Xamarin Tutorial (Part 1): Create a Blank App
In a recent post to software decision makers, I discussed reasons businesses should consider cross-platform native development over website development. You can read the previous Xamarin Tutorial post here.
In the post, I gave a case to use the Xamarin toolset, why it should be considered, and why it could be a good business and development decision for your organization.
In this Xamarin Tutorial series, I will be building a solution that can be used as a starting point for cross-platform applications using the Xamarin toolset. Today I will be focusing on the following:
- What is Xamarin?
- How to Setup the Xamarin development environment using Microsoft Visual Studio
- Briefly talk about iOS support
- Discuss Shared vs Portable Class Libraries (PCL) strategies and how to use both
- Connecting to your Mac to debug an iOS version of your application
- Using the Visual Studio iOS Simulator to debug your iOS application
Xamarin – What is it?
Before we start diving into creating our solution, I will include a snippet from the post mentioned above that gives you an overview of Xamarin. After this explanation, my assumption will be that you at least know what it is and why we are using it.
Xamarin is a Microsoft owned company that started with the engineers that created the popular Mono, Mono for Android and MonoTouch, which are cross platform implementations of the Common Language Infrastructure (CLI) and the Common Language Specifications, also known as .NET.
Xamarin uses a shared C#/.NET codebase along with either Xamarin Studio or Visual Studio, to write native Android, iOS, and Windows Apps. Did you understand that? Yes, native applications. Wow, so, all your code is 100% shared. Again, not exactly. But, close.
For most simple UI patterns, Xamarin.Forms allows you build native user interfaces for iOS, Android and Windows using 100% shared C#. It also includes dozens of controls and layouts which are mapped to native controls in their respective platform.
Depending on your application needs, however, you may need to access a platform specific feature, such as Live Tiles for Windows, or maybe you need to create a custom control that isn’t a native control for any of the platforms. In these scenarios, Xamarin provides a means to call into platform specific code. However, check this out, … wait for it … wait for it … it is still in C#.
So, as you can see, the App Logic and most of the user interface code is shared across all platforms. In fact, there is even a community of user-built components that you can leverage in your application using both NuGet and the Xamarin Component Store.
Development Environment – The Microsoft Way
Now that we have the basic definition and understanding of what Xamarin is, we can put that behind us and make sure that we have the tools necessary to start developing. For this, my plan is to stick with as many Microsoft technologies as possible.
So, first in this Xamarin Tutorial, I am going to assume that you are using Windows 10 and have a flavor of Visual Studio 2015 installed on your machine. Even under that assumption, we need to make sure that you have the Xamarin tools installed. Luckily, this is easy.
First, make sure that you don’t have any instances of Visual Studio currently running.
Next, open your Windows Settings application and type add or remove in the search box. Select Add or remove programs from the dropdown list.
You will be taken to the Apps and Features section of settings. Scroll down and select Microsoft Visual Studio 2015. Now select Modify.
You will be prompted to give permission to the installer. Give it permission by selecting Yes. You should see the Installation program initializing.
If you didn’t shutdown Visual Studio 2015 before you selected Modify, the installer will notify you and recommend that you close Visual Studio now. If you did forget to close Visual Studio or skipped that step entirely, close Visual Studio now and select Retry.
If Visual Studio is closed, the installer should provide you an option to modify the current installation. Select Modify.
After selecting Modify, you will see a list of all the features currently installed. Since our goal in this Xamarin Tutorial series is to create a cross platform application, verify that all the Cross Platform Mobile Development features are enabled. We aren’t going to use all of features, but if you know you are going to do cross platform development and you have the space, install it now and forget it, you will have all the tools necessary for the future.
Since I already have the features installed, I can be assured that all the necessary tools are installed for me to start developing cross platform applications. If some of the features weren’t enabled for you, make sure they are and select Update. This will install all the tools for you.
