大家好，我不断收到以下信息:
带有的System.InvalidOperationException“iOS上不全局支持PushAsync，请使用NavigationPage。”
即使我使用了NavigationPage并根据我的判断正确使用了它。我的F＃技能并不出色，因此我肯定认为我在这里做错了，但是，出人意料地发现在F＃中很难找到执行Navigation.PushAsync的示例。我确实找到了这段代码，并一直在寻找一个正确的例子。
https://github.com/fsprojects/Tamarin/blob/master/samples/Todo/TodoListMvc.fs
在示例中，我看到此代码包装在async{}中
do! this.Navigation.PushAsync(page = downcast view.Root) |> Async.AwaitIAsyncResult |> Async.Ignore
所以我认为我离这里不太远。这么说，我在做什么错？
AssemblyVersions
码
namespace Eclipsefest
open System
open Xamarin.Forms
open Xamarin.Forms.Xaml
type MenuItem =
{ Title : string
TargetType : System.Type }
type MenuPage() =
inherit ContentPage()
let _ = base.LoadFromXaml(typeof<MenuPage>)
member this.Handle_Tapped(sender : Object, arg : EventArgs) =
let navItem = sender :?> TextCell
async {
match navItem.Text with
| "Information" ->
do! this.Navigation.PushAsync(page = new NavigationPage(new InfoPage()))
|> Async.AwaitIAsyncResult
|> Async.Ignore
| "Events" ->
do! this.Navigation.PushAsync(new NavigationPage(new EventsPage()))
|> Async.AwaitIAsyncResult
|> Async.Ignore
| "BusRoute" ->
do! this.Navigation.PushAsync(new NavigationPage(new BusRoutePage()))
|> Async.AwaitIAsyncResult
|> Async.Ignore
| "Glasses" ->
do! this.Navigation.PushAsync(new NavigationPage(new GlassesPage()))
|> Async.AwaitIAsyncResult
|> Async.Ignore
| "Merch" ->
do! this.Navigation.PushAsync(new NavigationPage(new MerchPage()))
|> Async.AwaitIAsyncResult
|> Async.Ignore
| "Day" ->
do! this.Navigation.PushAsync(new NavigationPage(new DayPage()))
|> Async.AwaitIAsyncResult
|> Async.Ignore
| "About" ->
do! this.Navigation.PushAsync(new NavigationPage(new AboutPage()))
|> Async.AwaitIAsyncResult
|> Async.Ignore
| _ ->
do! this.Navigation.PushAsync(new NavigationPage(new EclipsefestPage()))
|> Async.AwaitIAsyncResult
|> Async.Ignore
}
|> Async.RunSynchronously
代码更新
open System
open Xamarin.Forms
open Xamarin.Forms.Xaml
type MenuItem =
{ Title : string
TargetType : System.Type }
type MenuPage() =
inherit ContentPage()
let _ = base.LoadFromXaml(typeof<MenuPage>)
member this.Handle_Tapped(sender : Object, arg : EventArgs) =
this.Navigation.PushAsync(new NavigationPage(new EclipsefestPage())) |> ignore
我也尝试了这一点，并收到了相同的错误。我怀疑我的问题与异步部分有关，但似乎在没有异步的情况下也会抛出相同的异常。
代码更新2
open System
open Xamarin.Forms
open Xamarin.Forms.Xaml
type MenuItem =
{ Title : string
TargetType : System.Type }
type MenuPage() =
inherit ContentPage()
let _ = base.LoadFromXaml(typeof<MenuPage>)
member this.Handle_Tapped(sender : Object, arg : EventArgs) =
let page = new EclipsefestPage()
let navpage = new NavigationPage(page)
let result = this.Navigation.PushAsync(navpage)
result.RunSynchronously()
我开始感觉到这是一个错误。我已经验证了该页面和导航页面在调用
Navigation.PushAsync之前是在各个步骤中实例化的，并且仍然会遇到相同的异常。错误
“iOS上不全局支持PushAsync，请使用NavigationPage。”
堆栈跟踪
System.InvalidOperationException: PushAsync is not supported globally on iOS, please use a NavigationPage.
