我正在展示一个简单的 UIPageViewController 并向其中添加一些非常简单和愚蠢的 subview Controller 。当 UIPageViewController 被解雇时,我正在处理所有 subview Controller ,当前未显示的(在 ChildViewControllers 中列出)和显示的(在 ViewControllers 中列出)。未显示的被释放,显示的不被释放。
我已将此分解为一个简单的失败测试,因此我确信这与 subview Controller 的内容或其他一些问题无关。我不知道是什么保留了它。
样本:
大师(介绍)
public class MasterDialog : UIPageViewController
{
public event EventHandler OnDialogClosed;
private UIBarButtonItem _backButton;
public MasterDialog() : base(
UIPageViewControllerTransitionStyle.Scroll,
UIPageViewControllerNavigationOrientation.Horizontal,
UIPageViewControllerSpineLocation.None,
25)
{
_backButton = new UIBarButtonItem(UIBarButtonSystemItem.Cancel);
_backButton.Clicked += Close;
NavigationItem.SetLeftBarButtonItem(_backButton, false);
}
public override void ViewDidDisappear(bool animated)
{
base.ViewDidDisappear(animated);
OnDialogClosed(this, EventArgs.Empty);
}
private void Close(object sender, EventArgs arguments)
{
_backButton.Clicked -= Close;
NavigationController.DismissViewController(true, null);
}
protected override void Dispose(bool disposing)
{
base.Dispose(disposing);
Console.WriteLine("Master disposed");
}
}
主数据源
public class DataSource : UIPageViewControllerDataSource
{
public override UIViewController GetPreviousViewController(
UIPageViewController pageViewController, UIViewController referenceViewController)
{
var detail = (DetailDialog)referenceViewController;
if (detail.Page - 1 == 0)
return null;
return GetViewController(detail.Page - 1);
}
public override UIViewController GetNextViewController(
UIPageViewController pageViewController, UIViewController referenceViewController)
{
var detail = (DetailDialog)referenceViewController;
return GetViewController(detail.Page + 1);
}
public UIViewController GetViewController(int page)
{
return new DetailDialog(page);
}
}
细节( child )
public class DetailDialog : UITableViewController
{
public int Page { get; private set; }
public DetailDialog(int page) : base(UITableViewStyle.Plain)
{
Page = page;
}
public override void ViewDidLoad()
{
base.ViewDidLoad();
Console.WriteLine("Detail init: " + Page + " / " + GetHashCode());
var label = new UILabel();
label.Text = "#" + Page;
label.ContentMode = UIViewContentMode.Center;
label.Frame = new System.Drawing.RectangleF(0, 100, 320, 50);
label.BackgroundColor = UIColor.Green;
Add(label);
}
protected override void Dispose(bool disposing)
{
base.Dispose(disposing);
Console.WriteLine("Detail disposed: " + Page + " / " + GetHashCode());
}
}
打开对话框(起点)
public class StartDialog : UIViewController
{
private DataSource _dataSource;
private MasterDialog _master;
public StartDialog()
{
Title = "WTF";
}
public override void ViewDidLoad()
{
base.ViewDidLoad();
var button = new UIButton(UIButtonType.Custom);
button.SetTitle("Open", UIControlState.Normal);
button.BackgroundColor = UIColor.Green;
button.Frame = new System.Drawing.RectangleF(20, 150, 280, 44);
Add(button);
button.TouchDown += OpenMasterDialog;
}
private void OpenMasterDialog(object sender, EventArgs arguments)
{
_dataSource = new DataSource();
_master = new MasterDialog();
_master.DataSource = _dataSource;
_master.OnDialogClosed += HandleOnDialogClosed;
_master.SetViewControllers(
new [] { _dataSource.GetViewController(1) },
UIPageViewControllerNavigationDirection.Forward,
false,
null
);
NavigationController.PresentViewController(
new UINavigationController(_master),
true,
null
);
}
private void HandleOnDialogClosed(object sender, EventArgs e)
{
_dataSource.Dispose();
_dataSource = null;
Console.WriteLine("Before: " + _master.ChildViewControllers.Length +
"/" + _master.ViewControllers.Length + ")");
var childs = _master
.ChildViewControllers.ToList()
.Union(_master.ViewControllers);
foreach (UIViewController child in childs)
{
child.RemoveFromParentViewController();
child.Dispose();
}
Console.WriteLine("After: " + _master.ChildViewControllers.Length +
"/" + _master.ViewControllers.Length + ")");
_master.OnDialogClosed -= HandleOnDialogClosed;
_master.Dispose();
_master = null;
}
}
最佳答案
我可能误解了您的代码/意图,但在这种情况下,在我看来一切都很好。无论如何,这是我的发现......
Detail disposed: 1 / 36217954
After: 0/1)
第 2 行显示
/1
我认为这是问题所在。这是正常的,因为您是 回复 - 显示 View Controller ,IOW 代码:_master.ViewControllers.Length
调用
viewControllers
UIPageViewController
上的选择器.返回:“页面 View Controller 显示的 View Controller 。”仍然是 DetailDialog
那时(即使 master
不再显示)。这不是 Xamarin 特定的,ObjC 应用程序将在同一时间点返回相同的( native )实例。
这已经解释了——但它仍然没有被释放,为什么?
下 new
Dispose
semantics 在 Dispose
之后保留托管对象,只要 native 端需要它(但没有 native 引用,因此它可以被 native 释放,随后在托管端释放)。在这种情况下, 的生命周期原生 对象还没有结束(即 iOS 仍然引用它),所以它在托管端仍然存在。
_master.Dispose();
_master = null;
这将删除 托管 引用
_master
但同样(与上面相同)它不会被释放(也不会是 DetailDialog
)只要 native _master
使用实例(带有 native 引用)。那么谁得到了
_master
的引用? NavigationController.PresentViewController(
new UINavigationController(_master),
^ 这将创建一个
UINavigationController
只要它还活着,就会有对其他人的引用。当我处理
UINavigationController
(我将它保存在一个字段中)然后 Master* 和 Detail* 实例从 HeapShot 中消失。 _nav.Dispose();
_nav = null;
关于ios - UIPageViewController 不会释放最后显示的对话框,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/21147136/