Load Pin Image from Resources in Android

[ravero]

SUMMARY

BitmapDescriptorFactory should provide a way from loading Pin Icon from a Resource Drawable. This is important because rendering directly from the Assets folder doesn't take into account the image densities, and would render incorrect size or low quality pin images.

DETAILS

Google Maps Android SDK actually provides a method from loading for loading Marker bitmap from resource.

My suggestion is to add a FromResource method to the BitmapDescriptorFactory class. When rendering on Android, it should call the previously mentioned method to load icon from the Resources. When loaded from other platforms, it should mimics the behaviour of FromBundle, since there's no equivalent of resources in iOS or UWP.

The usage would be as follows:

pin.Icon = BitmapDescriptorFactory.FromResource("resource_name");

PLATFORMS

• [x] Android
• [x] iOS
• [ ] UWP

[amay077]

Hi @ravero , you're correct.

Currently supported icon types are below table.

X.F.GoogleMaps	Android	iOS
Default	defaultMarker	markerImage
Bundle	fromAsset	fromBundle
Stream	fromBitmap	UIImage.LoadFromData
AbsolutePath	fromPath	UiImage.FromFile
N/A	FromResource	N/A

I can't support Android's FromResource because I have 2 reasons.

1. FromResource is only for Android, iOS and UWP can't support it
2. Android's resource Id is number type and auto generate constants(like Resource.Drawable.your_awesome_drawable_1), but these constants can't use in Xamarin.Forms project.

My suggested solution is make your own BitmapDescriptorFactory implemented from IBitmapDescriptorFactory.

ref - https://github.com/amay077/Xamarin.Forms.GoogleMaps/issues/436#issuecomment-430616158

[ravero]

I took the solution of overriding the default BitmapDescriptorFactory, it works but I still think that it's possible to add a built-in solution.

In my project I don't reference the Drawable by it's internal int Id, but by it's name, and I map the Bundle name of the descriptor as the base resource:

context.Resources.GetIdentifier(descriptor.BundleName, "drawable", context.ApplicationInfo.PackageName);

This command resolves the name to the int resource identifier. As I said before, FromResource could be mapped to UIImage.FromFile on iOS, this way we could provide a unified solution.

The required context object to translate name into resource Id could be get from the initialization code requests the context.

To me seems a pretty elegant solution. Maybe we could put that on vote.