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Xamarin Forms Hybrid Apps

Posted by at 28 May 2018 in Article

 Why Hybrid Apps?

This has always been a common approach if you do Cordova or PhoneGap and it should do a great job for simple apps that doesn't rely too much platform specific feature, The question is why should we do it in Xamarin? Or what scenario would persuade us to use hybrid approach? My early days with Xamarin development, That time where there were no reliable Charting library available yet, My team were force to use other alternative and so we decided to use webview with the help of Xlab's HybridWebview library and highcharts javascript library we were able to satisfy our customers need. Be aware that Xlabs project is no longer maintained. It may NOT work with newer versions of Xamarin.Forms. Though it has done a great job i am not recommending it for use because its somewhat bloated, things that we are not gonna need. Fortunately for us i have found this lightweight HybridWebview library thanks to Ryan Dixon. Now we should be able to do Hybrid apps, Later we will discuss how to setup our web files per each platform, I will provide two examples, First is we will gonna use Highcharts and second we will gonna use Pignoise calendar. This libraries along with hybridwebview is a better alternative if you cannot afford a pricey libraries from known component vendors (you know them), Though they have done a great job in bringing this native component it is of course your choice.

Creating Your Xamarin.Forms project

Very straightforward just a create a xamarin project and you should be able to create three platforms project atleast and one PCL project. Then you must install Webview nuget package by Ryan Dixon this is a very lightweight library, Make sure to install it on all platforms. In our case we used TabbedPage to showcase each javascript library.

Setup Your Highcharts and Calendar page

Now to setup your highcharts library, keep in mind that the file structures differs per each platform, For Android project, all your html, styles and javascript file must be placed under Assets folder while in iOS project it should be placed under Resources folder and For UWP or WindowsPhone project must be under its root. You can take a look how it should be structured per platform.




Communicate Your Web Page to Backend

If you want to know the details how the communication between your page and your Backend explains so much in this documentation. First thing you should do is to register a callback using RegisterLocalCallBack method (the complete documentation and source code can be found here). In our case we use the calendar selectdate method(to call backend method). Register a callback something like this in You Xamarin Code:
CalendarWebView.RegisterLocalCallback("selectdate", (str) =>
DisplayAlert("Selected Date", str, "OK");
Now in your html page you can call a method like this to invoke the callback from Xamarin Code
csharp("{'action': 'selectdate', 'data': '" + text +"'}");
view raw CallXamarinCode.js hosted with ❤ by GitHub

Additional Note

Here is the minimal reason in my case that if we do hybrid we should do it in Xamarin.Forms rather than Cordova.
  • It’s performant; it compiles down to native.
  • Implements most logic in C# with minimal amounts of native code specific to Android or iOS.
  • You can use most javascript libraries like Jquery, Ember and AngularJs

Wrapping Up

Doing native is not always the silver bullet, there were times we need to do simple stuff to accomplish the needed business needs. But Xamarin.Forms can always do both if it needs to. I hope this article have helped you. If you want the full sample source you can check it right here LINK.
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Tags: Xamarin Forms Hybrid Apps

Xamarin Forms Validation the easy way

Posted by at 28 May 2018 in Article

Actually there is no easy way (forgive me), but this article will help you the right way of doing it. The main reason why we need an input validation is to ensure a right data will be entered in to our app and it also provide extra protection because it enforces business rule that no garbage data will be going into the system. First you need to understand the basics of Behaviors,  it lets you add functionality to your UI controls without having to subclass them, a function like validating input, controlling animation, adding effects and triggering commands and making it reusable component,  In our case we will gonna use it to provide validation for our inputs. If you want to get started and get to know more about Behaviors you can start in this LINK. Then we also need to add Triggers in our arsenal, Triggers allow your UI element to respond to any property changes in pure xaml (Yes you read it right), We will provide a sample later and dissect how Behaviors and triggers all work together to obtain our goal.


The Behaviors and Triggers are the components that can be made reusable across your app which makes validation and animation a breeze. This will also reduce backends extra checking and "if-else" (f*cking old fashion way).

