Xamarin Cross Platform Development Cookbook Download 13
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Cross-platform mobile development enables companies to develop one single application that runs on multiple platforms, such as Android and iPhone. Using web-based languages is one way to accomplish this goal. This talk covers developing a Mobile course using the React JavaScript Library for cross-platform apps. React JavaScript apps have imperative, declarative, functional, object oriented, markup, and scripting language features. Although React is a JavaScript library, it has its own compiler that enables syntax extensions. The talk includes discussions of approaches for teaching about React's unique features such as: (1) Classes and functions that are render-able components, with a mixture of HTML, CSS, and React's JavaScript extensions, (2) a new syntax for Document Object Model event handling with functional programming behavior, (3) differences between modifiable state ("state") and non-modifiable state ("properties") for a component, and (4) asynchronous data storage and access. Course content could also potentially be used to illustrate concepts for Programming Languages and Operating Systems courses.
In this article by George Taskos, the author of the book, Xamarin Cross Platform Development Cookbook, we will discuss a cross-platform solution with Xamarin.Forms and MVVM architecture. Creating a cross-platform solution correctly requires a lot of things to be taken under consideration. In this article, we will quickly provide you with a starter MVVM architecture showing data retrieved over the network in a ListView control.
Xamarin.Forms is a great cross-platform UI framework that you can use to describe your user interface code declaratives in XAML, and it will be translated into the equivalent native views and pages with the ability of customizing each native application layer.
Xamarin.Forms and MVVM are made for each other; the pattern fits naturally into the design of native cross-platform mobile applications and abstracts the view from the data easy using the built-in data-binding mechanism.
Since the release of .NET 5, Microsoft has been trying to unify different .NET implementations into one .NET release. .NET Multi-platform App UI (or .NET MAUI) is an effort to provide a unified cross-platform UI framework. We will learn how to use .NET MAUI to develop cross-platform applications in this book.
Technologies used in web application development and backend services development are not platform-specific and can be used on different platforms as they are. When we talk about cross-platform development, we usually refer to native application development. In native application development, cross-platform development technologies can help to reduce costs and improve efficiency. The most popular cross-platform development technologies in this category include Flutter, .NET MAUI/Xamarin, and React Native. Table 1.1 provides an overview of available cross-platform technologies and alternative solutions from Microsoft. The technologies listed here are not exhaustive. I just want to give you a feeling of what kind of technologies exist in each category and what Microsoft solution can be used as an alternative.
There is no best choice of cross-platform tool or framework. The final choice is usually decided according to business requirements. However, from the preceding table, we can see that the .NET ecosystem provides a full spectrum of tools for your requirements. The development team for a large system usually requires people with experience in different programming languages and frameworks. With .NET, the complexity of programming languages and frameworks can be dramatically simplified.
Java is developed as a language with the goal to write once and run anywhere. It is built around the Java programming language and the Java Virtual Machine (JVM). The JVM is a mechanism to run on supported platforms that helps to remove platform dependency for developers. With this cross-platform capability, Java becomes a common choice for cross-platform applications and services development.
While there are multiple languages that use the JVM as the abstraction layer for cross-platform capability, the interoperation between Java-derived languages is not at the same level as .NET languages. All .NET languages are built on one architecture and share the same BCL, while Java languages, such as Java, Kotlin, or Scala, are developed separately for very different purposes.
At the same time, Mono projects went through many changes as well. At the time that Mono was owned by the Xamarin company, Xamarin developed the Xamarin platform based on Mono to support the .NET platform on Android, iOS, Universal Windows Platform (UWP), and macOS. In 2016, Microsoft acquired Xamarin, which became the cross-platform solution in the .NET ecosystem.
Before the acquisition of Xamarin, Microsoft has already started work to make .NET a cross-platform framework. The first attempt was the release of .NET Core 1.0 in 2016. .NET Core is a free and open source framework, available for Windows, Linux, and macOS. It can be used to create modern web apps, microservices, libraries, and console applications. Since .NET Core applications can run on Linux, we can build microservices using containers and cloud infrastructure.
