Xamarin

Xamarin.UWP: Image from embedded resource throws “Operation is not supported on this platform” error

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If you are getting the error “Operation is not supported on this platform” when you are trying to set an ImageResource from file for an image on Xamarin.UWP, then the problem comes from this line of code:

IconSource = ImageSource.FromResource("afolder.animage.jpg");

The solution: Image as Embadded Ressource shows “operation is not supported on this platform” in UWP and Release (microsoft.com)
In a short brief: You need to use the second parameter for FromResource method call. You must pass an assembly in order to success on UWP platform. iOS and Android is not affected with this error.

IconSource = ImageSource.FromResource("afolder.animage.jpg", typeof(AClassFromTheAssembly).Assembly);
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Xamarin.UWP DryIoC error: Code generation not supported on this platform

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If you are getting the following error when using DryIoC with Xamarin.Forms on UWP:

System.PlatformNotSupportedException: Dynamic code generation is not
supported on this platform.
at System.Reflection.Emit. TypeBuilder.GetMethod (Type, Methodinfo) + 0x2d
at
Dryloc.FastExpressionCompiler.LightExpression.ExpressionCompiler.CompileNoA
rgsNew(Constructorlnfo, Type, Type[, Type) + 0x5b
at
Dryloc.FastExpressionCompiler.LightExpression.ExpressionCompiler.TryCompileB
oundToFirstClosureParam(Type, Expression, IParameterProvider, Typel, Type.
CompilerFlags) + 0x73
at Dryloc.FactoryDelegateCompiler.CompileToFactoryDelegate(Expression.
Boolean) + 0x14c
at Dryloc.Container.Dryloc.IResolver.Resolve(Type, IfUnresolved) + 0x23c

Then instantiate your container with this code:

Container = new Container(rules =>
{
    // https://github.com/dadhi/DryIoc/blob/master/docs/DryIoc.Docs/ResolutionPipeline.md
    return rules.WithUseInterpretation();
});

The reason why you need to do this is here: DryIoc/ResolutionPipeline.md at master · dadhi/DryIoc · GitHub

This content has 2 years. Some of the information in this post may be out of date or no longer work. Please, read this page keeping its age in your mind.

Xamarin.Forms: Android app forgets the style when using DynamicResource

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If you break the look and feel of the app when you switch apps on mobile, and you use styles as DynamicResources, which you add as MergedDictionaries in App.Xaml,
you should pay attention to this:

When you don’t exit the Android app, but bring it back to the foreground after a very long time, the constructor logic in App.xaml.cs runs again. Don’t forget to add MergedDictionary from code, which contains the styles. If you forget this, all controls will appear in the app with their default look.

I wrote about how to handle restarting the application here: https://www.banditoth.hu/2021/03/22/xamarin-forms-reopening-application-best-pratices/

This content has 2 years. Some of the information in this post may be out of date or no longer work. Please, read this page keeping its age in your mind.

Xamarin.Forms : Focus to the entry and set the cursor after the last character

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If you want to make the cursor in Xamarin.Forms Entry blink behind the text you have already typed, instead of in front of it, after focusing, you need to do the following:

Subscribe to the Focused event of the Entry and modify the eventhandler as follows:

		public void OnEntryFocused(object sender, EventArgs args)
		{
			EntryInstance.CursorPosition = EntryInstance?.Text?.Length ?? 0;
		}

You can find more information about the CursorPosition at: https://docs.microsoft.com/en-us/dotnet/api/xamarin.forms.entry.cursorposition?view=xamarin-forms

This content has 2 years. Some of the information in this post may be out of date or no longer work. Please, read this page keeping its age in your mind.

Xamarin.Android get resource id without ResourceManager.

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If calling ResourceManager.GetResource(“resourceName”) doesn’t work because the framework doesn’t return the resource you want, you can bypass it with the following code snippet:

            string audioFileNameWithoutExtension = System.IO.Path.GetFileNameWithoutExtension(audiofile);
            int audioResourceId = (int)typeof(Resource.Raw).GetField(audioFileNameWithoutExtension).GetValue(null);
            Android.Net.Uri audioUri = Android.Net.Uri.Parse(ContentResolver.SchemeAndroidResource + "://" + Application.Context.PackageName + "/" + audioResourceId);

            channel.SetSound(audioUri, audioAttributes);

I used this code snippet to set a custom push notification sound

This content has 2 years. Some of the information in this post may be out of date or no longer work. Please, read this page keeping its age in your mind.