If we plan on having iOS support for our application, Xamarin.Forms does support it. So, yes, you can create iOS applications on Windows using C#.NET. However, you will need a networked Mac running OS X Yosemite (10.10) & above with XCode 7 installed. You will also need to install the Xamarin.iOS tools onto the Mac. The best way to do this is to use the Xamarin Unified Installer, which will install everything you need. You can view these instructions here.
I will assume that you have XCode and the Xamarin.iOS tools setup on your Mac. However, I will discuss how to attach to your Mac, build and run/debug the application later in the post.
One thing we can do right now is setup the permissions to allow us to debug our application on the iOS simulator on the Mac.
First, on your Mac, search for Remote Login in Spotlight.
Select Sharing. Select Remote Login and make sure that your account is in the list of Allow Access for: Only these users. I am an Administrator on my Mac, so I will just allow all Administrators.
NOTE: You could allow All Users to have remote access, but, I am not sure that is a good idea.
Your Mac should now be discoverable in Visual Studio. Again, we will talk more about this later.
Create a New Project
Now we can create our new project. Open Visual Studio, select File, New, Project…
Next, select Installed, Templates, Visual C#, Cross-Platform. Then, select Cross Platform App (Xamarin.Forms or Native). Enter the name of your project. Make sure the directory is correct and then select OK.
Another dialog prompting for the type of cross-platform project will be displayed. Select Blank App, Xamarin.Forms, Shared Project and then select OK.
Visual Studio will start creating your Xamarin solution. However, since we are targeting Universal Windows Platform applications in our project, you will be prompted for your Target and Minimum versions of Windows. I have chosen to target Windows 10 Anniversary Edition with a Minimum version of Windows 10 (Build 10586). Once you have made your selection, select OK.
You will also probably see the following dialog while it is creating the solution.
When it is finished, you should notice that there are several projects in your solution. One for each of the platforms we will target with our application.
Along with the iOS, Android and UWP projects, you should also notice that there is a Shared project. I know, I kind of blew past that part when I had you select the Code Sharing Strategy shared project. I did this on purpose, I will explain this in more detail now.
Xamarin uses a couple of strategies for sharing code within our Xamarin solution: Shared and Portable Class Library (PCL).
The shared strategy basically takes each file in the shared project and compiles it under each of the other projects. Think of it as making a copy of the files in the shared project into each specific platform project and then doing a build. You can still do platform specific code in the shared project by using #if compiler directives, but be cautious, your code can, and probably will, become ugly fast.
Note: the shared project isn’t really a traditional project that gets built into an assembly. You can’t actually build it.
Portable Class Libraries (PCL)
With portable class libraries, the code is compiled separately and referenced in each project like any normal class library. The big difference here is that you have access to a subset of .NET that is compatible with all the target platforms. So, for example, you could use System.Net.Http, but trying to access hardware, such as, the camera API is not available. You could, however, use a generalized interface that uses dependency injection.
Both Shared and Portable?
So, as you can see, each strategy mentioned above, contains some pros and cons. So, it really depends on the type of application and how much external sharing you are going to need to do with the code. Simply put, if you are going to share code outside of the application itself, PCL’s are a good choice. However, if this is a one-time application with no externally shared code, the shared strategy would be a good choice.
That being stated, what if we want to use both? Can we do that? To answer your question, yes. What if you have a lot of shared code between applications, but you also have a significant amount that is just shared across your specific application?
In fact, let’s add a PCL to our project for any code that we might want to share with other applications we write in the future. We won’t do anything with it right now other than wire it up for use in my next blog post.
First, right-click on the solution, select Add and then select New Project…
From here, we want to repeat the same steps we used to create the solution, but in this case, we want to select a class library. Select Installed, Cross-Platform, Class Library (Xamarin.Forms). Enter the name of your shared class and select OK.
Okay, now, one thing you should know is, by default, the project will add a Xamarin ContentPage, XamarinBlog.CommonServices.cs. You can go ahead and delete it now.
Okay, we now have a portable class library in our solution, however, it isn’t being referenced. So, go ahead and reference it in each of the platform specific projects by right clicking on references and selecting Add Reference…
Select Projects, then Solution, then select your new PCL from the list. Finally, select OK.