at Xamarin.Forms.Platform.iOS.Platform.Xamarin.Forms.INavigation.PushAsync (Xamarin.Forms.Page root, System.Boolean animated) [0x00000] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Platform.iOS\Platform.cs:154
at Xamarin.Forms.NavigationProxy.OnPushAsync (Xamarin.Forms.Page page, System.Boolean animated) [0x00022] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\NavigationProxy.cs:190
at Xamarin.Forms.NavigationProxy.PushAsync (Xamarin.Forms.Page root, System.Boolean animated) [0x00013] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\NavigationProxy.cs:109
at Xamarin.Forms.NavigationProxy.OnPushAsync (Xamarin.Forms.Page page, System.Boolean animated) [0x00022] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\NavigationProxy.cs:190
at Xamarin.Forms.NavigationProxy.PushAsync (Xamarin.Forms.Page root, System.Boolean animated) [0x00013] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\NavigationProxy.cs:109
at Xamarin.Forms.NavigationProxy.OnPushAsync (Xamarin.Forms.Page page, System.Boolean animated) [0x00022] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\NavigationProxy.cs:190
at Xamarin.Forms.NavigationProxy.PushAsync (Xamarin.Forms.Page root, System.Boolean animated) [0x00013] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\NavigationProxy.cs:109
at Xamarin.Forms.NavigationProxy.PushAsync (Xamarin.Forms.Page root) [0x00000] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\NavigationProxy.cs:102
at <StartupCode$Eclipsefest>[email protected] (Microsoft.FSharp.Core.Unit unitVar) [0x00090] in /Users/terrancesmith/Projects/Eclipsefest/Eclipsefest/MenuPage.xaml.fs:19
at Microsoft.FSharp.Control.AsyncBuilderImpl+callA@851[b,a].Invoke (Microsoft.FSharp.Control.AsyncParams`1[T] args) [0x00047] in <5584acdb904cf4daa7450383dbac8455>:0
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.36/src/mono/mcs/class/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:151
at Microsoft.FSharp.Control.AsyncBuilderImpl.commit[a] (Microsoft.FSharp.Control.AsyncBuilderImpl+Result`1[T] res) [0x00030] in <5584acdb904cf4daa7450383dbac8455>:0
at Microsoft.FSharp.Control.CancellationTokenOps.RunSynchronously[a] (System.Threading.CancellationToken token, Microsoft.FSharp.Control.FSharpAsync`1[T] computation, Microsoft.FSharp.Core.FSharpOption`1[T] timeout) [0x000a3] in <5584acdb904cf4daa7450383dbac8455>:0
at Microsoft.FSharp.Control.FSharpAsync.RunSynchronously[T] (Microsoft.FSharp.Control.FSharpAsync`1[T] computation, Microsoft.FSharp.Core.FSharpOption`1[T] timeout, Microsoft.FSharp.Core.FSharpOption`1[T] cancellationToken) [0x00071] in <5584acdb904cf4daa7450383dbac8455>:0
at Eclipsefest.MenuPage.Handle_Tapped (System.Object sender, System.EventArgs arg) [0x00008] in /Users/terrancesmith/Projects/Eclipsefest/Eclipsefest/MenuPage.xaml.fs:16
at Xamarin.Forms.Cell.OnTapped () [0x00008] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\Cells\Cell.cs:106
at Xamarin.Forms.TextCell.OnTapped () [0x00000] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\Cells\TextCell.cs:82
at Xamarin.Forms.TableView+TableSectionModel.OnRowSelected (System.Object item) [0x00007] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\TableView.cs:214
at Xamarin.Forms.TableModel.RowSelected (System.Object item) [0x0001a] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\TableModel.cs:65
at Xamarin.Forms.TableModel.RowSelected (System.Int32 section, System.Int32 row) [0x00000] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\TableModel.cs:57
at Xamarin.Forms.Platform.iOS.TableViewModelRenderer.RowSelected (UIKit.UITableView tableView, Foundation.NSIndexPath indexPath) [0x00000] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Platform.iOS\Renderers\TableViewModelRenderer.cs:85
at at (wrapper managed-to-native) UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)
at UIKit.UIApplication.Main (System.String[] args, System.IntPtr principal, System.IntPtr delegate) [0x00005] in /Users/builder/data/lanes/4691/d2270eec/source/xamarin-macios/src/UIKit/UIApplication.cs:79
at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x00038] in /Users/builder/data/lanes/4691/d2270eec/source/xamarin-macios/src/UIKit/UIApplication.cs:63
at Eclipsefest.iOS.Main.main (System.String[] args) [0x00001] in <59853c0a6da8a60ca74503830a3c8559>:0
最佳答案
回答来自Xamarin的人们。
在显示的代码中，您正在包装要推送的新页面
在NavigationPage中。但是这是您从中推送的页面
需要在导航页面中。
最简单的方法是将初始页面包装在
然后将NavigationPage设置为MainPage。然后，您只需推动新
直接浏览页面而无需将其包装在另一个NavigationPage中，因为
这样做会导致其他问题。看看这个:
https://gist.github.com/jimmgarrido/d0b702c1282faa5bb91d0ed14e2d7e1b
namespace FForms
open System
open Xamarin.Forms
type TestPage() as this =
inherit ContentPage()
let nextBtn = Button(Text = "Next Page")
let layout = StackLayout()
let handler = EventHandler(fun sender args ->
let newPage = ContentPage(BackgroundColor = Color.Red)
do this.Navigation.PushAsync(newPage))
do nextBtn.Clicked.AddHandler handler
do layout.Children.Add nextBtn
do base.Content <- layout
type App() =
inherit Application(MainPage = NavigationPage(TestPage()))
希望这可以帮助!
做到了〜