new ItemListActivity((ItemListPlace) place, clientFactory);
} else {
itemListActivity.refresh((ItemListPlace) place);
}
activity = itemListActivity;
} else {
itemListActivity = null;
}
...
return activity;
}
...
Alternatives are:
listen to PlaceChangeEvents from within the activity (you can then use a FilteredActivityMapper and CachingActivityMapper for the caching of the activity in your ActivityMapper, so that it's reduced to only create a new activity when asked). †
have some component listen to PlaceChangeEvents and translate them to business-oriented events, the activity then listens to those events rather than PlaceChangeEvents, otherwise the same as above.
decouple the activity from the "screen", make the "screen" a singleton with a reset() method and call that method from the activity's start (possibly passing the category ID as an argument in this case). The "screen" being a singleton could then make sure to load the categories list only once.
in your case, you could also simply put the categories list in a shared cache, so that you don't have to reuse your activity by can create a new one, the categories list will be retrieved once and put in the cache, subsequent activity instances will just use what's in the cache. This is similar to the above, but simpler, and the cache could be used by other parts of the application.
I'd personally rather go with your approach though (with a small exception, see below), as it's the simplest/easiest. Decoupling the activity from the "screen" is also an option; the GWT Team started exploring this approach in the Expenses sample (decoupling the activity responsibility from the presenter responsibility with using MVP) without ever finishing it unfortunately.
Other than that, I don't think any best practice has really emerged for now.
†. I don't like coupling my activities with the places they're used with (I don't quite like the coupling for the goTo calls either, but haven't yet found a clean and simple alternative), so I'd rather not go with this option; and similarly, I'd not pass the place to the activity constructor and refresh method like you did, but rather extract the information out of the place and pass it to the activity (e.g. in your case, only give the category ID to the activity, not the ItemListPlace instance; I would then simply call setCategory in all cases, and not even pass the category ID to the constructor).
In my opinion,
The role of the ActivityMapper is to give you back an Activity from a Place.
The role of the ActivityManager is to start the Activity given back from the ActivityMapper and to stop the current one if different. In your case you would like to "update/refresh" the current Activity.
So I would modify the ActivityMapper so as it will allways give me back the same instance of Activity for a given type of Place. A good way to do so could be to use GIN and use the singleton scope ...in(Singleton.class) to inject your Activity.
If you do that, when changing the url, if the place stays the same (meaning your url has the same word after # and before :) so that the Type of your place stays the same, the ActivityMapper will give you back the same instance of Activity so the ActivityManager will do nothing on the Activity. Check l.126 of ActivityManager
if (currentActivity.equals(nextActivity)) {
return;
}
For me you have 2 options there. The first one, as Thomas said , is to listen to PlaceChangeEvent in your Activity. The new Place you will receive can have new parameters inside based on the new url given and you can "update/refresh" your Activity.
The second one, that I find more in line with the Activity/Place pattern is to modify the ActivityManager so that it calls an update(Place) method on the Activity when the Activity given back by the ActivityMapper is the same that the current Activity.
I haven't tried any of these solutions yet but I will soon ... I might be able to update that post at that time.
You can find more information in this article I wrote on my blog on that topic
Here is a little schema I made to help me understand the pattern, hope it will help :
I would not do any logic in my ActiviyMapper except returning an activity, by creating a new one or giving a previous one (or null). According to me, the mapper doesn't have to know about refresh() or what activities do.
If that, then the logic of 'refresh()' would be given to the activy through the place which holds a token. That token should be holding the information about either what is the state of the request (a new page, reload, an id, etc).
In the activity, first, it asks for the View, the one related to this activity (tip : a singleton given by a 'ClientFactory' is good practice), then it creates a presenter for that view, and bind them together.
Lastly, the activity will use the token from the place to provide any information about state to the presenter. And then, it adds the view in the page.
It's good to know by default, with places and activies, going to the same place doesn't do anything (no reload). But you can take care of it with token and activity-mapper easily.
Hope you'll find an adapted solution for you case. Goodluck.
Is there any idea wich allows me using layouts declared in MyApplication.java from other classes and functions.
