Im new to GWT, this should be a simple question i hope.
Imagine that i made two Uibinders Modules or two independent widgets.(this a simplify example to expose my problem)
one is a set of buttons (ButtonPanel) and the other image to been show when i press a button from the previous panel(ImagePAnel) with a label to be the title of the image.
How can i reach the wiget the imagePanel to actuate when there are a handler click from the buttons in the (ButtonPanel)
Thanks for the help.
I recommend you to use MVP Pattern for Development and add all events in the Presenter.
Or Else you can use the following technique within the UIBinder's Java File
#UiHandler(value={"openButton"})
public void onOpenButtonClick(ClickEvent clickEvent){
//ADD THE BUTTON LOGIC HERE
}
Just Create an Object of the Images & the ImagePanel to be loaded and add it on button click using this.
I can't say I understand exactly what you are trying to accomplish but in general the best way for different components in a GUI application to communicate is to use the eventbus pattern. There's one global Eventbus object in the application that lets components subscribe to a specified type of event that are fired from any place in your application. This way you avoid spaghetti code and your components are loosely coupled.
http://code.google.com/webtoolkit/articles/mvp-architecture.html#events
I typically create a third component that is the container for the Button and Image components you defined. This component sets itself as a callback for the two and contains logic to integrate the two.
Related
https://github.com/brianchance/MvvmCross-UserInteraction is a very nice plugin for showing cross platform Alerts!
But for this question, can we assume it can not use a UIAlertView (or some other top level MessageBox type call on other platforms) but needs to show a Message within a given subsection of the screen (i.e. on IPhone you would need to supply a UIView to the plugin which it will use to show the message within).
So, how would you set this up so the ViewModel knows what View to use as its display container?
As a specific example, if I wanted an Error Service, as so -
public interface IErrorPFService
{
void Show();
void Hide();
void SetErrors(List<Error> errors);
}
and I create a platform specific implementation for it.
If I inject this into my ViewModel so it can control Error Show/Hide/Set how do I tell it the UIView (or equivalent) that I want my Errors to show within?
Can I just expose the IErrorPFService field as a public property and do -
MyViewModel.ErrorPFService = new ErrorPFService(View);
in my ViewDidLoad ...
Or is this coupled incorrectly vs Mvvm Practice?
I would expect the ViewModel to subscribe itself to the ErrorService.
When receiving a message it would expose it in a collection(?) and the View would bind to that collection.
This way the View is unknown to the service and the ViewModel has the chance to influence the View contrary to your solution.
It would help if you could give an example for the scenario you are describing.
Sometimes, the way you visually want to display something might not be the best way, so if it's possible for you, you might find a different and simpler way, which spares you from having to find a solution regarding what you are describing.
Generally, I always do the best I can to avoid the idea of having to actually pass a 'view' or an abstraction of it, from the view-model to view. Also, cross-platform wise, things can work very different in terms of UI interaction. You can find yourself in a situation when things are complicated just because UI works differently than what you expected.
But let's try find another perspective:
At any given point, the view knows what data \ feature it's displaying. So when you are calling from the view-model an user interaction action (by a service, property change, event, etc) the view should 'expect' it.
For example, the platform specific user interaction implementation is able to get the currently displayed top-view and interact it in a platform specific manner or based a relationship. In your example, the message-box can be displayed in a specific sub-view of the top level view.
In advanced scenarios, I guess you could try to create a cross-platform approach for this, but you should try to put in balance all the abstraction you want to create just for that. Think about doing this as a plan ... Z. If possible. Again, giving an example might help.
We've been using the recommended GWT approach of building parts of our application in an MVP manner. The logic we use is based on Google's examples - the Presenter fetches/prepares data and sets it on the View, and the View contains a reference to the Presenter which it calls (e.g. in UiHandlers).
Some parts of the application which we built should be reused in other views. For example - a view which is sometimes the "main view" of a part of the application - can be used inside a pop-up in another part of the application (of course, the views/presenters are initialized differently in this other case, but basically it is the same thing).
What would be the correct approach to do stuff like this? I cannot seem to find a suitable one without resorting to ugly hacky stuff.
For example - if I put the presenter of the reused component inside the main view - it is easy to initialize the reused component, but it is ugly to receive a result back in the main presenter. This can be solved by passing a runnable or creating a custom handler or passing the parent presenter itself to the reused presenter.
All of these approaches don't seem right to me though and seem ugly.
Any ideas/experiences?
What you're describing is a view being able to be controlled by 2 distinct presenters. Abstracting those presenters behind a common API, in the form of an interface, should be enough.
You can also see it as a composite widget being used within two distinct views. The composite widget would then expose events and a public API that both views could wire to their specific presenters.
See Activites and Places,It can help you to desing and structure you app.
https://developers.google.com/web-toolkit/doc/latest/DevGuideMvpActivitiesAndPlaces
.
We use MVP with custom EventBus to navigate across the views. One of our GWT module loads an ebook within a view. We have a button named "Expand", which upon clicked, loads the ebook in expanded mode thereby hiding the header, footer, etc.
Let us say the view (UiBinder) with "Expand" button is named as "ShowEbookView". Upon clicking "Expand" button, the ClickEvent is captured and fired to the EventBus. The logic onExpand(final ExpandEvent expandEvent) is written in the same "ShowExpandedMod" class.
Everything is okay, but we have a button named "Popout" in the expanded mode, which when clicked, should open the Ebook in a NEW page! We need to abstract the "ShowExpandedMod" class so that it can operate with the EbookId and can be used in the new page.