Okay, now that we have our PCL referenced in each project, you should be able to build most of the projects. As far as the iOS project, we really haven’t talked about how to connect to your Mac for building, so let’s do that quickly.
Connecting to the Mac
For us to build our iOS project, we will need to connect your Visual Studio iOS project to a Mac. To do this for the first time, all you do is attempt to build the project. Right-click on the project and select Build. If you haven’t connected before, Visual Studio will display instructions for setting up the remote login functionality on your Mac. Since we already did this earlier in the post, we will skip them and select Next. If you would like, you can turn off the instructions for next time, however, if you are like me, I forget the “setup once and forget” things, so I usually leave mine unchecked.
You will now be prompted to pick your Mac. For it to show up in the list, you must have setup remote access properly and the Mac bust be on the same network as Visual Studio. Select your Mac and then select Connect.
Next, you will be prompted for your username and password. Enter your credentials and select Login.
Once you have selected Login, it will attempt to connect to your Mac. If it is successful, you will see a link under the Icon for the machine you selected. Once you see this, select Close.
Now, go ahead and try to build. I should build successfully if everything on your Mac is setup correctly.
Can I see Something?
I know, we have done a lot up to this point and we haven’t seen a darn thing. Well, before we run the application, I do want to mention a couple more things. First, let’s look at where this whole application starts in code. Where is the application object for this thing?
In the shared project, XamarinBlog, open App.xaml.cs.
Notice this is where our Application object for all our projects resides. How do we know what page to load first? Check out the constructor. Notice that we assign XamarinBlog.MainPage to the MainPage property of our application. Also, you may have noticed that there are a number of events that are created for us: OnStart(), OnSleep() and OnResume(). These are application lifecycle events that get fired for each platform. We will probably talk more about these in later posts in this series.
Let’s look at the XamarinBlog.MainPage object in Mainpage.xaml and see if we can figure out what this page is going to be presenting us. Select MainPage.xaml.
Looking at the markup, we see we are creating a ContentPage with a label, that has the text ‘Welcome to Xamarin Forms!”, and it is centered in the middle of the page.
Now that we know what it is supposed to do, let’s see it in action. Build and run the application for each platform and see what you get. It should look something like the following:
Cool, right? Three platforms, mostly the same code. Well at least the UI, so far.
Using Visual Studio iOS Simulator
It is nice to be able to debug on your Mac, but I must admit, it is kind of a pain at times to be forced to sit by the machine to test your application. Well, a cool new feature for Visual Studio is the Visual Studio iOS Simulator. This add-in for Visual Studio allows us to debug our iOS version of the app right on our computer. So, you don’t need to be near your Mac to do the debugging. You can do it right on your PC.
To get the add-in, download the installer here. You might have to restart Visual Studio for changes to take effect. Once you do, make sure that you select iPhoneSimulator and run the application again.
You should see the Visual Studio iOS Simulator with your application.
If for some reason, you would like to disable the Visual Studio add-in and go back to debugging your iOS application on the Mac you can do so. All you need to do is select Tools from the main menu and then select Options…
Scroll down to the Xamarin tab and select iOS Settings. Uncheck the Remote Simulator to Windows checkbox and select OK.
Now, you should be able to debug on your Mac again.
So, to summarize what we learned in the first part of our Xamarin Tutorial series:
- We answered the question, “What is Xamarin?”
- We Setup the development environment using Microsoft Visual Studio
- Briefly talked about iOS support in Xamarin and Visual Studio
- Pointed out the differences between the Shared and Portable Class Libraries (PCL) strategies and how to use both
- Demonstrated how to connect to your Mac to debug the iOS version of your application
- Installed Visual Studio iOS Simulator and ran our iOS application on our PC
In Part 2 of this Xamarin Tutorial series, we will talk about implementing the Model-View-ViewModel pattern using the MVVM Light Toolkit to maintain a solid separation of concerns. So, stop back and continue your journey with me on developing cross-platform applications using Xamarin.
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