带有 Prism 的表单：应用程序 windows 应具有根 VC

Question

我刚刚在我的新应用程序中实现了 Prism 库，并且我正在使用 NavigationService。它在 Android 上运行良好，但是当我尝试在网络 Mac 上调试我的 Xamarin Forms iOS 应用程序时，我的 Main 方法抛出此异常：

  Unhandled Exception:

Foundation.MonoTouchException: Objective-C exception thrown.  Name: NSInternalInconsistencyException Reason: Application windows are expected to have a root view controller at the end of application launch
Native stack trace:
    0   CoreFoundation                      0x00000001021f2b0b __exceptionPreprocess + 171
    1   libobjc.A.dylib                     0x000000010cdcf141 objc_exception_throw + 48
    2   CoreFoundation                      0x00000001021f6cf2 +[NSException raise:format:arguments:] + 98
    3   Foundation                          0x0000000102da93b6 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 193
    4   UIKit                               0x0000000105ba0be6 -[UIApplication _runWithMainScene:transitionContext:completion:] + 3343
    5   UIKit                               0x0000000105b9d793 -[UIApplication workspaceDidEndTransaction:] + 182
    6   FrontBoardServices                  0x000000010fae35f6 __FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK__ + 24
    7   FrontBoardServices                  0x000000010fae346d -[FBSSerialQueue _performNext] + 186
    8   FrontBoardServices                  0x000000010fae37f6 -[FBSSerialQueue _performNextFromRunLoopSource] + 45
    9   CoreFoundation                      0x0000000102198c01 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    10  CoreFoundation                      0x000000010217e0cf __CFRunLoopDoSources0 + 527
    11  CoreFoundation                      0x000000010217d5ff __CFRunLoopRun + 911
    12  CoreFoundation                      0x000000010217d016 CFRunLoopRunSpecific + 406
    13  UIKit                               0x0000000105b9c02f -[UIApplication _run] + 468
    14  UIKit                               0x0000000105ba20d4 UIApplicationMain + 159
    15  ???                                 0x0000000124f647fc 0x0 +

我的主要方法是这样的：

static void Main(string[] args)
        {
            // if you want to use a different Application Delegate class from "AppDelegate"
            // you can specify it here.
            UIApplication.Main(args, null, "AppDelegate");
        }

AppDelegate:

[Register("AppDelegate")]
    public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
    {

        // This method is invoked when the application has loaded and is ready to run. In this 
        // method you should instantiate the window, load the UI into it and then make the window
        // visible.
        //
        // You have 17 seconds to return from this method, or iOS will terminate your application.
        public override bool FinishedLaunching(UIApplication app, NSDictionary options)
        {
            global::Xamarin.Forms.Forms.Init();
            this.LoadApplication(new Core.CitizenApp());

            return base.FinishedLaunching(app, options);
        }
    }

表单应用程序：

protected override void OnInitialized()
    {
        this.InitializeComponent();
        NavigationService.NavigateAsync("LaunchPage");
        return;
    }

如有任何帮助，我们将不胜感激。我有 Xamarin、Xamarin Forms、Prism 和 Visual Studio 的最新更新，我不确定可能是什么问题。

Answer 1

您的 LaunchPage 抛出异常。更新 OnInitialized 使其更像这样：

protected override async void OnInitialized()
{
    try
    {
        TaskScheduler.UnobservedTaskException += (sender, e) => {
            Logger.Log(e.Exception.ToString(), Category.Exception, Priority.High);
        };
        await NavigationService.NavigateAsync("LaunchPage");
    }
    catch(Exception e)
    {
        Logger.Log(e.Exception.ToString(), Category.Exception, Priority.High);
    }
}

这至少可以帮助您确定异常是什么。没有看到你的项目很难说，但我可能猜想你正在使用 IPlatformInitializer 并在 Android 而不是 iOS 上注册了一些东西，或者你依赖于 Xamarin Forms Dependency Service 并且存在依赖关系在 Android 但不是 iOS。

带有 Prism 的表单：应用程序 windows 应具有根 VC

Forms with Prism: Application windows are expected to have a root VC

c#

prism

xamarin.ios

xamarin

xamarin.forms