Merged ResourceDictionary causes a null reference exception-CodePudding

In Xamarin.Forms I get a runtime Exception when I use a Merged ResourceDictionary in another ResourceDirectory when applied to a FlyoutHeader Template.

When I remove the Merged Dictionary and add the color keys directly in the FlyoutHeaderStyle.xaml Dictionary then I don't get a null reference exception.

Any help would be really appreciated.

\>>> Dictionary Colors.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ResourceDictionary xmlns="http://xamarin.com/schemas/2014/forms" 
                    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml">
    <!-- Colours Light Theme -->
    <Color x:Key="ColorForegroundText">#414141</Color>
    <Color x:Key="ColorForegroundAction">#00698F</Color>
    <Color x:Key="ColorForegroundFocus">#9163DE</Color>
    <Color x:Key="ColorForegroundMuted">#636363</Color>
    <Color x:Key="ColorForegroundBorder">#808080</Color>

    <Color x:Key="ColorBackground">#FFFFFF</Color>
    <Color x:Key="ColorBackgroundShade">#F5F5F5</Color>
    <Color x:Key="ColorBackgroundAlt">#EBEBEB</Color>
    <Color x:Key="ColorBackgroundAltShade">#E0E0E0</Color>

</ResourceDictionary>

\>>> Dictionary FlyoutHeaderStyle.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ResourceDictionary xmlns="http://xamarin.com/schemas/2014/forms" 
                    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml">

    <!--This Causes a null reference exception-->
    <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary Source="/Styles/Colors.xaml"/>
    </ResourceDictionary.MergedDictionaries>

    <!--Direct Color keys works-->
    <Color x:Key="ColorBackgroundAAA">Green</Color>

    <Style TargetType="Grid">
        <Setter Property="BackgroundColor" Value="Black"/>
        <Setter Property="HeightRequest" Value="80"/>
    </Style>

    <Style TargetType="Label">
        <Setter Property="TextColor" Value="{StaticResource Key=ColorBackgroundAAA}"/>
    </Style>


</ResourceDictionary>

>>> FlyoutHeaderControl

<?xml version="1.0" encoding="UTF-8" ?>
<ContentView
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    x:Class="knibz.Controls.FlyoutHeaderControl">
    <ContentView.Content>       
        <Grid>
            <Grid.Resources>
                  <ResourceDictionary Source="/Styles/FlyoutHeader.xaml" />
            </Grid.Resources>
            <Label Text="Knibz"/>
        </Grid>
    </ContentView.Content>

</ContentView>

Stacktrace " at Android.Runtime.JNINativeWrapper._unhandled_exception (System.Exception e) [0x0000e] in /Users/runner/work/1/s/xamarin-android/src/Mono.Android/Android.Runtime/JNINativeWrapper.g.cs:12 \n at Android.Runtime.JNINativeWrapper.Wrap_JniMarshal_PPL_V (_JniMarshal_PPL_V callback, System.IntPtr jnienv, System.IntPtr klazz, System.IntPtr p0) [0x0001d] in /Users/runner/work/1/s/xamarin-android/src/Mono.Android/Android.Runtime/JNINativeWrapper.g.cs:111 \n at (wrapper native-to-managed) Android.Runtime.JNINativeWrapper.Wrap_JniMarshal_PPL_V(intptr,intptr,intptr)"

I tried debugging the problem but still can not find the problem, I already cleaned, rebuild the solution

CodePudding user response：

The issue was the way you tried to merge the dictionary. Please add it by class name that may resolve the issue.Please refer to this thread:

https://docs.microsoft.com/en-us/answers/questions/310767/issue-with-mergeddictionaries-after-updating-to-xa.html