Get Current Activity Xamarin forms

Question

I used Leadtools SDK for Barcode reader , when i try to get current activity it gives me null

This is my code

   Stream resourceStream = new MemoryStream();
        // Droid.MainActivity activity = Forms.Context as Droid.MainActivity;
        var activity = Android.App.Application.Context as Activity;

        int resId = activity.Resources.GetIdentifier("Datamatrix", "drawable", "com.companyname.UDOSE");
     resourceStream = activity.Resources.OpenRawResource(resId);
     var leadStream = LeadStream.Factory.FromStream(resourceStream);
     await ReadBarcode(leadStream);

activity always null , how can i solve this ?

Answer 1

1.define a global static Acitivity,in MainActivity :

public static MainActivity Instance;
protected override void OnCreate(Bundle savedInstanceState)
    {
        TabLayoutResource = Resource.Layout.Tabbar;
        ToolbarResource = Resource.Layout.Toolbar;

        base.OnCreate(savedInstanceState);
        global::Xamarin.Forms.Forms.Init(this, savedInstanceState);       
        Instance = this;
        LoadApplication(new App());
    }

when you use call MainActivity.Instance

2.use the Current Activity Plugin,you could refer to Current Activity

var activity = CrossCurrentActivity.Current.Activity;

3.i suggest you use DependencyService to call the method which was defined in Droid project,like:

create a Interface in sharecode:

public interface IRead
{
    void Read();
}

then in Droid project create a class:

[assembly: Dependency(typeof(AndroidRead))]
namespace Demo.Droid
{
  class AndroidRead:IRead
   {
    public async void Read()
    {
        //here is your codes
        Stream resourceStream = new MemoryStream();
        // Droid.MainActivity activity = Forms.Context as Droid.MainActivity;
        var activity = MainActivity.Instance;

        int resId = activity.Resources.GetIdentifier("Datamatrix", "drawable", "com.companyname.UDOSE");
        resourceStream = activity.Resources.OpenRawResource(resId);
        var leadStream = LeadStream.Factory.FromStream(resourceStream);
        await ReadBarcode(leadStream);
    }
  }
 }

and call in page.xmal.cs like DependencyService.Get<IRead>().Read();

Answer 2

In the Xamarin barcode demo shipped with version 20 of LEADTOOLS, the activity is obtained in MainPage.xaml.cs like this:

...
#elif __ANDROID__
   Stream resourceStream = new MemoryStream();
   var activity = Droid.MainActivity.Instance;
...

Please test with the demo and try this code out on your side and see if it is working.

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