As we mentioned in an earlier section, Xamarin was part of the Mono project and was an effort to support .NET on Android, iOS, and macOS. Xamarin.Forms is a cross-platform UI framework from Xamarin. .NET MAUI is an evolution of Xamarin.Forms. Before we discuss .NET MAUI and Xamarin.Forms, let us review the following diagram of Xamarin implementation on various platforms.
Xamarin.Android, Xamarin.iOS, and Xamarin.Mac provide a .NET environment that exposes almost the entire original SDK capability on their respective platforms. For example, as a developer, you have almost the same capability with Xamarin.Android as you do with the original Android SDK. To further improve code sharing, an open source UI framework, Xamarin.Forms, was created. Xamarin.Forms includes a collection of cross-platform user interface components. The user interface design can be implemented using the XAML markup language, which is similar to Windows user interface design in WinUI or WPF.
Since Xamarin exposes the capability of the underlying platform SDKs, you can access device features using the .NET API. However, the implementation is platform-specific. For example, when you use a location service on Android or iOS, the .NET API can be different. To further improve code sharing across platforms, Xamarin.Essentials can be used to access native device features. Xamarin.Essentials provides a unified .NET interface for native device features. If you use Xamarin.Essentials instead of native APIs, your code can be reused across platforms.
Using Xamarin.Forms together with Xamarin.Essentials, most implementations, including business logic, user interface design, and some level of device-specific features, can be shared across platforms.
Most modern application development on various platforms uses the Model-View-Controller (MVC) design pattern. To separate the business logic and user interface design, there are different approaches used on Android, iOS/macOS, and Windows. On all the platforms involved, even though the programming languages used are different, they all use XML-based markup language to design user interfaces.
Even though we can share almost all UI code with Xamarin.Forms, we still need to handle most of the resources used by an application in each platform individually. These resources could be images, fonts, or strings. In the project structure of Xamarin.Forms, we have a common .NET standard project and multiple platform-specific projects. Most of the development work will be done in the common project, but the resources are still handled in the platform-specific projects separately.
From Figure 1.2, we can see that there is a common BCL for all supported operating systems. Under the BCL, there are two runtimes, WinRT and the Mono Runtime, according to the platform. For each platform, there is a dedicated .NET implementation to provide full support for native application development.
In Table 1.4, where we compared the user interface design options on different platforms, we mentioned that there is another way to design cross-platform user interfaces in .NET MAUI, which is Blazor.
Released in ASP.NET Core 3.0, Blazor is a framework for building an interactive client-side web UI with .NET. With .NET MAUI and Blazor, we can build cross-platform apps in the form of Blazor Hybrid apps. This way, the boundary between a native application and a web application becomes blurred. .NET MAUI Blazor Hybrid apps enable Blazor components to be integrated with native platform features and UI controls. The Blazor components have full access to the native capabilities of a device.
After launching Visual Studio Installer, we will see a screen similar to the one shown in Figure 1.3. Please select .NET Multi-platform App UI development and .NET desktop development in the list of options. We also need to select ASP.NET and web development for the .NET MAUI Blazor app, which will be covered in Part 2 of this book.
I published an app, PassXYZ.Vault, developed using Xamarin.Forms and KPCLib in app stores. In this book, we will rewrite PassXYZ.Vault together, using .NET MAUI. You can learn about cross-platform programming through the progressive development of this app until it is published in app stores.
In this chapter, we started with an overview of cross-platform technologies. We compared a .NET solution with other cross-platform technologies. After that, we went through the .NET landscape. I explained the relationship between .NET Framework, Mono, and .NET Core. Then, we discussed Xamarin and .NET MAUI. We reviewed the difference between Xamarin.Forms and .NET MAUI. One important feature in .NET MAUI is that we can use Blazor together with XAML user interface design. Then, we had an overview of .NET MAUI Blazor. Finally, we set up a development environment for the rest of the chapters.
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