Getting "Java.Lang.IllegalStateException" error with bottom navigation bar on Android device

Question

Getting "Java.Lang.IllegalStateException" error with bottom navigation bar on Android device

Michael Alfred 25

I have created a bottom navigation bar for my Maui app, which was working perfectly fine. However, after I created another page, I started getting the following error on my Android device: "Java.Lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first."

I have tried running the app on my Windows machine and it works perfectly fine without any errors, so I believe this issue is specific to Android devices. I have already tried looking for solutions online, but I couldn't find anything that worked for me.

Here's the code for my bottom navigation bar:

AppShell.xaml

**

  <ShellContent  ContentTemplate="{DataTemplate View:MainPage}" />

       <ShellContent ContentTemplate="{DataTemplate View:Registration}"/>

    

    

    <!--When the user is logged in the bottom nav appears-->

    <TabBar Route="DeriTabBar">

        <Tab Title="Home" Icon="deri_food_logo.png">

            <ShellContent ContentTemplate="{DataTemplate View:Dashboard}" Route="Dashboard"/>

        </Tab>

        <Tab Title="Login" Icon="deri_food_logo.png">

            <ShellContent ContentTemplate="{DataTemplate View:Login}"  Route="Login"/>

        </Tab>

        <Tab Title="Restaurant" Icon="deri_food_logo.png">

            <ShellContent ContentTemplate="{DataTemplate View:Restaurant}"  Route="Restaurant"/>

        </Tab>

    </TabBar>**



Registration Viewmodel

**await Shell.Current.GoToAsync($"//DeriTabBar/{nameof(Dashboard)}?email={Email}"); ** 

and here is code that navigates to the dashboard with the email parameter

Anonymous

2023-03-15T05:34:57.75+00:00
Please share steps that could reproduce this issue.

I copy your code in my demo and I register all of page in the AppShell background code, it is working. I can navigate with await Shell.Current.GoToAsync($"//DeriTabBar/{nameof(Dashboard)}?email={Email}");.

public AppShell() { InitializeComponent(); Routing.RegisterRoute("Dashboard", typeof(Dashboard)); }

Michael Alfred 25

So sorry @Anonymous for not providing all the steps

This is the appshell.xaml.cs file where I register all the routes for the application


public AppShell()
	{
		InitializeComponent();

        Routing.RegisterRoute(nameof(Login), typeof(Login));
        Routing.RegisterRoute(nameof(Registration), typeof(Registration));
        Routing.RegisterRoute(nameof(Dashboard), typeof(Dashboard));
        Routing.RegisterRoute(nameof(Restaurant), typeof(Restaurant));
    }

And Appshell.xaml file is where I define the routes for navigating within the application.


<Shell
    x:Class="Deri.AppShell"
    xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:View="clr-namespace:Deri"
    Shell.FlyoutBehavior="Disabled">

    
    <ShellContent  ContentTemplate="{DataTemplate View:MainPage}" />
    <ShellContent ContentTemplate="{DataTemplate View:Registration}"/>



    <TabBar Route="DeriTabBar">
        <Tab Title="Home" Icon=" deri_food_logo.png">
            <ShellContent ContentTemplate="{DataTemplate View:Dashboard}" Route="Dashboard"/>
        </Tab>

	<Tab Title="Login" Icon="deri_food_logo.png">
            <ShellContent ContentTemplate="{DataTemplate View: Login}" Route=" Login"/>
        </Tab>

        <Tab Title="Restaurant" Icon=" deri_food_logo.png">
            <ShellContent ContentTemplate="{DataTemplate View:Restaurant}"  Route="Restaurant"/>
        </Tab>
    </TabBar>


</Shell>

The registration viewmodel contains a private async void method that creates a user account, and if all the details entered are correct, the registration page navigates to the dashboard page. I have tested this functionality on my end, and it works properly.


private async void Register(){
if (deriuser) 
  {
    await Shell.Current.DisplayAlert("Success (Deri 19)", $"Registration        Successful", "Ok");

    await Shell.Current.GoToAsync($"//DeriTabBar/{nameof(Dashboard)}?   email={Email}");
   }
}

After navigating to the dashboard(Home), i tried to navigate to other pages like the restaurant and login, the issue arose when I tried to navigate from either the login page or the restaurant page back to the dashboard page(Home) using the routes defined in appshell.xaml. I am encountering the "Java.Lang.IllegalStateException" error at this point, as the application enters break mode and I am unable to navigate back to the dashboard page. See the image below

Note: The code works without any issues on the Windows machine. However, when I run it on my local Android device, I get the error"

Screenshot_20230314_033650_com.companyname.deri

Anonymous

2023-03-16T07:24:01.05+00:00
After navigating to the dashboard(Home), i tried to navigate to other pages like the restaurant and login, the issue arose when I tried to navigate from either the login page or the restaurant page back to the dashboard page(Home) using the routes defined in appshell.xaml

I use following code in the Dashboard page navigate to the login, it is working. Please share a mini demo(upload this demo to github, share link here) that could reproduce this issue, it is better.

await Shell.Current.GoToAsync($"//DeriTabBar/{nameof(Login)}");
Michael Alfred 25 Reputation points

2023-03-16T12:50:24.7+00:00
@Anonymous Yes navigating from the dashboard to the login using this would work

await Shell.Current.GoToAsync($"//DeriTabBar/{nameof(Login)}");

But is there a way register ($"//DeriTabBar/nameof(Login)}"}; as a route in the Appshell?

