[Android] Correctly size content after toggling soft keyboard in Resize mode (#927)

* Repro of 45215

* Consolidate base class for Entry/Editor; add missing Dispose implementations

* Fixed problem with hiding the keyboard and child layout in ScrollViewer

* Force page layout update when navigating back from a keyboard-resized page

* Explanatory comments

* Fix namespace

* Fix possible NRE after device rotation

1 files changed, 44 insertions, 0 deletions

diff --git a/Xamarin.Forms.Platform.Android/Renderers/FormsEditText.cs b/Xamarin.Forms.Platform.Android/Renderers/FormsEditText.cs
new file mode 100644
index 00000000..92c3600b
--- /dev/null
+++ b/Xamarin.Forms.Platform.Android/Renderers/FormsEditText.cs
@@ -0,0 +1,44 @@
+using System;
+using Android.Content;
+using Android.Graphics;
+using Android.Views;
+using Android.Widget;
+
+namespace Xamarin.Forms.Platform.Android
+{
+	public class FormsEditText : EditText, IDescendantFocusToggler
+	{
+		DescendantFocusToggler _descendantFocusToggler;
+
+		internal FormsEditText(Context context) : base(context)
+		{
+		}
+
+		bool IDescendantFocusToggler.RequestFocus(global::Android.Views.View control, Func<bool> baseRequestFocus)
+		{
+			_descendantFocusToggler = _descendantFocusToggler ?? new DescendantFocusToggler();
+
+			return _descendantFocusToggler.RequestFocus(control, baseRequestFocus);
+		}
+
+		public override bool OnKeyPreIme(Keycode keyCode, KeyEvent e)
+		{
+			if (keyCode != Keycode.Back || e.Action != KeyEventActions.Down)
+			{
+				return base.OnKeyPreIme(keyCode, e);
+			}
+
+			this.HideKeyboard();
+
+			OnKeyboardBackPressed?.Invoke(this, EventArgs.Empty);
+			return true;
+		}
+
+		public override bool RequestFocus(FocusSearchDirection direction, Rect previouslyFocusedRect)
+		{
+			return (this as IDescendantFocusToggler).RequestFocus(this, () => base.RequestFocus(direction, previouslyFocusedRect));
+		}
+
+		internal event EventHandler OnKeyboardBackPressed;
+	}
+}
\ No newline at end of file