We have created a new Module with EntryPoint class, HTML page and UiBinder page for this new popout window. I am not sure how to proceed now with the abstraction and to use EventBus across different modules to load the same content ... (with re-usability ofcourse)
I've explained to my best, but perhaps not very clear! Please let me know if you want more details.
Thanks!
When you open a new window in browser you basically get a new instance of your GWT app. You can not use EventBus across different browser windows, i.e. across different GWT module instances.
What you can do is:
Add an argument to the Popout page URL. This is easies done via "history tokens" (fragment identifiers), like this http://yourdomain.com/popout.html#theIdOfTheDocument. Then you can retrieve the token via History.getToken()
Use DOM to communicate between browser windows: window.open() in javascript opens a new window and returns a reference to DOM of the new window. You can then access properties and functions of the new window. This is all javascript, in order to make this work in GWT you'll need to wrap it in JSNI.
Try and use MVP4G, in specific - take a look at their multi-modules feature (which utilizes GWT's code splitting capabilities).
This should make things like multiple EventBus's and cross-module event triggers a lot easier to handle.
Lets say that on all my views, or generally at any time in my app, I want to be able to show an error message popup, and it always looks the same. How do I do that?
First thought is having all my view models extend a base view model which facilitates these things, but after that, do I have this base view model actually create the UI widgets and display them?
thanks,
Mark
If you've got some common functionality that you want to provide across a range of views, then you can implement a base class that inherits from the PhoneApplicationPage, and then derive all your classes from that class instead. The XAML for your pages then looks like this:
<local:BasePage xmlns ...
xmlns:local="clr-namespace:MyNamespace"
x:Class="MyNamespace.MyPage">
However, you will not be able to define common UI components in the XAML for your base page. If you wanted to have common UI components you would have create them manually in the code-behind for the base page, perhaps in a handler for the Loaded event, but I think a better solution would be to provide your common UI in a UserControl, which you then add to each of your pages.
If you want to show a Toast or Message Box, then I would recommend the ToastRequestTrigger and MessageBoxRequestTrigger from the Silverlight Toolkit as described in the patterns & practices WP7 Developer Guide.
you could probably define an event on base view model, which is fired inside view model whenever an error occurs, then in view, you can subscribe to this event and display the popup. You can carry error context in EventArgs of the fired event.
Additionally you could unify the logic for displaying the popup but that's probably another story :)
This is testable and nicely decoupled from the view.
Hope this helps,
Robert
I'm a beginner with Eclipse RCP and I'm trying to build an application for myself to give it a go. I'm confused about how one actually goes about handling model objects. None of the examples I can find deal with the problem I'm having, so I suspect I'm going about it the wrong way.
Say I need to initialise the application with a class that holds authenticated user info. I used my WorkbenchWindowAdvisor (wrong place?) to perform some initialisation (e.g. authentication) to decide what view to show. Once that's done, a view is shown. Now, that view also needs access to the user info I had earlier retrieved/produced.
The question is, how is that view supposed to get that data? The view is wired up in the plugin.xml. I don't see any way I can give the data to the view. So I assume the view has to retrieve it somehow. But what's the proper place for it to retrieve it from? I thought of putting static variables in the IApplication implementation, but that felt wrong. Any advice or pointers much appreciated. Thanks.
The problem you are facing here is in my opinion not RCP related. Its more an architectural problem. Your view is wired with business logicand!
The solution can be done by two (common) design-patterns:
Model-View-Controler (MVC)
Model-View-Presenter (MVP)
You can find plenty information about this in the web. I am going to point a possible solution for your particular problem using MVP.
You will need to create several projects. One is of course an RCP plugin, lets call it rcp.view. Now you create another one, which doesnt make UI contributions (only org.eclipse.core.runtime to start with) and call it rcp.presenter. To simplify things, this plugin will also be the model for now.
Next steps:
Add the rcp.presenter to the
dependencies of rcp.view (its
important that the presenter has no
reference to the view)
Export all packages that you are
going to create in the rcp.presenter
so they are visible
In rcp.presenter create an interface
IPerspective that has some methods
like (showLogiDialog(), showAdministratorViews(User user), showStandardViews(User user))
Create a class PerspectivePresenter that takes IPerspective in the constructor and saves it in an attribute
In rcp.view go to your Perspective, implement your interface IPerspective, and in the constructor create a new reference presenter = new PerspectivePresenter(this)
call presenter.load() and implenent
this in the presenter maybe like this
code:
public void load()
{
User user = view.showLoginDialog(); // returns a user with the provided name/pw
user.login(); // login to system/database
if(user.isAdministrator())
view.showAdministratorViews(user);
else
view.showStandardViews(user);
}
As you can see, the view just creates a reference to the presenter, which is responsible for all the business logic, and the presenter tells the view what to display. So in your Perspective you implement those interface functions and in each one you can set up your Perspective in a different way.
For each View it goes in the same way, you will need a presenter for the view which performs operations and tells the view (using the interface) what to display and passing down the final data. The view doesnt care about the logic. This is also very usefull when using JFace-Databindings (then only bound data is passed to the view).
For example, the WorkbenchWindowAdisor will just create everything that is needed in the application. Other views, perspectives, then can enable/disable menus and so on depending on the data they got (like when isAdministrator you might want to enable an special adminMenu).
I know this is quite a heavy approach, but the Eclipse RCP is designed for big (as the name says rich) applications. So you should spend some time in the right architecture. My first RCP app was like you described...I never knew where to store things and how to handle all the references. At my work I learned about MVP (and I am still learning). It takes a while to understand the concept but its worth it.
You might want to look at my second post at this question to get another idea on how you could structure your plugins.