IOSLauncher:
@Override
    public void iosShare() {
        GLKView glkView = ((GLKView) ((IOSApplication) Gdx.app).getUIViewController().getView());
        glkView.getDrawableMultisample();
        UIImage image = glkView.getSnapshot();

        NSArray<NSObject> imageArray = new NSArray<NSObject>(image);
        UIActivityViewController share = new UIActivityViewController(imageArray,null);
        ((IOSApplication)Gdx.app).getUIViewController().presentViewController(share, true, null);

        //NSData data = image.toPNGData();
        //data.write(, true);
    }

____________
Calling the method:
public class SomeClass implements Screen

show()
btnShare.addListener(new ChangeListener() {
            @Override
            public void changed(ChangeEvent event, Actor actor) {

                    pInt.iosShare();
            }
        });