I tried put them in parameters it works but it becomes very complicated
For example xhen callin a function named Y in function X I have to pass all layouts on parameters like this:
X(layout1,layout2,layout3,layout4)
{
Y(a,b,c,layout1,layout2,layout3,layout4)
}
I tried to use a class named uiHelper but it didn't works
You can take a look at Blackboard addon for vaadin.
https://vaadin.com/addon/blackboard
From that page:
Sometimes, having a deep component hierarchy poses a problem, when you need to inform a component high up in the tree that something happened deep down below. You normally have one of two choices - either pass the listener all the way down the hierarchy, leading to more coupled code, or let each component in between be a listener/notifier, passing the event all the way back up. With the Blackboard, you can register any listener to listen for any event, and when that event is fired, all the listeners for that event are triggered. This keeps your components clean and rid of unnecessary boilerplate code.
For your example, you can create a LayoutChangeListener and LayoutChangeEvent.
MyApplication can then implements LayoutChangeListener and when a LayoutChangeEvent is fired, you can change your layout without passing it around.
i learned how to implement my own SuggestionOracle("AuSuggestOracle") and own
Suggestions("AuMultiWordSuggestion"). In my case the suggestion object
is constructed with a DTO. On a selection event i need this dto (or
some fields of it) to react appropriate.
I implemented a widget containing 3 suggest boxes with this special
oracle and some logic between them. Now i want to apply MVP pattern -
split this widget in presenter and view.
At the moment the presenters display interface look like that:
public interface Display {
HasSelectionHandlers<Suggestion> getFedLand();
HasSelectionHandlers<Suggestion> getCounty();
HasSelectionHandlers<Suggestion> getCommunity();
AuSuggestOracle getFedLandOracle();
AuSuggestOracle getCountyOracle();
AuSuggestOracle getCommunityOracle();
void clearCounty();
void clearCommunity();
void activateForm();
Widget asWidget();
}
the problem is the implicit knowledge about my model in methods
returning "AuSuggestOracle". so my question is how to get the view/
interface "humble". in my case the displayed suggestion-strings are
ambiguous and i need at least the "id" of a selected item to know what
DTObject is selected.
The way I got around this is by leaving out the getters for the Oracle since once my presenter sets it my view doesn't need any information about it. So, my interface looked like this:
public interface Display {
...
void setSuggestionOracle(SuggestOracle oracle);
HasSelectionHandlers<SuggestOracle.Suggestion> getSelectionListener();
}
The problem I encountered was being able to add the suggestion to the SuggestBox after it was instantiated. To get around this, I initialized with a blank SuggestBox and then removed it from the view, updated in, and inserted it back into position.
After that, you can write your handler (in the presenter) to check if the suggestion is an instance of your custom suggestion and your presenter can handle the selection and push the relevant information back down to your view.
By doing this, all your view knows is that it will be taking generic suggestions for something, and that at some later time it will be updating with information (which will be as a result of the suggestion, but the view is to 'humble' to know that).
I am trying to figure out the best way to design something. I am writing an iPhone App and for the most part I am using async calls to a web service. This means that I cam setting up a URLConnection, calling start and letting it call me back when the data is available or an exception occurs. This works well and I think is the correct way to handle things.
For example:
I request a list of people from a web service. The resulting list is Xml Person elements which will be translated into an objective-c "Person" object by my XmlDelegate.
When I call the function to get the person, I pass in a "PersonResultDelegate", which is a protocol with a single function called "PersonReceived:(Person *)p". So, each time I get a complete Person object, I call that method and all is well. So, my detail view (or search result view) just receives the elements as they are available.
The problem comes when I need to obtain more then one specific object. In my specific case, I need to get the first and last appointment for a person. So, I need to make two API calls to obtain these two single Appointment objects. Each Appointment object will result in a call to the registered AppointmentResultDelegate, but how will I know which is the first and which is the last? I also need to somehow handle the case when there is no "first" or "last" Appointments and the Delegate will never get called.
What would be the correct way design wise to handle this? Should I add some additional context information to the initial request which is passed back to the handle in the delegate? An opaque piece of data which only makes sense to the person who made the initial call? What are my other options?
Solution
What I actually ended up doing is just passing an opaque piece of data along with the Appointment to the delegate. So, when I request an appointment object I have a method like:
getNextAppointment withDelegate:self withContext:#"next"
getPrevAppointment withDelegate:self withContext:#"prev"
This way when the delegate gets called I know what appointment is being delivered.
"Each Appointment object will result in a call to the registered AppointmentResultDelegate, but how will I know which is the first and which is the last?"
By looking at the order in which you receive these callbacks. Or by looking at some value in that xml data. Like a sequence or data. I don't know your data of course.