如何为现有UWP XAML应用添加Xamarin Forms以支持安卓与iOS？

Hey Jim, great question! Here's a step-by-step breakdown of the best approach to add Xamarin.Forms support to your existing UWP XAML app, plus some resources to guide you:

1. Refactor Shared Logic and UI First #

• Start by auditing your UWP app to spot shared business logic (like data services, view models if you use MVVM, and utility classes) that can be moved to a .NET Standard class library. Xamarin.Forms works natively with .NET Standard, so this will be your core shared layer across all platforms.
• For XAML UI, begin porting UWP-specific controls to their Xamarin.Forms equivalents. For example, swap TextBlock with Label, UWP Grid with Xamarin.Forms Grid, and Button (UWP) with Xamarin.Forms Button. Be mindful of subtle layout or behavior differences between platforms—you might need to adjust properties like Padding or HorizontalOptions for consistency.

2. Set Up a Xamarin.Forms Solution Structure #

• Create a new Xamarin.Forms solution in Visual Studio (use the "Mobile App (Xamarin.Forms)" template) which includes the shared project, Android, and iOS projects.
• Add your existing UWP project to this new solution. Now you’ll have a unified solution with all three target platforms plus the shared Xamarin.Forms layer.

3. Wire Up UWP to Xamarin.Forms #

• Install the Xamarin.Forms NuGet package in your existing UWP project.
• Update your UWP app’s App.xaml.cs to initialize Xamarin.Forms on launch. Replace the default initialization code with something like this:

  protected override void OnLaunched(LaunchActivatedEventArgs e)
  {
      Xamarin.Forms.Forms.Init(e);
      
      Frame rootFrame = Window.Current.Content as Frame;
      if (rootFrame == null)
      {
          rootFrame = new Frame();
          rootFrame.NavigationFailed += OnNavigationFailed;
          Window.Current.Content = rootFrame;
      }
  
      if (e.PrelaunchActivated == false)
      {
          if (rootFrame.Content == null)
          {
              // Navigate to your shared Xamarin.Forms main page instead of UWP-specific pages
              rootFrame.Navigate(typeof(MainPage), e.Arguments);
          }
          Window.Current.Activate();
      }
  }
  

• Create a MainPage in your shared Xamarin.Forms project, then migrate your UWP pages to this shared project one by one. For any UWP-specific functionality that can’t be replaced (like accessing UWP APIs), use Xamarin.Forms Dependency Service to call platform-specific code from the shared layer.

4. Test Incrementally #

• Don’t attempt to port your entire app in one go! Start with a small, self-contained feature (like a settings page or a simple data display) to work out integration kinks.
• Test each platform as you progress: use Android/iOS simulators and your existing UWP environment to ensure behavior is consistent across all targets.

• Microsoft Official Documentation: Look for the "Integrate Xamarin.Forms with Existing Apps" guide. It walks through this exact scenario, including UWP-specific setup, dependency service implementation, and best practices for project structure.
• UWP to Xamarin.Forms Migration Video Series: There are hands-on video tutorials that focus on migrating UWP apps to Xamarin.Forms. Look for content that covers refactoring to .NET Standard, porting XAML layouts, and handling platform-specific edge cases.
• MVVM Adaptation Guides: If your UWP app uses an MVVM framework (like Prism or MvvmLight), seek out resources that show how to adapt those frameworks to work with Xamarin.Forms—this will save you from reworking your view model logic from scratch.

内容的提问来源于stack exchange，提问作者Jim