Java – how to force an application to create thumbnails (Snapshots) for the list of recent applications?

My application tester reports:

My device uses Android 2.0, so I can't check and debug the problem (the thumbnail in the recent application is since Android 3.0) Therefore, further research is in a "blind mode"

I decided to use oncreatethumbnail() as proposed here to manually force the creation of application thumbnails (in order to simplify the initial task, I didn't catch the real snapshot, but used splashScreen drawable.)

@Override
public boolean onCreateThumbnail(Bitmap outBitmap,Canvas thumbCanvas) {
    super.onCreateThumbnail(outBitmap,thumbCanvas);

    //splashscreen drawable to bitmap
    outBitmap = BitmapFactory.decodeResource(getResources(),R.drawable.titel);

    //automatically scale to provided canvas 
    //(is the canvas provided as input ???)
    thumbCanvas.drawBitmap(outBitmap,new Paint());

    //is the outBitmap itself scaled to canvas or its copy???
    return true;
}

I'm not sure if the above code is correct because I can't test it (see below)

Another possible solution to aligning to docs may be a virtual @ override oncreatethumbnail with only super Oncreatethumbnail(), because the document says:

But the oncreatethumbnail method did not trigger, at least on my Android 2 In fact, this technique is designed for Android 3 Also reported here (year 2012) and also here (year 2009) In both cases, the Android version is not used

Then please help answer the following questions:

1) Does the above code apply to Android 3 devices that use thumbnails in the recent app list?

2) If not, is there any other solution for the application to generate the correct thumbnails (or draw them arbitrarily to my choice)?

Thank you in advance!

Solution

This is an issue with the OS. Unfortunately, it seems useless If you don't want people to see your app recently for some reason, you can

getWindow().addFlags(WindowManager.LayoutParams.FLAG_SECURE)

As the first line of the oncreate () method of the activity