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using System;
using UIKit;
using PointF = CoreGraphics.CGPoint;
using RectangleF = CoreGraphics.CGRect;
namespace Xamarin.Forms.Platform.iOS
{
internal class KeyboardInsetTracker : IDisposable
{
readonly Func<UIWindow> _fetchWindow;
readonly Action<PointF> _setContentOffset;
readonly Action<UIEdgeInsets> _setInsetAction;
readonly UIView _targetView;
bool _disposed;
RectangleF _lastKeyboardRect;
public KeyboardInsetTracker(UIView targetView, Func<UIWindow> fetchWindow, Action<UIEdgeInsets> setInsetAction) : this(targetView, fetchWindow, setInsetAction, null)
{
}
public KeyboardInsetTracker(UIView targetView, Func<UIWindow> fetchWindow, Action<UIEdgeInsets> setInsetAction, Action<PointF> setContentOffset)
{
_setContentOffset = setContentOffset;
_targetView = targetView;
_fetchWindow = fetchWindow;
_setInsetAction = setInsetAction;
KeyboardObserver.KeyboardWillShow += OnKeyboardShown;
KeyboardObserver.KeyboardWillHide += OnKeyboardHidden;
}
public void Dispose()
{
if (_disposed)
return;
_disposed = true;
KeyboardObserver.KeyboardWillShow -= OnKeyboardShown;
KeyboardObserver.KeyboardWillHide -= OnKeyboardHidden;
}
//This method allows us to update the insets if the Frame changes
internal void UpdateInsets()
{
//being called from LayoutSubviews but keyboard wasn't shown yet
if (_lastKeyboardRect.IsEmpty)
return;
var window = _fetchWindow();
// Code left verbose to make its operation more obvious
if (window == null)
{
// we are not currently displayed and can safely ignore this
// most likely this renderer is on a page which is currently not displayed (e.g. in NavController)
return;
}
var field = _targetView.FindFirstResponder();
//the view that is triggering the keyboard is not inside our UITableView?
//if (field == null)
// return;
var boundsSize = _targetView.Frame.Size;
//since our keyboard frame is RVC CoordinateSpace, lets convert it to our targetView CoordinateSpace
var rect = _targetView.Superview.ConvertRectFromView(_lastKeyboardRect, null);
//let's see how much does it cover our target view
var overlay = RectangleF.Intersect(rect, _targetView.Frame);
_setInsetAction(new UIEdgeInsets(0, 0, overlay.Height, 0));
if (field is UITextView && _setContentOffset != null)
{
var keyboardTop = boundsSize.Height - overlay.Height;
var fieldPosition = field.ConvertPointToView(field.Frame.Location, _targetView.Superview);
var fieldBottom = fieldPosition.Y + field.Frame.Height;
var offset = fieldBottom - keyboardTop;
if (offset > 0)
_setContentOffset(new PointF(0, offset));
}
}
void OnKeyboardHidden(object sender, UIKeyboardEventArgs args)
{
_setInsetAction(new UIEdgeInsets(0, 0, 0, 0));
_lastKeyboardRect = RectangleF.Empty;
}
void OnKeyboardShown(object sender, UIKeyboardEventArgs args)
{
_lastKeyboardRect = args.FrameEnd;
UpdateInsets();
}
}
}
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