The bottom navigation bar, gets the route to other pages from the Appshell, so if i could find a way to register that route in the Appshell i think it might work and stop my application from going into break mode.

If this doesn't work, i would upload a demo to github, then share the link here
Anonymous

2023-03-21T08:45:52.1966667+00:00

Michael Alfred

is there a way register ($"//DeriTabBar/nameof(Login)}"}; as a route in the Appshell?

Yes, you can register Routing.RegisterRoute("DeriTabBar/Login", typeof(Login)); in AppShell.cs, then use await Shell.Current.GoToAsync($"//DeriTabBar/{nameof(Login)}"); directly.
Anonymous

2023-03-24T06:03:36.18+00:00

May I know if you have got any chance to check my comment? I am glad to help if you have any other questions.

1 answer

Your answer

Anonymous

2023-03-15T05:34:57.75+00:00

Please share steps that could reproduce this issue.

I copy your code in my demo and I register all of page in the AppShell background code, it is working. I can navigate with await Shell.Current.GoToAsync($"//DeriTabBar/{nameof(Dashboard)}?email={Email}");.

public AppShell() { InitializeComponent(); Routing.RegisterRoute("Dashboard", typeof(Dashboard)); }
Anonymous

2023-03-16T07:24:01.05+00:00

After navigating to the dashboard(Home), i tried to navigate to other pages like the restaurant and login, the issue arose when I tried to navigate from either the login page or the restaurant page back to the dashboard page(Home) using the routes defined in appshell.xaml

I use following code in the Dashboard page navigate to the login, it is working. Please share a mini demo(upload this demo to github, share link here) that could reproduce this issue, it is better.

await Shell.Current.GoToAsync($"//DeriTabBar/{nameof(Login)}");
Michael Alfred 25 Reputation points

2023-03-16T12:50:24.7+00:00

@Anonymous Yes navigating from the dashboard to the login using this would work

await Shell.Current.GoToAsync($"//DeriTabBar/{nameof(Login)}");

But is there a way register ($"//DeriTabBar/nameof(Login)}"}; as a route in the Appshell?

The bottom navigation bar, gets the route to other pages from the Appshell, so if i could find a way to register that route in the Appshell i think it might work and stop my application from going into break mode.

If this doesn't work, i would upload a demo to github, then share the link here
Anonymous

2023-03-21T08:45:52.1966667+00:00

Michael Alfred

is there a way register ($"//DeriTabBar/nameof(Login)}"}; as a route in the Appshell?

Yes, you can register Routing.RegisterRoute("DeriTabBar/Login", typeof(Login)); in AppShell.cs, then use await Shell.Current.GoToAsync($"//DeriTabBar/{nameof(Login)}"); directly.
Anonymous

2023-03-24T06:03:36.18+00:00

May I know if you have got any chance to check my comment? I am glad to help if you have any other questions.

Answer 1

Ahmed Thabet Elshamandy 40

@Michael Alfred

Hi Michael,

Me too found this exception in my application . but I use await Navigation.PushAsync()
when using pushAsync and popAsync functions . to go to another page or to go back .not used shell .

I tried to search but not found any solution.

Please if you found any thing help us to fix it , share it

Thank You,

Michael Alfred 25 Reputation points

2023-10-29T09:45:06.64+00:00
@Ahmed Thabet Elshamandy

Hi Ahmed,

I see that you've encountered an exception when using Navigation.PushAsync() for page navigation in your application. I'd be happy to help you troubleshoot this issue. Can you provide more details about the exception you're facing? Knowing the specific exception message and any associated stack traces would be helpful in diagnosing the problem.

Feel free to share any relevant code snippets or details about the context in which you're using PushAsync. The more information you provide, the better I can assist you in resolving this issue.

Try surrounding your PushAsync call with a try-catch block to catch any exceptions and log them for debugging purposes. for example

try { await Navigation.PushAsync(new YourPage()); } catch (Exception ex) { Debug.WriteLine("Navigation error: " + ex.Message); }

And also make sure await Navigation.PushAsync() is being called from the main UI thread. If you are trying to navigate from a background thread, it can lead to issues.

