We have a xamarin forms app using the MVVM pattern. We have repeated UI logic that gets run whenever any contentView is loaded in the application and just wondering where the best place for this will go. Currently in our legacy application it is written in every control which is incredibly frustrating since if it needs fixing then it needs to be fixed in every separate location. What is the best approach for this type of code.
An example of what I mean is that on initialise of every contentView it runs through security privileges of the current user and hides or shows UI controls on that ContentView depending on what the user is allowed to see. This occurs on every form in the system. This is a simple example but there is plenty.
Any ideas?
Why not put it in a parent class? Derive from ContentView, then have all your relevant controls derive from that. You can do this with pages too. All pages in my latest Xamarin Forms app derive from this:
public abstract class BaseContentPage<T> : ContentPage, IViewFor<T> where T : class, IViewModel
Related
I am following a tutorial video on how to allow users to edit their profile. In this tutorial, they are using storyboards and I am not. I was wondering, do I have to use storyboards in order to follow along? Or can I use their code to plug into mine without the storyboard?
According to Apple documentation:
A storyboard is a visual representation of the user interface of an
iOS application, showing screens of content and the connections
between those screens. A storyboard is composed of a sequence of
scenes, each of which represents a view controller and its views;
scenes are connected by segue objects, which represent a transition
between two view controllers.
As you are probably guessing, storyboards contain information about widgets, animations, views that are required by the code you will be adding to yours. Additionally, Storyboards also contain the connection between the visual elements and the code (outlets and actions). All of that can be created programmatically but the code you will be pasting from this tutorial, if it's coming from a project that includes storyboards, won't contain this associated logic.
So, at this point, it would seem highly unwise to add complexity to your tutorial to recreate these elements at once. What I would suggest is for you to follow the tutorial and then try to remove some of these elements and replace them by code to obtain similar results just as an exercise to learn. Keep in mind that Storyboards have been around to simplify the design of UI in the application, so I would recommend for you to master their usage instead of shying away from them.
I’m working on an application for Android and iOS, which requires a certain flexibility for one or two views. That’s why we created & implemented a service that translated a basic list of objects into a user interface for both iOS & Android. But now that Xamarin.Forms is released, we decided to replace our service by the one Xamarin provides. I did succeed in creating the views with Xamarin.Forms, resulting in better looking & smoother running pages. But my problem lies in the navigation of it. Here is a little drawing on what I would like to achieve:
I would like my app to start an activity that starts with a custom fragment. After clicking a button on this fragment, I would like the page I created with the Xamarin.Forms api to be added to my current navigation stack! Once the user is finished with the Xamarin.Forms page, it navigates to a second custom fragment, all that without breaking the navigation cycle. Does anybody have an idea on how I can achieve this?
For the iOS developpers: replace Activity with NavigationController & Fragment with ViewController
Take a look at CarouselPage for Xamarin.Forms' own approach. It doesn't look like that's what you need but you can also look at its source code and maybe make a custom renderer yourself.
You may also want to take a look at MVVM
As for the easier/hackier way you'd want to make a button on each page and when the button is tapped execute Navigation.PushModalAsync(nextPage) - there won't be a "< Back" button any more, you may need to implement that yourself if you need it.
If by your meaning of 'current navigation stack' is for using the native Navigation of each platform, then remember that you don't have to use Xamarin.Forms' Navigation Model and functions such like PushAsync.
If you prefer to do Navigation with code specific to each platform then you can do this the same as normal. Just create your stub pages in each platform specific project and set the Xamarin.Forms content for each page from the shared project.
From each platform specific stub page (Activity / UIView / PhoneApplicationPage) you could then execute an Action<> call setting on the shared Xamarin.Forms page to help with the navigation, or alternatively, hook into a custom-event that is raised from the Xamarin.Forms** page back to the platform specific stub page to allow you to do navigation from there.
Like Sten mentioned there won't be any 'Back' button so you will most likely have to do that yourself.
I was playing with Xamarin Mobile api MediaPicker which uses MediaRecorder with monodroid to make a plugin to record a video.
Android must preview the video inside a VideoView. This restriction applies to wp7 and ios too for privacy.
