Class does not implement abstract base class member public abstract fun create(p0: Context?, p1: Int, p2: Any?): PlatformView

[wongcheehong]

I have this compile error after following the guide in https://docs.flutter.dev/development/platform-integration/platform-views

I have tried using Flutter v3.0.1 and v2.13.0-0.4.pre to test but still the same error.

Error is shown that:

e: C:\Users\wongc\Documents\Agmo_Studio_Project\ble_poc\android\app\src\main\kotlin\com\example\ble_poc\MapViewFactory.kt: (9, 1): Class 'MapViewFactory' is not abstract and does not implement abstract base class member public abstract fun create(p0: Context?, p1: Int, p2: Any?): PlatformView defined in io.flutter.plugin.platform.PlatformViewFactory
e: C:\Users\wongc\Documents\Agmo_Studio_Project\ble_poc\android\app\src\main\kotlin\com\example\ble_poc\MapViewFactory.kt: (10, 5): 'create' overrides nothing

MainActivity.kt

package com.example.ble_poc

import io.flutter.embedding.android.FlutterActivity
import io.flutter.embedding.engine.FlutterEngine

class MainActivity : FlutterActivity() {
    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        flutterEngine
                .platformViewsController
                .registry
                .registerViewFactory("mappedin", MapViewFactory())
    }
}

MapView.kt

package com.example.ble_poc

import android.content.Context
import android.graphics.Color
import android.view.View
import android.widget.TextView
import io.flutter.plugin.platform.PlatformView

internal class MapView(context: Context, id: Int, creationParams: Map<String?, Any?>?) : PlatformView {
    private val textView: TextView

    override fun getView(): View {
        return textView
    }

    override fun dispose() {}

    init {
        textView = TextView(context)
        textView.textSize = 72f
        textView.setBackgroundColor(Color.rgb(255, 255, 255))
        textView.text = "Rendered on a native Android view (id: $id)"
    }
}

MapViewFactory

package com.example.ble_poc

import android.content.Context
import android.view.View
import io.flutter.plugin.common.StandardMessageCodec
import io.flutter.plugin.platform.PlatformView
import io.flutter.plugin.platform.PlatformViewFactory

class MapViewFactory : PlatformViewFactory(StandardMessageCodec.INSTANCE) {
    override fun create(context: Context, viewId: Int, args: Any?): PlatformView {
        val creationParams = args as Map<String?, Any?>?
        return MapView(context, viewId, creationParams)
    }
}

Is this an error on Flutter side?

[XuanTung95]

I think the create method is changed between Flutter version.
Now it's create(p0: Context?, p1: Int, p2: Any?): PlatformView
Not create(context: Context, viewId: Int, args: Any?): PlatformView

[huycozy]

Hi @wongcheehong, thanks for filing the issue.
I see there's an open issue addressing the case you described.
Closing as duplicate of #98891, so please follow up on it for further updates.

[ilber]

@huycozy I don't think this is a duplicate. The error here is because of this breaking change flutter/engine#31530 introduced in v3.0. It's a really bad change because the context is required to be notNull when dealing with Android views.

[huycozy]

Reopen this issue to investigate this issue further.
Btw, the quick fixes for this might be @XuanTung95's answer

Sample fixes

class MapViewFactory : PlatformViewFactory(StandardMessageCodec.INSTANCE) {
    override fun create(context: Context?, viewId: Int, args: Any?): PlatformView {
        val creationParams = args as Map<String?, Any?>?
        return MapView(context, viewId, creationParams)
    }
}

internal class MapView(context: Context?, id: Int, creationParams: Map<String?, Any?>?) : PlatformView {
    private val textView: TextView

    override fun getView(): View {
        return textView
    }

    override fun dispose() {}

    init {
        textView = TextView(context)
        textView.textSize = 72f
        textView.setBackgroundColor(Color.rgb(255, 255, 255))
        textView.text = "Rendered on a native Android view (id: $id)"
    }
}

[ilber]

That would work if my native control would be a TextView. Unfortunately I am using a FrameLayout, and that one want's a context.