Also, feel free to check out this answer I found on Stack Overflow to see if it addresses your question.

https://stackoverflow.com/a/47342356
Michael Alfred 25 Reputation points

2023-10-29T09:51:01.26+00:00
Hi Ahmed,

I see that you've encountered an exception when using Navigation.PushAsync() for page navigation in your application. I'd be happy to help you troubleshoot this issue. Can you provide more details about the exception you're facing? Knowing the specific exception message and any associated stack traces would be helpful in diagnosing the problem.

Feel free to share any relevant code snippets or details about the context in which you're using PushAsync. The more information you provide, the better I can assist you in resolving this issue.

Try surrounding your PushAsync call with a try-catch block to catch any exceptions and log them for debugging purposes.

try { await Navigation.PushAsync(new YourPage()); } catch (Exception ex) { Debug.WriteLine("Navigation error: " + ex.Message); }

Also, feel free to check out this answer I found on Stack Overflow to see if it addresses your question.

https://stackoverflow.com/a/47342356
Ahmed Thabet Elshamandy 40 Reputation points

2023-10-29T11:07:47.6733333+00:00
@Michael Alfred

Thank you for your help,

On click on Button which navigation to another page and this function which handle the event

private async void New_PlanOption(object sender, TappedEventArgs eventArgs) { try{ var go = new SmartCafeteriaItems(iteml, 0, 0, _empid, 0); await Navigation.PushAsync(go); } catch (Exception ex) { Debug.WriteLine("Navigation error: " + ex.Message); } }

After that it must go to SmartCafeteriaItems page but , It give me an exception say that Java.Lang.IllegalStateException: 'The specified child already has a parent. You must call removeView() on the child's parent first.'

Not in catch statment but in JNINativeWrapper.cs file.

thanks a lot,
Michael Alfred 25 Reputation points

2023-10-29T12:14:33.64+00:00
@Ahmed Thabet Elshamandy

Awesome Ahmed,

Thank you for sharing more details. Creating a new instance of SmartCafeteriaItems each time you navigate to it is indeed the right approach to prevent the "Java.Lang.IllegalStateException" error, and you've already implemented it correctly.

One thing to consider, based on the error message you're encountering, is whether you're using the Inflate method within your SmartCafeteriaItems page to create a view from a layout resource. It's important to specify the parent view group or set the attachToRoot parameter to false appropriately to avoid conflicts.

You might want to check if you have any code like this:

View view = LayoutInflater.From(Context).Inflate(Resource.Layout.SomeLayout, null);

In this case, it's important to pass the parent view group as the second parameter of the Inflate method

View view = LayoutInflater.From(Context).Inflate(Resource.Layout.SomeLayout, ContentPage.Content as ViewGroup);

OR

pass false as the third parameter.

View view = LayoutInflater.From(Context).Inflate(Resource.Layout.SomeLayout, null, false);

If you still have issues utilize the page lifecycle event to remove an existing SmartCafeteriaItems page if it is on the navigation stack, it should be removed before navigating to a new instance.

protected override void OnDisappearing() { base.OnDisappearing(); var existingPage = Navigation.NavigationStack.FirstOrDefault(p => p is SmartCafeteriaItems); if (existingPage is SmartCafeteriaItems){ Navigation.RemovePage(existingPage); } }
Ahmed Thabet Elshamandy 40 Reputation points

2023-10-29T13:50:46.9166667+00:00
Dear @Michael Alfred ,

Thanks a lot for your effort.

but I did not use Inflate method in my solution before I just need to go to SmartCafeteriaItems

page which has xaml file . I tried to search to another way to navigate but I have the same exception.

And also now tried this

protected override void OnDisappearing() { base.OnDisappearing(); var existingPage = Navigation.NavigationStack.FirstOrDefault(p => p is SmartCafeteriaItems); if (existingPage is SmartCafeteriaItems){ Navigation.RemovePage(existingPage); } }

but still have the same exception.

Thank you.
Michael Alfred 25 Reputation points

2023-10-29T14:13:38.5933333+00:00

Hi Ahmed,

Thank you for the update. If you're certain that the view inflation and the OnDisappearing method are not the root causes, I would recommend carefully reviewing the entire navigation flow within your application.

Ensure that you don't have non-linear navigation patterns, such as nested navigation or scenarios where a page is not properly removed from the navigation stack before navigating back to it. Non-standard navigation sequences can introduce complexities and unexpected behavior.

Additionally, it might be beneficial to reach out to experts in the Xamarin.Forms and .NET MAUI community for their insights @James Montemagno @Gerald Versluis @Anonymous They have extensive experience and could provide valuable guidance.

Wishing you the best of luck in resolving this issue, Ahmed. I hope you find a solution with the help of the community and experts.
Ahmed Thabet Elshamandy 40 Reputation points

2023-10-29T14:29:47.05+00:00

Dear @Michael Alfred ,

Thanks a lot for your efforts Wishing you the best of luck.

I hope to finds you well .

Thanks You,

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Getting "Java.Lang.IllegalStateException" error with bottom navigation bar on Android device

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