So, I need to get the VideoView (or Rectangle in wp7) from my custom view and setPreviewDisplay to this VideoView in my plugin (or init MediaPicker with this VideoView).
What is the best way to implement my portable plugin which requires UI element ?
Thanks in advance for your help.
What is the best way to implement my portable plugin which requires UI element ?
I guess my first question is "do you need a portable plugin?"
What is the interface that you actually need at the ViewModel layer or lower?
My guess is that the cross-platform interface that the ViewModel will see might contain just:
some control commands (things like start/stop)
some summary information - e.g. video length
a file access layer - this may be as little as a file path?
If that's the case, then I'd probably implement most of the logic within Controls/Views/UIViews in the UIs, and would then bind the relevant commands and values to those ViewModel properties.
So I wouldn't personally implement this as a plugin at all!
I've previously done a couple of apps which use video views - one for video capture (Android only), one for bar code scanning.
I found that the basic available samples worked quite well. However, once I started trying to extend them, then they became quickly fragile, they were hard to get working and they were quite frustrating to develop!
I would genuinely recommend starting your current develop as UI View code. After you've got it working, then you might find a nice way to split up the control and interface into a plugin - but I suspect that this won't be where most of your time is spent.
e.g. for my next QR code app, I plan to use the separate UI controls in https://github.com/Redth/ZxingSharp.Mobile - at the ViewModel level, I can hopefully just expose some sort of Command which acts on the decoded QR strings.
I'm working on a Desktop JavaFX 2 application. We're using FXML, an MVC architecture to build a tabbed UI. Now I'm struggling to find an elegant way for this scenario:
User clicks button on View 1, which is in a tab on the Main View.
Controller creates a new model object.
New model object is shown through View 2, which is opened in another tab on the Main View.
Would it be suitable to implement a class similar to GWT's com.google.gwt.user.client.History, handling all navigation request. First I'd have to register the main view. Or am I overseeing a JavaFX mechanism?
I implemented a tabbed web browser with history management which sounds a bit similar to your situation. The code is a bit of a mess, but you could look through it if you like to see if there is anything worthwhile there which is applicable to your situation.
For the next release (2.2) of JavaFX there will be a generic pagination control (anybody can register at that link to view the issue) which will probably help encapsulate some of the functionality you require as it mentions TabPane like functionality.
There has also been some discussion of JavaFX history functionality on the open-jfx development mailing list.
The jfx-flow project was created to enable weblike interfaces (e.g. views with history navigation) on JavaFX. Not sure if it's completely developed for your use case, but you could take a look at that too.
I am new to windows phone (WP7) and to me it looks like everything on WP7 is about pages. I want a small window to pop up from the bottom of a page while staying on the same page. The small window will have some controls (like slider, list etc.). It should not behave like a modal dialog box though, i.e. the rest of the page (which is not covered by the small window) should still be active and user should be able to do something there. And I want to have a separate C# class which will handle the events from the controls on the small window.
This is very easy on iPhone, using view controllers, is there something similar on windows phone?
It sounds that it would make sense to make your "pop up" part of the page with the content it is intended to manipulate content on that page. If you want to encapsulate the functionality of the "pop up" you could make it a UserControl. If you went this route then animating it to slide onto the screen will be straightforward.
Windows Phone 7 typically uses an MVVM model compared to iPhone's MVC one for app structure. The direct comparison therefore isn't appropriate. WP7 also uses a very different design language to that of the iPhone and so a straight port of application design and layout is also unlikely to create a great experience on WP7.
I'd recommend taking some time to understanding the differences in the platforms and how your existing design would be best suited to recreation on WP7. Not only will this help you create a better experience on WP7 but enable to see if this your question actually relates to something you should be doing or not.
This very much sounds like something that goes against the nature of the platform, and the general design guidelines.
If you're providing some available configuration options to the user, you should do it on a separate page, so the user can change the settings there, approve it, and then be navigated back to the previous page.
However, if you really want to, you're talking about displaying a UserControl inside a Popup. But it wouldn't be a very good user experience, and confuse most users, as it doesn't follow the same look&feel as the rest of the platform.