1: public class ViewControllerBase : UIViewController

   2: {

   3:     NSObject _keyboardObserverWillShow;

   4:     NSObject _keyboardObserverWillHide;

   5:  

   6:     public ViewControllerBase()

   7:     {

   8:     }

   9:     public ViewControllerBase(IntPtr handle) : base(handle)

  10:     {

  11:  

  12:     }

  13:  

  14:     public override void ViewDidLoad()

  15:     {

  16:         //设置键盘事件处理程序

  17:         RegisterForKeyboardNotifications();

  18:     }

  19:  

  20:     protected virtual void RegisterForKeyboardNotifications()

  21:     {

  22:         _keyboardObserverWillShow = NSNotificationCenter.DefaultCenter.AddObserver

  23:             (UIKeyboard.WillShowNotification, KeyboardWillShowNotification);

  24:  

  25:         _keyboardObserverWillHide = NSNotificationCenter.DefaultCenter.AddObserver

  26:             (UIKeyboard.WillHideNotification, KeyboardWillHideNotification);

  27:     }

  28:  

  29:     protected virtual void UnregisterKeyboardNotifications()

  30:     {

  31:         NSNotificationCenter.DefaultCenter.RemoveObserver(_keyboardObserverWillShow);

  32:         NSNotificationCenter.DefaultCenter.RemoveObserver(_keyboardObserverWillHide);

  33:     }

  34:  

  35:     protected virtual UIView KeyboardGetActiveView()

  36:     {

  37:         return this.View.FindFirstResponder();

  38:     }

  39:  

  40:     protected virtual void KeyboardWillShowNotification(NSNotification notification)

  41:     {

  42:         UIView activeView = KeyboardGetActiveView();

  43:         if (activeView == null)

  44:             return;

  45:  

  46:         UIScrollView scrollView = activeView.FindSuperviewOfType(this.View, typeof(UIScrollView)) as UIScrollView;

  47:         if (scrollView == null)

  48:             return;

  49:  

  50:         RectangleF keyboardBounds = UIKeyboard.BoundsFromNotification(notification);

  51:  

  52:         UIEdgeInsets contentInsets = new UIEdgeInsets(0.0f, 0.0f, keyboardBounds.Size.Height, 0.0f);

  53:         scrollView.ContentInset = contentInsets;

  54:         scrollView.ScrollIndicatorInsets = contentInsets;

  55:  

  56:         RectangleF viewRectAboveKeyboard = new RectangleF(this.View.Frame.Location,

  57:             new SizeF(this.View.Frame.Width, this.View.Frame.Size.Height - keyboardBounds.Size.Height));

  58:  

  59:         RectangleF activeFieldAbsoluteFrame = activeView.Superview.ConvertRectToView(activeView.Frame, this.View);

  60:  

  61:         if (!viewRectAboveKeyboard.Contains(activeFieldAbsoluteFrame))

  62:         {

  63:             PointF scrollPoint = new PointF(0.0f, 

  64:                 activeFieldAbsoluteFrame.Location.Y + activeFieldAbsoluteFrame.Height

  65:                 + scrollView.ContentOffset.Y - viewRectAboveKeyboard.Height);

  66:             scrollView.SetContentOffset(scrollPoint, true);

  67:         }

  68:     }

  69:  

  70:     protected virtual void KeyboardWillHideNotification(NSNotification notification)

  71:     {

  72:         UIView activeView = KeyboardGetActiveView();

  73:         if (activeView == null)

  74:             return;

  75:  

  76:         UIScrollView scrollView = activeView.FindSuperviewOfType(this.View, typeof(UIScrollView)) as UIScrollView;

  77:         if (scrollView == null)

  78:             return;

  79:  

  80:         double animationDuration = UIKeyboard.AnimationDurationFromNotification(notification);

  81:         UIEdgeInsets contentInsets = new UIEdgeInsets(0.0f, 0.0f, 0.0f, 0.0f);

  82:         UIView.Animate(animationDuration, delegate

  83:         {

  84:             scrollView.ContentInset = contentInsets;

  85:             scrollView.ScrollIndicatorInsets = contentInsets;

  86:         });

  87:     }

  88: }

   1: public static class ViewExtensions

   2: {

   3:     public static UIView FindFirstResponder(this UIView view)

   4:     {

   5:         if (view.IsFirstResponder)

   6:         {

   7:             return view;

   8:         }

   9:         foreach (UIView subView in view.Subviews)

  10:         {

  11:             var firstResponder = subView.FindFirstResponder();

  12:             if (firstResponder != null)

  13:                 return firstResponder;

  14:         }

  15:         return null;

  16:     }

  17:  

  18:     public static UIView FindSuperviewOfType(this UIView view, UIView stopAt, Type type)

  19:     {

  20:         if (view.Superview != null)

  21:         {

  22:             if (type.IsAssignableFrom(view.Superview.GetType()))

  23:             {

  24:                 return view.Superview;

  25:             }

  26:  

  27:             if (view.Superview != stopAt)

  28:                 return view.Superview.FindSuperviewOfType(stopAt, type);

  29:         }

  30:  

  31:         return null;

  32:     }

  33: }