Creating Your Xamarin.Forms project 

Now let us create our new project and name it "ValidationApp", you should be able to create three platforms project and atleast  one PCL project. We will reuse the default page and create a similar UI like the one below. we will make sure thats our xamarin.forms library are up to date by updating our nuget packages. Select the Portable Class Library

Dissecting Behavior 

Behaviors is very much like our C# Extension methods but for xaml elements. Now lets methodically cut up a part of Behavior and study how it make sense. In this case i already created a Generic Behaviorbase. Now lets make a simple Behavior which will validate an empty text, Let's name it "EntryValidatorBehavior". It should look like the one below.   Now let us expose a bindable property which will notify our xaml element that the entry is valid, In Our case we will named it "IsValid, it should look like this: The last but not the least let us subscribe to Entry's TextChanged event to listen when the user has entered a new value. We need to override two methods from a behavior namely "OnAttachedTo" and "OnDetachingFrom" and add a subscribe and unsubscribe to TextChanged event respectively. What you see is a complete version of our EntryValidatorBehavior.

Awesome! Let's see it in Action 

You just have created a "REUSABLE" component which can be used across your app UI "congratulations". Now, Let us use the default page "MainPage" to test our EntryValidatorBehavior, For simplicity sake we will only create one entry and one button, like the one below. Our objective to make the user input a non-empty code before submitting it, In our case we will disable a button until he inputs a non-empty code.

Dissecting our XAML Code 

This is our XAML Code, i did make it simple as much as possible so we could get  a grasp of it. If you take a look of it it has one Entry and one Button, Everytime the user changes the value of the entry it will change the state of "IsValid" property in which will invoke  triggers which has a binding to its property. Awesome, now lets try to run our app and see it in action. I you have run the app you will notice that when the entry's value is blank will disable the button or it will enable when the entry has non-empty value.

More Awesome Validation

I have provided a sample code here in this LINK. And i also added a more awesome validation which contain visual indicator that will notify user of the validation message.

Wrapping Up

Creating maintenable and reusable components is breeze when you will follow this patterns, And as your app is getting more complex you will appreciate the awesomeness of this patterns and leave you concentrating on the more important business aspects on your application. If you want more and advance topic you can catch us at this facebook groups  MondPH And Xamdavao.  If you want the full sample source you can check it right here LINK.
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Tags: Xamarin Forms Validation the easy way

Creating Draggable Sliding Up Panel in Xamarin Forms

Posted by at 28 May 2018 in Article

There were library provides a simple way to add a draggable sliding up panel (popularized by Google Music and Google Maps) to your Android application, But implementing across all platforms requires a couple of custom rendering and abstraction. Below are the popular apps that has draggable sliding up panel. Google Maps Umano

Creating Draggable Sliding Up Panel

Now lets start creating our own draggable sliding up panel in PURE xaml, No need to implement custom renderer or create bindings to an existing Android or iOS libraries (How is that possible?). Its simple we will just gonna need to subscribe to PanGestureRecognizer to the UI element in our case the bottom menu. [Below is the finish product.]

Creating Your Xamarin.Forms project 

Now let us create our new project and name it "SlidingUpPanel", you should be able to create three platforms project and atleast  one PCL project in my case i was created it in Visual Studio 2017 and im using Prism and Autofac.

The Secret in UI magic 

This is basically the classic tricks that we have done before in the previous project like "Custom Popup" you can read in this link. So first we have to wrap our content UI Elements around a GridLayout. Now inside the GridLayout we will add a StackLayout and we will gonna name it as "QuickMenuPullLayout" this will be the container of the draggable UI (handle). Now that we have completed the UI elements this time we will gonna wire up the animation in the backend code, we will gonna need extra help of one library that will gonna manage the subscription of events and to avoid memory leaked, We will gonna use Reactive Extension.

Wiring Up 

Just i have said earlier we will gonna need to subscribe to PanGestureRecognizer to the UI element in which is the bottom menu. with the help of the Reactive Extension we end up make it fluid and beautiful. With the help of PanGestureRecognizer we were able to update the UI element and make it draggable. We can also make the element not go beyond the specified bounds using Math.Max and Math.Min please the sample code below.

Awesome! Let's see it in Action 

Below is the finished product, I hope it will help you to the journey of Xamarin.Form mobile Development. If you want the source code please browse in this link here.

Wrapping Up

Creating Xamarin.forms Application should be a breeze with a tricks that have proven over time, And Xamarin is getting improved all this time and we should utilized it. If you want more and advance topic you can catch us at this facebook groups  MondPH And Xamdavao.  If you want the full sample source you can check it right here LINK. enjoy coding.
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Tags: Creating Draggable Sliding Up Panel in Xamarin Forms