[huawei_map] 6.12.0+301: custom marker icons from fromAssetImage/fromAsset no longer load (missing flutter_assets/ prefix)

[fleoparra]

Description

After upgrading huawei_map from 6.11.2 to 6.12.0+301, all markers using a custom
icon created with BitmapDescriptor.fromAssetImage(...) (or fromAsset) are no
longer displayed on the map. Markers with the default icon work fine.

Root cause

In 6.12.0+301 the deprecated io.flutter.view.FlutterMain was removed from
android/src/main/java/com/huawei/hms/flutter/map/utils/Convert.java
(toBitmapDescriptor), but the replacement passes the raw Flutter asset path to
BitmapDescriptorFactory.fromAsset(...):

case Param.FROM_ASSET_IMAGE:
    if (data.size() == 3) {
        return BitmapDescriptorFactory.fromAsset(
                Convert.toString(data.get(1)).replaceFirst("^/", ""));
    }

Flutter assets live inside the APK under flutter_assets/, so the lookup for
e.g. assets/img/pin.png fails (it should be flutter_assets/assets/img/pin.png)
and the marker is silently not rendered.

In 6.11.2 this worked because FlutterMain.getLookupKeyForAsset() added the
flutter_assets/ prefix.

Fix

Replace the removed FlutterMain call with the v2-embedding equivalent instead
of the raw path:

import io.flutter.FlutterInjector;
...
return BitmapDescriptorFactory.fromAsset(
        FlutterInjector.instance().flutterLoader().getLookupKeyForAsset(Convert.toString(data.get(1))));

(same change for the three call sites in FROM_ASSET / FROM_ASSET_IMAGE).

I verified this fix on a device: fleoparra@3a8a10b

Environment

• huawei_map: 6.12.0+301 (pub.dev)
• Flutter: Flutter 3.41.9
• Device: ALL Huawei devices with HMS