Question

在我的应用中使用UIPageViewController时，我遇到了一些非常奇怪的行为。在第一次滑动到下一个视图时或者任何时候滑动方向改变（即在列表的末尾并返回），结果视图为空白，我需要再次滑动相同的方向以显示相应的视图。

包含3个视图的示例工作流程：

第一个视图
向右滑动
第二个视图闪烁进出
向右滑动
提出第二个视图
向右滑动
提出第三个观点
向左滑动
第二个视图闪烁进出
向左滑动
提出第二个视图

我注意到当眨眼发生时通过记录（上面的2＆3），事件的顺序如下：

调用GetNextViewController
调用GetPreviousViewController
调用GetNextViewController

然后当我再次滑动时，适当调用GetNextViewController并显示视图。

显然，我的问题是第二个视图应该显示没有闪烁进出。我尝试了各种各样的东西，但没有任何成果。

更新

以下是一个重现问题的示例单控制器应用程序：

using System;
using System.Drawing;

using MonoTouch.Foundation;
using MonoTouch.UIKit;
using System.Collections.Generic;

namespace TestPageView
{
    public partial class TestPageViewViewController : UIViewController
    {
        public TestPageViewViewController () : base ("TestPageViewViewController", null)
        {
        }

        public override void DidReceiveMemoryWarning ()
        {
            // Releases the view if it doesn't have a superview.
            base.DidReceiveMemoryWarning ();

            // Release any cached data, images, etc that aren't in use.
        }

        public override void ViewDidLoad ()
        {
            base.ViewDidLoad ();

            var controllers = new List<UIViewController>
            {
                new TestViewController(View, 1),
                new TestViewController(View, 2),
                new TestViewController(View, 3),
                new TestViewController(View, 4)
            };

            var _pageViewController = new UIPageViewController(UIPageViewControllerTransitionStyle.Scroll, UIPageViewControllerNavigationOrientation.Horizontal);
            var dataSource = new ViewDataSource(controllers);
            _pageViewController.DataSource = dataSource;
            //ViewDataSource has an indexer that returns it's controllers
            _pageViewController.SetViewControllers(new[] { controllers[0] }, UIPageViewControllerNavigationDirection.Forward, false, null);
            View.AddSubview(_pageViewController.View);
        }

        public override bool ShouldAutorotateToInterfaceOrientation (UIInterfaceOrientation toInterfaceOrientation)
        {
            // Return true for supported orientations
            return (toInterfaceOrientation != UIInterfaceOrientation.PortraitUpsideDown);
        }
    }

    public class TestViewController : UIViewController
    {
        private readonly UIView _parent;
        private readonly int _number;
        public TestViewController(UIView parent, int number)
        {
            _parent = parent;
            _number = number;
        }

        public override void ViewDidLoad ()
        {
            base.ViewDidLoad ();

            var textView = new UITextView(_parent.Bounds);
            textView.TextAlignment = UITextAlignment.Center;
            textView.AttributedText = new NSAttributedString(_number.ToString(), UIFont.BoldSystemFontOfSize(18));
            View.Add(textView);
        }
    }

    public class ViewDataSource : UIPageViewControllerDataSource
    {
        private LinkedListNode<UIViewController> current;

        public ViewDataSource(IEnumerable<UIViewController> controllers)
        {
            var controllerLiist = new LinkedList<UIViewController>(controllers);
            current = controllerLiist.First;
        }

        public override UIViewController GetPreviousViewController(UIPageViewController pageViewController, UIViewController referenceViewController)
        {
            if(current.Previous == null){
                Console.WriteLine("returning previous nothing");
                return null;
            }
            Console.WriteLine("returning previous something");
            current = current.Previous;
            return current.Value;
        }

        public override UIViewController GetNextViewController(UIPageViewController pageViewController, UIViewController referenceViewController)
        {
            if(current.Next == null){
                Console.WriteLine("returning next nothing");
                return null;
            }
            Console.WriteLine("returning next something");
            current = current.Next;
            return current.Value;
        }
    }
}

Answer 1

iOS将调用GetPreviousViewController和GetNextViewController两次：首先是当前控制器，第二次是当前控制器的后空翻。

你应该这样做

current = current.Previous;

仅在第一次通话时。

检查referenceViewController以执行此操作：

public override UIViewController GetPreviousViewController (UIPageViewController pageViewController, UIViewController referenceViewController)
    {
        var __c = Pages.Find(referenceViewController);

        if (__c.Previous != null)
            return __c.Previous.Value;
        else
            return null;
    }
    public override UIViewController GetNextViewController (UIPageViewController pageViewController, UIViewController referenceViewController)
    {
        var __c = Pages.Find(referenceViewController);

        if (__c.Next != null)
            return __c.Next.Value;
        else
            return null;
    }

UIPageViewController第二个视图变为空白

1 个答案: