Xamarin iOS 内存泄漏无处不在 [英] Xamarin iOS memory leaks everywhere
问题描述
过去 8 个月，我们一直在使用 Xamarin iOS，并开发了一个具有许多屏幕、功能和嵌套控件的重要企业应用程序.我们已经完成了自己的 MVVM 架构、跨平台 BLL 和DAL 为推荐".我们在 Android 之间共享代码，甚至我们的 BLL/DAL 也用于我们的网络产品.
We've been using Xamarin iOS for the last 8 months and developed a non-trivial enterprise app with many screens, features, nested controls. We've done our own MVVM arch, cross platform BLL & DAL as "recommended". We share code between Android and even our BLL/DAL is used on our web product.
一切都很好，除了现在在项目的发布阶段，我们发现基于 Xamarin iOS 的应用程序中到处都是不可修复的内存泄漏.我们已遵循所有指南"来解决此问题，但实际情况是 C# GC 和 Obj-C ARC 似乎是不兼容的垃圾收集机制，它们在单点触控平台中相互重叠.
All is good except now in release phase of project we discover irreparable memory leaks everywhere in the Xamarin iOS-based app. We've followed all the "guidelines" to resolve this but the reality is that C# GC and Obj-C ARC appear to be incompatible garbage collection mechanisms in the current way they overlay each other in monotouch platform.
我们发现的现实是，对于任何非平凡的应用程序，本机对象和托管对象之间的硬循环将发生并且频繁发生.例如，在使用 lambda 或手势识别器的任何地方都非常容易发生这种情况.加上 MVVM 的复杂性，这几乎是一个保证.错过其中一种情况，整个对象图将永远不会被收集.这些图形会引诱其他物体进入并像癌症一样生长，最终导致 iOS 迅速而无情的消灭.
The reality we've found is that hard cycles between native objects and managed objects WILL occur and FREQUENTLY for any non-trivial app. It's extremely easy for this to happen anywhere you use lambdas or gesture recognizers for example. Add in the complexity of MVVM and it's almost a guarantee. Miss just one of these situations and entire graphs of objects will never get collected. These graphs will lure other objects in and grow like a cancer, eventually resulting in a prompt and merciless extermination by iOS.
Xamarin 的回答是对问题的无兴趣推迟以及开发人员应该避免这些情况"的不切实际的期望.对此的仔细考虑表明，这是承认垃圾收集在 Xamarin 中基本上已损坏.
Xamarin's answer is an uninterested deferral of the issue and an unrealistic expectation that "devs should avoid these situations". Careful consideration of this reveals this as an admission that Garbage Collection is essentially broken in Xamarin.
我现在意识到，在传统的 c# .NET 意义上，您并没有真正在 Xamarin iOS 中获得垃圾收集".您需要采用垃圾维护"模式来真正让 GC 移动并完成其工作，即使如此，它也永远不会完美 - 非确定性.
The realization for me now is that you don't really get "garbage collection" in Xamarin iOS in the traditional c# .NET sense. You need employ "garbage maintanence" patterns actually get the GC moving and doing its job, and even then it'll never be perfect - NON DETERMINISTIC.
我的公司投入了大量资金试图阻止我们的应用程序崩溃和/或内存不足.我们基本上必须明确和递归地处理眼前的所有该死的东西，并将垃圾维护模式实施到应用程序中，只是为了阻止崩溃并拥有我们可以出售的可行产品.我们的客户是支持和宽容的，但我们知道这不能永远保持下去.我们希望 Xamarin 有一个专门的团队来处理这个问题，并一劳永逸地解决这个问题.不幸的是，看起来不像.
My company has invested a fortune trying to stop our app from crashing and/or running out of memory. We've basically had to explicitly and recursively dispose every damn thing in sight and implement garbage maintanence patterns into the app, just to stop the crashes and have a viable product we can sell. Our customers are supportive and tolerant, but we know this cannot hold forever. We are hoping Xamarin have a dedicated team working on this issue and get it nailed once and for all. Doesn't look like it, unfortunately.
问题是，对于用 Xamarin 编写的非平凡企业级应用程序，我们的经验是例外还是规则?
Question is, is our experience the exception or the rule for non-trivial enterprise-class apps written in Xamarin?
更新
查看 DisposeEx 方法和解决方案的答案.
See answer for DisposeEx method and solution.
推荐答案
我使用了以下扩展方法来解决这些内存泄漏问题.想想 Ender's Game 最后的战斗场景，DisposeEx 方法就像那道激光，它分离所有视图及其连接的对象，并以一种不会使您的应用程序崩溃的方式递归处理它们.
I used the below extension methods to solve these memory leak issues. Think of Ender's Game final battle scene, the DisposeEx method is like that laser and it disassociates all views and their connected objects and disposes them recursively and in a way that shouldn't crash your app.
当您不再需要该视图控制器时，只需在 UIViewController 的主视图上调用 DisposeEx() 即可.如果某些嵌套的 UIView 有特殊的东西要处理，或者您不想处理它，请实现 ISpecialDisposable.SpecialDispose，它会代替 IDisposable.Dispose 调用.
Just call DisposeEx() on UIViewController's main view when you no longer need that view controller. If some nested UIView has special things to dispose, or you dont want it disposed, implement ISpecialDisposable.SpecialDispose which is called in place of IDisposable.Dispose.
