Monotouch 移动位于键盘下的内容，自动滚动被键盘遮住的内容

IOS官方的Object-C有例子，但是OC的代码。Moving Content That Is Located Under the Keyboard

效果如下图：

实现方法：

1.定义一个所有ViewControl的基类，命名为ViewControllerBase，ViewControl继承ViewControllerBase

代码如下：

 

public class ViewControllerBase : UIViewController
{
    NSObject _keyboardObserverWillShow;
    NSObject _keyboardObserverWillHide;

    public ViewControllerBase()
    {
    }
    public ViewControllerBase(IntPtr handle) : base(handle)
    {

    }

    public override void ViewDidLoad()
    {
        //设置键盘事件处理程序
        RegisterForKeyboardNotifications();
    }

    protected virtual void RegisterForKeyboardNotifications()
    {
        _keyboardObserverWillShow = NSNotificationCenter.DefaultCenter.AddObserver
            (UIKeyboard.WillShowNotification, KeyboardWillShowNotification);

        _keyboardObserverWillHide = NSNotificationCenter.DefaultCenter.AddObserver
            (UIKeyboard.WillHideNotification, KeyboardWillHideNotification);
    }

    protected virtual void UnregisterKeyboardNotifications()
    {
        NSNotificationCenter.DefaultCenter.RemoveObserver(_keyboardObserverWillShow);
        NSNotificationCenter.DefaultCenter.RemoveObserver(_keyboardObserverWillHide);
    }

    protected virtual UIView KeyboardGetActiveView()
    {
        return this.View.FindFirstResponder();
    }

    protected virtual void KeyboardWillShowNotification(NSNotification notification)
    {
        UIView activeView = KeyboardGetActiveView();
        if (activeView == null)
            return;

        UIScrollView scrollView = activeView.FindSuperviewOfType(this.View, typeof(UIScrollView)) as UIScrollView;
        if (scrollView == null)
            return;

        RectangleF keyboardBounds = UIKeyboard.BoundsFromNotification(notification);

        UIEdgeInsets contentInsets = new UIEdgeInsets(0.0f, 0.0f, keyboardBounds.Size.Height, 0.0f);
        scrollView.ContentInset = contentInsets;
        scrollView.ScrollIndicatorInsets = contentInsets;

        RectangleF viewRectAboveKeyboard = new RectangleF(this.View.Frame.Location,
            new SizeF(this.View.Frame.Width, this.View.Frame.Size.Height - keyboardBounds.Size.Height));

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

        if (!viewRectAboveKeyboard.Contains(activeFieldAbsoluteFrame))
        {
            PointF scrollPoint = new PointF(0.0f,
                activeFieldAbsoluteFrame.Location.Y + activeFieldAbsoluteFrame.Height
                + scrollView.ContentOffset.Y - viewRectAboveKeyboard.Height);
            scrollView.SetContentOffset(scrollPoint, true);
        }
    }

    protected virtual void KeyboardWillHideNotification(NSNotification notification)
    {
        UIView activeView = KeyboardGetActiveView();
        if (activeView == null)
            return;

        UIScrollView scrollView = activeView.FindSuperviewOfType(this.View, typeof(UIScrollView)) as UIScrollView;
        if (scrollView == null)
            return;

        double animationDuration = UIKeyboard.AnimationDurationFromNotification(notification);
        UIEdgeInsets contentInsets = new UIEdgeInsets(0.0f, 0.0f, 0.0f, 0.0f);
        UIView.Animate(animationDuration, delegate
        {
            scrollView.ContentInset = contentInsets;
            scrollView.ScrollIndicatorInsets = contentInsets;
        });
    }
}

2.定义UIView的扩展方法

 

代码如下：

public static class ViewExtensions
{
    public static UIView FindFirstResponder(this UIView view)
    {
        if (view.IsFirstResponder)
        {
            return view;
        }
        foreach (UIView subView in view.Subviews)
        {
            var firstResponder = subView.FindFirstResponder();
            if (firstResponder != null)
                return firstResponder;
        }
        return null;
    }

    public static UIView FindSuperviewOfType(this UIView view, UIView stopAt, Type type)
    {
        if (view.Superview != null)
        {
            if (type.IsAssignableFrom(view.Superview.GetType()))
            {
                return view.Superview;
            }

            if (view.Superview != stopAt)
                return view.Superview.FindSuperviewOfType(stopAt, type);
        }

        return null;
    }
}

实现的效果：

作者：Bruce Lee
出处：http://www.cnblogs.com/BruceLee521
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