Get current Activity - Xamarin Android

问题

I am developing an portable App for Android and iOS. My current function is taking a Screenshot and use that image in the code. Therefor I have an Interface in the portable library.

public interface IFileSystemService
{
    string GetAppDataFolder();
}

I am taking the Screenshot also in the portable Library with the following code:

static public bool TakeScreenshot()
    {
        try
        {
            byte[] ScreenshotBytes = DependencyService.Get<Interface.IScreenshotManager>().TakeScreenshot();
            return true;
        }
        catch (Exception ex)
        {
        }
        return false;
    }

This either calls the Android or the iOS version.

Android:

class ScreenshotManagerAndroid : IScreenshotManager
{
    public static Activity Activity { get; set; }

    public byte[] TakeScreenshot()
    {

        if (Activity == null)
        {
            throw new Exception("You have to set ScreenshotManager.Activity in your Android project");
        }

        var view = Activity.Window.DecorView;
        view.DrawingCacheEnabled = true;

        Bitmap bitmap = view.GetDrawingCache(true);

        byte[] bitmapData;

        using (var stream = new MemoryStream())
        {
            bitmap.Compress(Bitmap.CompressFormat.Png, 0, stream);
            bitmapData = stream.ToArray();
        }

        return bitmapData;
    }

The question now is to get the current Activity from my app.

回答1:

Since the release of Xamarin 2.5, Xamarin.Forms.Forms.Context is obsolete. The Context can now be obtained as follows:

var currentContext = Android.App.Application.Context;

回答2:

A better way would be to use the Current Activity Plugin. Then you could just do CrossCurrentActivity.Current.Activity.

If you do not want to use a plugin and you only have 1 Activity in your app, you could get away with assigning a static variable in MainActivity and referencing that where ever you needed it like this:

public class MainActivity : FormsApplicationActivity {
    public static Context Context;

    public MainActivity () {
        Context = this;
    }
}

If you needed Context within a custom renderer, you would want to use the Context passed into the constructor, like this:

public class MyEntryRenderer : EntryRenderer {

    private readonly Context _context;

    public MyEntryRenderer(Context context) : base(context) {
        _context = context;
    }

    // Now use _context or ((Activity)_context) any where you need to (just make sure you pass it into the base constructor)
}

The old deprecated way would be var view = ((Activity)Xamarin.Forms.Forms.Context).Window.DecorView;

Xamarin automatically assigns the Activity to Forms.Context.

回答3:

var activity = (Activity)Forms.Context;

or if you are using MainActivity

var activity = (MainActivity)Forms.Context;

来源：https://stackoverflow.com/questions/43279971/get-current-activity-xamarin-android

标签

android

android-activity

Xamarin

xamarin.android