注意:这假设您的应用中没有共享 UIImage 实例.如果是，请修改 DisposeEx 以智能处理.
NOTE: this assumes no UIImage instances are shared in your app. If they are, modify DisposeEx to intelligently dispose.
public static void DisposeEx(this UIView view) {
const bool enableLogging = false;
try {
if (view.IsDisposedOrNull())
return;
var viewDescription = string.Empty;
if (enableLogging) {
viewDescription = view.Description;
SystemLog.Debug("Destroying " + viewDescription);
}
var disposeView = true;
var disconnectFromSuperView = true;
var disposeSubviews = true;
var removeGestureRecognizers = false; // WARNING: enable at your own risk, may causes crashes
var removeConstraints = true;
var removeLayerAnimations = true;
var associatedViewsToDispose = new List<UIView>();
var otherDisposables = new List<IDisposable>();
if (view is UIActivityIndicatorView) {
var aiv = (UIActivityIndicatorView)view;
if (aiv.IsAnimating) {
aiv.StopAnimating();
}
} else if (view is UITableView) {
var tableView = (UITableView)view;
if (tableView.DataSource != null) {
otherDisposables.Add(tableView.DataSource);
}
if (tableView.BackgroundView != null) {
associatedViewsToDispose.Add(tableView.BackgroundView);
}
tableView.Source = null;
tableView.Delegate = null;
tableView.DataSource = null;
tableView.WeakDelegate = null;
tableView.WeakDataSource = null;
associatedViewsToDispose.AddRange(tableView.VisibleCells ?? new UITableViewCell[0]);
} else if (view is UITableViewCell) {
var tableViewCell = (UITableViewCell)view;
disposeView = false;
disconnectFromSuperView = false;
if (tableViewCell.ImageView != null) {
associatedViewsToDispose.Add(tableViewCell.ImageView);
}
} else if (view is UICollectionView) {
var collectionView = (UICollectionView)view;
disposeView = false;
if (collectionView.DataSource != null) {
otherDisposables.Add(collectionView.DataSource);
}
if (!collectionView.BackgroundView.IsDisposedOrNull()) {
associatedViewsToDispose.Add(collectionView.BackgroundView);
}
//associatedViewsToDispose.AddRange(collectionView.VisibleCells ?? new UICollectionViewCell[0]);
collectionView.Source = null;
collectionView.Delegate = null;
collectionView.DataSource = null;
collectionView.WeakDelegate = null;
collectionView.WeakDataSource = null;
} else if (view is UICollectionViewCell) {
var collectionViewCell = (UICollectionViewCell)view;
disposeView = false;
disconnectFromSuperView = false;
if (collectionViewCell.BackgroundView != null) {
associatedViewsToDispose.Add(collectionViewCell.BackgroundView);
}
} else if (view is UIWebView) {
var webView = (UIWebView)view;
if (webView.IsLoading)
webView.StopLoading();
webView.LoadHtmlString(string.Empty, null); // clear display
webView.Delegate = null;
webView.WeakDelegate = null;
} else if (view is UIImageView) {
var imageView = (UIImageView)view;
if (imageView.Image != null) {
otherDisposables.Add(imageView.Image);
imageView.Image = null;
}
} else if (view is UIScrollView) {
var scrollView = (UIScrollView)view;
// Comment out extension method
//scrollView.UnsetZoomableContentView();
}
var gestures = view.GestureRecognizers;
if (removeGestureRecognizers && gestures != null) {
foreach(var gr in gestures) {
view.RemoveGestureRecognizer(gr);
gr.Dispose();
}
}
if (removeLayerAnimations && view.Layer != null) {
view.Layer.RemoveAllAnimations();
}
if (disconnectFromSuperView && view.Superview != null) {
view.RemoveFromSuperview();
}
var constraints = view.Constraints;
if (constraints != null && constraints.Any() && constraints.All(c => c.Handle != IntPtr.Zero)) {
view.RemoveConstraints(constraints);
foreach(var constraint in constraints) {
constraint.Dispose();
}
}
foreach(var otherDisposable in otherDisposables) {
otherDisposable.Dispose();
}
foreach(var otherView in associatedViewsToDispose) {
otherView.DisposeEx();
}
var subViews = view.Subviews;
if (disposeSubviews && subViews != null) {
subViews.ForEach(DisposeEx);
}
if (view is ISpecialDisposable) {
((ISpecialDisposable)view).SpecialDispose();
} else if (disposeView) {
if (view.Handle != IntPtr.Zero)
view.Dispose();
}
if (enableLogging) {
SystemLog.Debug("Destroyed {0}", viewDescription);
}
} catch (Exception error) {
SystemLog.Exception(error);
}
}
public static void RemoveAndDisposeChildSubViews(this UIView view) {
if (view == null)
return;
if (view.Handle == IntPtr.Zero)
return;
if (view.Subviews == null)
return;
view.Subviews.ForEach(RemoveFromSuperviewAndDispose);
}
public static void RemoveFromSuperviewAndDispose(this UIView view) {
view.RemoveFromSuperview();
view.DisposeEx();
}
public static bool IsDisposedOrNull(this UIView view) {
if (view == null)
return true;
if (view.Handle == IntPtr.Zero)
return true;;
return false;
}
public interface ISpecialDisposable {
void SpecialDispose();
}
这篇关于Xamarin iOS 内存泄漏无处不在的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
