在 Xamarin.Forms 中使用 Android 绑定

Question

I am trying to build an app with Xamarin.Forms. I want to use Google ML Kit, so I found a binding for Android.

I was able to import the reference into the Android part of the Xamarin.Forms solution and would like to use it in the code behind the UI.

But in the in project, when I do using Xamarin.Firebase.ML.Vision; I get an error of course, because the reference is in the in.Android project. Am I trying to do something that is anti-pattern in Xamarin?

Answer 1

Xamarin.Firebase.ML.Vision is a Xamarin.Android specific library. it doesn't exist for Xamarin.Forms . As mentioned you need to use the DependencyService to spin up a platform specific implementation. In this case, an Activity that implements the Xamarin.Firebase.ML.Vision code you need.

public interface IVisionImplementer
{
    void StartActivity();
}

Then in your Xamarin.Android project.

[assembly: Dependency(typeof(VisionImplementer))]
public class VisionImplementer : IVisionImplementer
{
    public void StartActivity()
    {
        ///FirebaseActivity is where you will implement the actual vision code you're trying to implement.
        var intent = new Intent(Android.App.Application.Context, typeof(FirebaseVisionActivity))
        intent.SetFlags(ActivityFlags.NewTask);
        Android.App.Application.Context.StartActivity(intent);

To use from Xamarin.Forms use:

var visionImplementer = DependencyService.Get<IVisionImplementer>();
visionImplementer.StartActivity();

That's it. There is also library for iOS so you can do the same thing for your iOS project.