GoToAsync Failed With Java.Lang.IllegalStateException

Fan Yang 0

In my ViewModel, I had a relaycommand to navigation another page:

[RelayCommand]
public async Task ReviewIt () {
   ...
   await Shell.Current.GoToAsync(nameof(ReviewItView), new Dictionary<string, object>{
       ["key1"] = value1,
       ["key2"] = value2
   });
}

but it ends with exception:
Java.Lang.IllegalStateException: 'The specified child already has a parent. You must call removeView() on the child's parent first.'

how to fix this?

Leon Lu (Shanghai Wicresoft Co,.Ltd.) 71,591 Reputation points Microsoft Vendor

2024-06-24T06:54:33.2966667+00:00

Could you minimize code to just what is needed to reproduce the problem?

Please share ReviewItView's background code. Is the type of ContentPage?

Where you get the value of Dictionary? In the layout background code or the ViewModel.

Please share your .NET version.

Fan Yang 0

When targeting either Windows or iOS, the navigation works as expected; only had CLR exception when targeting Android. The stack is: App >> AppShell >> Shell >> FlyoutItem >> Tab >> ReviewIt. The flyout Item is defined as:

<FlyoutItem Title="Home" Icon="{FontImageSource Glyph={x:Static helpers:FontAwesomeIcons.Building}, FontFamily='FontAwesome', Size=20}">
    <Tab>
        <ShellContent x:Name="HomePageContent" ContentTemplate="{DataTemplate views:HomeView}" />
    </Tab>
</FlyoutItem>

In the HomePage,

[RelayCommand]
public async Task NavigateToPageA () {
  await Shell.Current.GoToAsync("//{nameof(HomePage)/{nameof(PageA)?param=value");
}

and on PageA, I have a similar relaycommand to navigate to ReviewIt page:

[RelayCommand]
public async Task ReviewIt () {
   ...
   await Shell.Current.GoToAsync(nameof(ReviewItView), new Dictionary<string, object>{
       ["key1"] = value1,
       ["key2"] = value2
   });
}

Leon Lu (Shanghai Wicresoft Co,.Ltd.) 71,591 Reputation points Microsoft Vendor

2024-06-26T07:04:21.6+00:00
How did you register these pages in the AppShell.xaml.cs?

If you register like following code.

Routing.RegisterRoute("HomeView", typeof(HomeView)); Routing.RegisterRoute("PageA", typeof(PageA)); Routing.RegisterRoute("ReviewItView", typeof(ReviewItView));

When you execute the navigation, you can try to use following code.

[RelayCommand] public async Task NavigateToPageA() { await Shell.Current.GoToAsync($"PageA?param=value"); }

Fan Yang 0

In AppShell.xaml.cs I had:

HomePageContent.Route = "HomeView";
Routing.RegisterRoute("PageA", typeof(PageA));
Routing.RegisterRoute("ReviewItView", typeof(ReviewItView));

Leon Lu (Shanghai Wicresoft Co,.Ltd.) 71,591 Reputation points Microsoft Vendor

2024-06-27T07:06:02.2166667+00:00
Please use following code when you navigate from HomePage to the PageA. Is that working?

[RelayCommand] public async Task NavigateToPageA() { await Shell.Current.GoToAsync($"PageA?param=value"); }

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GoToAsync Failed With Java.Lang.IllegalStateException