[huycozy]

@ilber,
I can add FrameLayout with Context? as below:

Sample code

internal class MapView(context: Context?, id: Int, creationParams: Map<String?, Any?>?) : PlatformView {
    private lateinit var textView: TextView
    private lateinit var frameLayout: FrameLayout

    override fun getView(): View {
        return frameLayout
    }

    override fun dispose() {}

    init {
        context?.let { ct ->

            textView = TextView(ct)
            textView.textSize = 72f
            textView.text = "Rendered on a native Android view (id: $id)"

            frameLayout = FrameLayout(ct)
            val params = FrameLayout.LayoutParams(
                FrameLayout.LayoutParams.MATCH_PARENT,
                FrameLayout.LayoutParams.MATCH_PARENT)
            frameLayout.setBackgroundColor(Color.GREEN)
            frameLayout.addView(textView, params)
        }

    }
}

Demo

@wongcheehong: you can try the above quick fixes as a temporary solution.

Anw, this issue is reproducible on latest stable and master channels with sample code in https://docs.flutter.dev/development/platform-integration/platform-views

flutter doctor -v

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[ilber]

Hey @huycozy , this is what I did in the end. Thanks a lot for helping us here. It doesn't look nice but it is a valid workaround. I was just curious to know why this change was introduced. With this change we cannot support older and newer versions of flutter.

[ilber]

In order to be compatible also with older versions of Flutter, I have create a java class that extends PlatformViewFactory.

public class AndroidPlatformViewFactory extends PlatformViewFactory {
    public AndroidPlatformViewFactory() {
        super(StandardMessageCodec.INSTANCE);
    }

    @NonNull
    @Override
    public PlatformView create(Context context, int viewId, @Nullable Object args) {
        return new CustomNativeView(context);
    }
}

Here I just removed the @nullable annotation. everything works fine like this. It builds and works with both, old and new versions of Flutter.

[XuanTung95]

@huycozy I don't think this is a duplicate. The error here is because of this breaking change flutter/engine#31530 introduced in v3.0. It's a really bad change because the context is required to be notNull when dealing with Android views.

There is a chance @Nullable Context is a bug. We should ask the developer for confirmation.
cc @blasten

[ilber]

I have already asked but no reply yet.

[blasten]

This will be fixed in flutter/engine#33599

[wangmir]

In order to be compatible also with older versions of Flutter, I have create a java class that extends PlatformViewFactory.

public class AndroidPlatformViewFactory extends PlatformViewFactory {
    public AndroidPlatformViewFactory() {
        super(StandardMessageCodec.INSTANCE);
    }

    @NonNull
    @Override
    public PlatformView create(Context context, int viewId, @Nullable Object args) {
        return new CustomNativeView(context);
    }
}

Here I just removed the @nullable annotation. everything works fine like this. It builds and works with both, old and new versions of Flutter.

Can u elaborate more about this? I'm now struggling with this issue too, and I think u may be able to save me... How can i use this java to connect with former factory? Can i just extend AndroidPlatformViewFactory rather than PlatformViewFactory?

[ilber]

Hey @wangmir , In the class I have pasted, you can just replace the CustomNativeView with your PlatformView and then you register the view factory as follows:

binding.platformViewRegistry.registerViewFactory(
                "id-of-the-platform-view",
                AndroidPlatformViewFactory()
            )

[wangmir]

Hey @wangmir , In the class I have pasted, you can just replace the CustomNativeView with your PlatformView and then you register the view factory as follows:

binding.platformViewRegistry.registerViewFactory(
                "id-of-the-platform-view",
                AndroidPlatformViewFactory()
            )

@ilber Oh, ok thanks I understood. Thanks. This issue saves me a lot..

[Waylon-Firework]

There is another place. In the flutter 2 version, there is a "?" here but not in flutter 3.