Java.Lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.ColorStateList com.google.android.material.navigation.NavigationBarMenuView.getItemTextColor()' on a null object reference

[LeoJHarris]

Android framework version

net9.0-android

Affected platform version

Version 17.12.4

Description

Running our app in Release Configuration with r8 enabled is throwing the following exception as per the logcat, when r8 is disabled we don't get the crash.

Steps to Reproduce

Running the app in Release config with r8 enabled and run the app... crash,

Did you find any workaround?

Disabling r8

Relevant log output

Time	Device Name	Type	PID	Tag	Message
01-17 15:49:34.695	Samsung SM-G991U	Info	12591	MonoDroid	Java.Lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.ColorStateList com.google.android.material.navigation.NavigationBarMenuView.getItemTextColor()' on a null object reference
   at Java.Interop.JniEnvironment.InstanceMethods.CallObjectMethod(JniObjectReference instance, JniMethodInfo method, JniArgumentValue* args)
   at Java.Interop.JniPeerMembers.JniInstanceMethods.InvokeVirtualObjectMethod(String encodedMember, IJavaPeerable self, JniArgumentValue* parameters)
   at Google.Android.Material.Navigation.NavigationBarView.get_ItemTextColor()
   at Microsoft.Maui.Controls.Handlers.TabbedPageManager.GetItemTextColorStates()
   at Microsoft.Maui.Controls.Handlers.TabbedPageManager.UpdateBarTextColor()
   at Microsoft.Maui.Controls.Handlers.TabbedPageManager.UpdateTabItemStyle()
   at Microsoft.Maui.Controls.TabbedPage.MapBarTextColor(ITabbedViewHandler handler, TabbedPage view)
   at Microsoft.Maui.PropertyMapperExtensions.<>c__DisplayClass2_0`2[[Microsoft.Maui.Controls.TabbedPage, Microsoft.Maui.Controls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Handlers.ITabbedViewHandler, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].<ReplaceMapping>b__0(ITabbedViewHandler h, TabbedPage v, Action`2 p)
   at Microsoft.Maui.PropertyMapperExtensions.<>c__DisplayClass1_0`2[[Microsoft.Maui.Controls.TabbedPage, Microsoft.Maui.Controls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Handlers.ITabbedViewHandler, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].<ModifyMapping>g__newMethod|0(IElementHandler handler, IElement view)
   at Microsoft.Maui.PropertyMapper`2.<>c__DisplayClass5_0[[Microsoft.Maui.ITabbedView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Handlers.ITabbedViewHandler, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].<Add>b__0(IElementHandler h, IElement v)
   at Microsoft.Maui.PropertyMapper.UpdatePropertyCore(String key, IElementHandler viewHandler, IElement virtualView)
   at Microsoft.Maui.PropertyMapper.UpdateProperties(IElementHandler viewHandler, IElement virtualView)
   at Microsoft.Maui.Handlers.ElementHandler.SetVirtualView(IElement view)
   at Microsoft.Maui.Handlers.ViewHandler`2[[Microsoft.Maui.ITabbedView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Android.Views.View, Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065]].SetVirtualView(IView view)
   at Microsoft.Maui.Handlers.ViewHandler`2[[Microsoft.Maui.ITabbedView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Android.Views.View, Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065]].SetVirtualView(IElement view)
   at Microsoft.Maui.Controls.Element.SetHandler(IElementHandler newHandler)
   at Microsoft.Maui.Controls.Element.set_Handler(IElementHandler value)
   at Microsoft.Maui.Controls.VisualElement.Microsoft.Maui.IElement.set_Handler(IElementHandler value)
   at Microsoft.Maui.Platform.ElementExtensions.ToHandler(IElement view, IMauiContext context)
   at Microsoft.Maui.Platform.ElementExtensions.ToPlatform(IElement view, IMauiContext context)
   at Microsoft.Maui.Platform.ScopedFragment.OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
   at AndroidX.Fragment.App.Fragment.n_OnCreateView_Landroid_view_LayoutInflater_Landroid_view_ViewGroup_Landroid_os_Bundle_(IntPtr jnienv, IntPtr native__this, IntPtr native_inflater, IntPtr native_container, IntPtr native_savedInstanceState)
   at Android.Runtime.JNINativeWrapper.Wrap_JniMarshal_PPLLL_L(_JniMarshal_PPLLL_L callback, IntPtr jnienv, IntPtr klazz, IntPtr p0, IntPtr p1, IntPtr p2)
  --- End of managed Java.Lang.NullPointerException stack trace ---

[LeoJHarris]

This seems like part of a larger piece of work which is actually just getting an Android app working with r8 enabled.

[dellis1972]

r8 generally will need some work from the user to add rules to a proguard.txt file (which has a ProguardConfiguration build actions. The defaults we provide won't cover everything, as a result some of the Java types we generate as part of the build will be stripped out.

@jonathanpeppers does maui ship with proguard rules? Perhaps they should ship some defaults as well?

[jonathanpeppers]

You might try the proguard rule here:

• Prevent R8 from removing core .NET MAUI components maui#25142 (comment)

I think dotnet/maui needs to add the rule mentioned there. PlatformInterop seems like it can get stripped out.