Book Image

Mastering Xamarin.Forms

By : Ed Snider
Book Image

Mastering Xamarin.Forms

By: Ed Snider

Overview of this book

Discover how to extend and build upon the components of the Xamarin.Forms toolkit to develop an effective, robust mobile app architecture. Starting with an app built with the basics of the Xamarin.Forms toolkit, we’ll go step by step through several advanced topics to create a solution architecture rich with the benefits of good design patterns and best practices. We’ll start by introducing a core separation between the app’s user interface and the app’s business logic by applying the MVVM pattern and data binding. Discover how to extend and build upon the components of the Xamarin.Forms toolkit to develop an effective, robust mobile app architecture. Starting with an app built with the basics of the Xamarin.Forms toolkit, we’ll go step by step through several advanced topics to create a solution architecture rich with the benefits of good design patterns and best practices. We’ll start by introducing a core separation between the app’s user interface and the app’s business logic by applying the MVVM pattern and data binding. Then we will focus on building out a layer of plugin-like services that handle platform-specific utilities such as navigation, geo-location, and the camera, as well as how to use these services with inversion of control and dependency injection. Next we’ll connect the app to a live web-based API and set up offline synchronization. Then, we’ll dive into testing the app—both the app logic through unit tests and the user interface using Xamarin’s UITest framework. Finally, we’ll integrate Xamarin Insights for monitoring usage and bugs to gain a proactive edge on app quality.
Table of Contents (17 chapters)

Navigation and MVVM


One of the key purposes of the MVVM pattern is to isolate an app's presentation layer from its other layers; in doing so, an app's business logic is also isolated. One of the thoughts behind this isolation is to have a user interface that is only concerned with displaying data and that is completely independent of how that data is stored, acquired, manipulated, or shared with the rest of the app. As explained in Chapter 2, MVVM and DataBinding, this is typically accomplished through databinding. In MVVM, the actions that a user takes on a page are bound to commands on that page's backing ViewModel. It is very common for actions to result in a transition to another page—either by directly linking to it or by automatically navigating to a previous page after performing a task, such as saving data. Because of this, it makes sense to rethink how we do navigation in an app that leverages the MVVM pattern so that it can be controlled by ViewModels and not by the pages.

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