IOS MKMapView capture click event on MKPointAnnotation

[joemockdao]

Hello all, i'm using the code example present on github, which explains how to use maps on IOS with compose multiplatform,
Analyzing the UIKitView to show the MKMapView, I would like to know if there is a possibility to capture the MKPointAnnotation Tap event, to then show, once the markers on the map have been pressed, my custom screen above the Map.
Thanks to whoever will answer me

[dima-avdeev-jb]

Yes, you can handle events on MKMapView.
You need to write Kotlin code that will be similar to the following Swift code:
https://stackoverflow.com/questions/64950827/how-to-call-a-function-or-tell-if-a-mkpointannotation-is-clicked-on-a-mkmapview

[realityexpander]

How will this work with Compose iOS?

I don't see anything in that SO article that addresses the OP's issue.

Using Compose, there is no class or struct to implement a the MKMapViewDelegate... its just a function.

Either I'm missing something, or your answer is non-sensical.

[elijah-semyonov]

Here is a code snippet to give you a general idea how interacting with delegate-based APIs could work in Compose on iOS.

@Composable
fun MapView() {
    var showSomething by remember { mutableStateOf(false) }
    
    UIKitView(factory = {
        val mkMapView = MKMapView()
        
        mkMapView.delegate = object : NSObject(), MKMapViewDelegateProtocol {
            override fun mapView(mapView: MKMapView, didDeselectAnnotation: MKAnnotationProtocol) {
                showSomething = true
            }
        }
        
        mkMapView
    }, Modifier.fillMaxSize())
    
    if (showSomething) {
        ...
    }
}

[realityexpander]

OK, thank you for the suggestion!

I actually tried this early in my discovery phase, but abandoned it because although it compiles with odd warnings, I got stuck with weird run-time issues. Like map doesnt render, callbacks are not fired, and not able to implement more than on method in the delegate... maybe this is just not yet possible, or no one has tried yet?

It seems to be directly related to the iOS code for the interfaces to native iOS functions, and maybe this is not setup properly?

Here is my Github project if you want to look at my code: https://github.com/realityexpander/ContactsComposeMultiplatform

The Compose code in the iosMain/../presentation package.

I am running Android Studio Hedgehog | 2023.1.1 Beta 6 patch 2.

I am finally able to compile and build, but i'm not able to override/implement more than one function in the delegate...

I think this is an issue that can only be solved by addressing the interfaces defined in 3_MapKit.knm ie:

// ...
    @kotlin.commonizer.ObjCCallable public open expect fun mapView(mapView: platform.MapKit.MKMapView, didSelectAnnotationView: platform.MapKit.MKAnnotationView): kotlin.Unit { /* compiled code */ }

    @kotlin.commonizer.ObjCCallable public open expect fun mapView(mapView: platform.MapKit.MKMapView, didDeselectAnnotation: platform.MapKit.MKAnnotationProtocol): kotlin.Unit { /* compiled code */ }
...

Right now, you cannot define more than one override in the delegate:

It seems that the compiler/interface defintions are not allowing for more than one type as the second parameter... IE: you can only have one MKAnnotationProtocol for the second parameter.... this seems like a fundamental issue that needs to be solved by the Kotlin/Native platform MapKit team?

Also, these functions are not being called in response to events.

Works fine in regular SwiftUI.

Also overriding some functions (i triedmapViewDidFinishLoadingMap) in the delegate cause rendering problems:

I'm currently leaning on that this is just not possible yet, the plaform team at IntelliJ needs to address this issue.

What do you think?

[elijah-semyonov]

Yeah, it's indeed a cinterop issue. I'll pass it to the team.
A workaround for now could be to construct those on Obj-C/Swift side and pass it inside the Kotlin world.

[realityexpander]

OK, thanks for verifying this.

I guess I am on the edge of the razor on this... looks like im going to have to wait and see if this get addressed soon.

[realityexpander]

Without access to the code that generates that... im not sure how that is possible...

[bartekpacia]

I've just hit this issue. Is there any guidance on how to override Objective-C methods from Kotlin?

[realityexpander]

That's the problem we are seeing with this issue, yep!

[elijah-semyonov]

Does @Suppress("CONFLICTING_OVERLOADS") help?

[bartekpacia]

This is how I resolved it

Fleet's IntelliSense is still angry and underlines that, but it builds and runs just fine.