Resize UI after keyboard appears. Issues with dimensions and sizes - ios

Question

I want to resize a UIView (e.g. TextField, UIGridView, ...) after the keyboard appears. Getting the appropriate events isn't the issue. I really stock by calculating the delta to shrink my view depending on the height of the keyboard.
If I have my iPad in front of me in portrait mode all calculations happens as expected. But If my device is in landscape mode or upside down, I'm really struggling getting the right dimensions! Some view frames/bounds aren't converted (in landscape mode is the height still higher then its width). Other views are translated depending if I've started my app already in landscape mode. The next challenge is working with consistent size measures. Sometimes the dimensions are like the real pixels (for a new iPad 2048) sometimes the scale factor isn't considered (for a new iPad 1024).
Any other idea how to the the correct frame size? Or are there any helpers which recognise the current orientation and provides me with the effective sizes?
My current code to achieve my expected behaviour is like this:
MyViewController
public override void ViewWillAppear(bool animated)
{
base.ViewWillAppear(animated);
// My code...
AppDelegate.CurrentDelegate.KeyboardAppeared += KeyboardAppeared;
AppDelegate.CurrentDelegate.KeyboardDisappeared += KeyboardDisappeared;
}
public override void ViewWillDisappear(bool animated)
{
base.ViewWillDisappear(animated);
AppDelegate.CurrentDelegate.KeyboardAppeared -= KeyboardAppeared;
AppDelegate.CurrentDelegate.KeyboardDisappeared -= KeyboardDisappeared;
}
private void KeyboardAppeared(object sender, KeyboardEventArgs e)
{
if (_keyboardButton != null)
_keyboardButton.Enabled = true;
var frame = LayoutHelper.RectangleForKeyboardAppearance(_textField, View.Window, e.Height);
LayoutHelper.ResizeViewForKeyboard(_textField, frame);
}
private void KeyboardDisappeared(object sender, EventArgs e)
{
if (_keyboardButton != null)
_keyboardButton.Enabled = false;
var frame = View.Bounds;
LayoutHelper.ResizeViewForKeyboard(_textField, frame);
}
MyHelperClass
public static RectangleF RectangleForKeyboardAppearance(UIView view, float windowHeight, float keyboardHeight)
{
var topOfKeyboard = windowHeight - keyboardHeight; // Obere linke Ecke der Tastatur auf den Bildschirm bezogen
var viewHeightWindow1 = view.ConvertPointFromView(new PointF(0, topOfKeyboard), null);
var frame = new RectangleF(view.Frame.X, view.Frame.Y, view.Frame.Width, (viewHeightWindow1.Y + view.Bounds.Y));
return frame;
}
public static void ResizeViewForKeyboard(UIView view, RectangleF frame)
{
UIView.BeginAnimations("viewMovementForKeyboard");
UIView.SetAnimationBeginsFromCurrentState(true);
UIView.SetAnimationDuration(0.3f);
view.Frame = frame;
UIView.CommitAnimations();
}