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I have a .NET MAUI app which needs to use native iOS and Android libraries. I created the Android binding library without any issue. When trying to create the iOS binding library, I found that the only reasonable option is to choose "Binding Library" under "Unified API". However, after the binding library project is created, I found that the project structure is a bit different than Xamarin.Forms: There is no Frameworks folder.
The bigger problem is that there is no StructsAndEnums.cs file, only Structs.cs file. But when I used objective sharpie to create bindings, it created two files, ApiDefinition.cs and StructsAndEnums.cs. I can copy the content of the ApiDefinition.cs into the one in the binding library project, but I cannot copy the content of StructsAndEnums.cs into Structs.cs in the binding library project. I think there is a reason it is called Structs.cs, not StructsAndEnums.cs. But there are enum definitions in the StructsAndEnums.cs created in sharpie that are used in ApiDefinition.cs. So I do need StructsAndEnums.cs. I tried to rename Structs.cs to StructsAndEnums.cs and copy the content into it. Still it said the enums didn't exist in the current context.
I use Visual Studio 2022 v17.4 Preview version.
Any help is greatly appreciated!
I found that sharpie didn't always created the contents of the files correctly. So I fixed some errors in the two files. After that, I tried three methods: 1. Leave the file name Structs.cs as-is, 2. Change file name Structs.cs to StructsAndEnums.cs, 3. Move the enum definitions from Structs.cs to ApiDefinition.cs.
In all three cases, I got the same error: BTOUCH: error BI1079: bgen: Do not know how to make a signature for System.SByte* in parameter 'file' from Com.CompanyName.Logger.LogLevel. There is no Logger.LogLevel in the native code. There is only a class method called logLevel with parameters. Is this error caused by inaccurate mapping of sharpie to the native code? If so, I don't even know where to fix this, because there is no Logger.LogLevel in the generated cs code.
When running on Xamarin with VS 2019, there is no such an error.
I was able to solve the problem by changing the sbyte type to string type. Sbyte was set as input parameter's type when objective sharpie was trying to generate ApiDefinition.cs file.
Even though it looks like the iOS binding library build passed. Now I have more serious problems. The project failed to run. The error log is:
The operation failed due to an internal error: Could not load file or assembly 'System.Runtime, Version 7.0.0.0, Culture=neutral, PublicKeyToken=b03...'. The system cannot find the file specified
When this happens, reverting changes back to where only Android binding library was added is not enough even though the app could run when there's only Android binding library included. I have to revert back to where no binding libraries were added.
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The error means the package references are not able to match the version of .NET project, and it looks you are using .Net7 for MAUI. You could check the csproj of your iOS project and compare the TargetFramework .
No, I specifically chose .NET 6.0 for the MAUI project. Later on, when adding Android and iOS binding libraries, there's no choice to choose .NET7.0 or .NET6.0. So I assume they also use .NET6.0. I did a search in the project, and didn't find any keyword net7.0. The csproj file contains this:
<TargetFrameworks> net6.0-android;net6.0-ios;net6.0-maccatalyst</TargetFraemworks>
Also, just after I added iOS binding library and before adding the native reference and changing the content of Structs.cs and ApiDefinition.cs, I built the iOS binding library successfully, and I could remember I also run MAUI without issue.
When build failed, it also said to "See the build log for details". But I couldn't see anywhere that has more details about the failure. The only place I found relevant information is in "Package Console" tab, which showed the error I posted earlier, i.e. The operation failed due to an internal error: Could not load file or assembly 'System.Runtime, Version 7.0.0.0, ...
Now I created a new Maui project and specifically chose .NET 7. After I successfully included and built the iOS binding library project, and then ran the MAUI project, I got the exact same error:
The operation failed due to an internal error: Could not load file or assembly 'System.Runtime, Version 7.0.0.0, Culture=neutral, PublicKeyToken=b03...'. The system cannot find the file specified
The "The operation failed due to an internal error: Could not load file or assembly 'System.Runtime, Version 7.0.0.0,.." does not necessarily occur with a successful inclusion of iOS binding library. It could happen when an Android binding library's csproj file is changed. Here is a case where this happened:
I reverted back to the condition where there's no binding library projects added. Then I copied the Android binding library project into the Maui project, added it as an existing project. Then I built the binding library project. It appeared to build without any errors, and I could also run Maui project. Then, because I saw some build warnings when building the library project (it seemed about GooglePlayServices needs TargetFrameworkVersion to be 11, but I set it to 10), I changed the binding library project's TargetFrameworkVersion to 11. This immediately led to the above mentioned error. Changing it back to 10 didn't solve the issue.
I remember when I first created the binding library project, TargetFrameworkVersion was automatically set to 13. That caused build error, and I had to lower it to build. There's no error at the time.
I think the problem may have something to do with adding the incorrect binding libraries in the project. I think for Android library, I should choose "Android Java Library Binding" under .NET, not "Binding Library" under General. For iOS, it may be "iOS Binding Library" under .NET, not "Binding Library" under Unified API.
With this change, I can see the library projects' csproj file contains: <TargetFramework>net7.0-android</TargetFramework> and <TargetFramework>net7.0-ios</TargetFramework> . Before this change, the csproj files' contents were quite different.
But I would like that the generated library project is based on net6.0, not net7.0, since the Maui project uses net6.0. I cannot find anywhere in the process that give me the option to choose between net6.0 and net7.0. I also tried command line in terminal, but it still gave me a project with net7.0.
For your scenario,it is recommended to open a support ticket for this. Please contact our paid phone support at MS Support.
You will get 1:1 support on that.
Will do. Thank you!
You are welcome.
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Was this successful in the end? I am also doing this but I don't think I can even get as far as you did as I can't even compile. My problem is that BaseType[Attribute] could not be found in the ApiDefinition. This is defined in Xamarin.iOS, but does not seem to be available in .NET7. Even when I create a Bindings project under Unified API (As you mention above) It shows example API code with this attribute.
I feel like I'm missing something here, or am looking for the answer to the wrong question or something. I can't seem to find anyone who has created .NET to iOS bindings which will work in MAUI and not tied to Xamarin.iOS.
False alarm. The ObjcBindingApiDefinition and ObjcBindingCoreSource were missing in the .csproj file. It works now. Very bad that this was missing in the sample/commented template code when creating a bindings project. MAUI has a long way to go!
Did your iOS binding library work eventually? Mine still does not. The problem is that when I conditionally add the binding library as a project dependency for net6.0-ios, it gets add to both net6.0-ios and net6.0-android. The same is true for the Android binding library.
Did your iOS binding library work eventually? Mine still does not. The main problem is that when I conditionally add the binding library as a project dependency for net6.0-ios, it gets added for both net6.0-ios and net6.0-android. The same is true for Android binding library, it gets added for both net6.0-android and net6.0-ios.
That does not seem to be an issue if I only run Android. So I only get Android working.