c# - 连接仪器时 NSActionDispatcher 被垃圾收集

Question

我正在尝试向我的 iOS 应用程序添加一个计时器，为此我使用以下代码：

using System;
using System.Drawing;
using MonoTouch.Foundation;
using MonoTouch.UIKit;

namespace MyNamespace
{
    [Register ("AppDelegate")]
    public partial class AppDelegate : UIApplicationDelegate
    {
        UIWindow window;
        public static NavigationController MyNavigationController;

        public override bool FinishedLaunching (UIApplication app, NSDictionary options)
        {
            RectangleF bounds = UIScreen.MainScreen.Bounds;
            MyNavigationController = new NavigationController(bounds);
            window = new UIWindow (bounds);
            window.RootViewController = MyNavigationController;
            window.MakeKeyAndVisible ();
            return true;
        }
    }

    public class NavigationController : UINavigationController
    {
        private RectangleF _bounds;
        private RectangleF _viewPort;

        public NavigationController(RectangleF bounds)
        {
            _bounds = bounds;
            NavigationBar.BarStyle = UIBarStyle.Black;
        }

        public override void ViewDidLoad()
        {
            base.ViewDidLoad();
            _viewPort = new RectangleF(_bounds.Location, new SizeF(_bounds.Width, _bounds.Height - NavigationBar.Frame.Height));
            ShowFirstView(); // Default to showing FirstViewController
        }

        public void ShowFirstView()
        {
            PushViewController(new FirstViewController(_viewPort), true);
        }

        public void ShowSecondView()
        {
            PushViewController(new SecondViewController(_viewPort), true);
        }
    }

    public class FirstViewController : UIViewController
    {
        public FirstViewController(RectangleF bounds)
        {
            // Empty view
            View = new UIView(bounds);
            View.BackgroundColor = UIColor.White;
            Title = "First View";

            // Simple button to navigate to next view
            UIButton button = UIButton.FromType(UIButtonType.RoundedRect);
            button.Frame = new RectangleF(10,10,300,30);
            button.SetTitle("Show next view", UIControlState.Normal);
            button.TouchUpInside += (sender, e) => { AppDelegate.MyNavigationController.ShowSecondView(); };
            View.AddSubview(button);
        }
    }

    public class SecondViewController : UIViewController
    {
        private NSTimer _timer;

        public SecondViewController(RectangleF bounds)
        {
            // Empty View
            View = new UIView(bounds);
            View.BackgroundColor = UIColor.Blue;
            Title = "Second View";

            // Create timer
            _timer = NSTimer.CreateRepeatingScheduledTimer(2f, delegate { Console.WriteLine("Timer Fired"); });
        }
    }
}

当我在模拟器中运行此代码时，它按预期工作，每 2 秒将“Timer Fired”写入控制台。

但是，当我附加 Apple Instruments，特别是分配工具UIApplication.Main (args, null, "AppDelegate");时，Main.cs中会引发异常

选择器从objective-c 对已被GC 处理的MonoTouch.Foundation.NSActionDispatcher (0x10AA2D50) 类型的托管对象调用

堆栈跟踪：

System.Exception: Selector invoked from objective-c on a managed object of type MonoTouch.Foundation.NSActionDispatcher (0x14FB5AC0) that has been GC'ed ---> System.Exception: No constructor found for MonoTouch.Foundation.NSActionDispatcher::.ctor(System.IntPtr)
  at System.Activator.CreateInstance (System.Type type, BindingFlags bindingAttr, System.Reflection.Binder binder, System.Object[] args, System.Globalization.CultureInfo culture, System.Object[] activationAttributes) [0x000f1] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System/Activator.cs:280
  at System.Activator.CreateInstance (System.Type type, System.Object[] args, System.Object[] activationAttributes) [0x00000] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System/Activator.cs:234
  at System.Activator.CreateInstance (System.Type type, System.Object[] args) [0x00000] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System/Activator.cs:229
  at MonoTouch.ObjCRuntime.Runtime.ConstructNSObject (IntPtr ptr, IntPtr klass) [0x0000d] in /Developer/MonoTouch/Source/monotouch/src/ObjCRuntime/Runtime.cs:231
  --- End of inner exception stack trace ---
  at MonoTouch.ObjCRuntime.Runtime.ConstructNSObject (IntPtr ptr, IntPtr klass) [0x00045] in /Developer/MonoTouch/Source/monotouch/src/ObjCRuntime/Runtime.cs:236
  at MonoTouch.ObjCRuntime.Runtime.GetNSObject (IntPtr ptr) [0x0001f] in /Developer/MonoTouch/Source/monotouch/src/ObjCRuntime/Runtime.cs:280
  at MonoTouch.ObjCRuntime.Runtime.GetNSObjectWrapped (IntPtr ptr) [0x00000] in /Developer/MonoTouch/Source/monotouch/src/ObjCRuntime/Runtime.cs:297
  at (wrapper native-to-managed) MonoTouch.ObjCRuntime.Runtime:GetNSObjectWrapped (intptr)
  at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)
  at MonoTouch.UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x0004c] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:38
  at MyNamescape.Application.Main (System.String[] args) [0x00000] in Main.cs:17

需要注意的关键事项：

应用程序在模拟器中正常运行，正常情况下（无仪器）
该问题仅在分配工具对其进行监控时发生。如果使用其他仪器（例如泄漏），则不会出现此问题。
仅当我在设置计时器之前附加分配工具时才会出现此问题。如果我在设置计时器后附加分配工具，那么它会按预期工作。
分配工具适用于我的应用程序的其他视图控制器
我找不到NSActionDispatcher与此上下文相关的太多信息，或者在 MonoTouch 中找不到更多信息
我目前无法在物理设备上进行测试。

所以我不确定这是否是分配工具的问题，或者我是否在代码中做错了什么。非常感谢有关此问题的任何建议。

编辑：我更新了代码以显示导致问题的最简单的完整应用程序用例。（我已经根据 PouPou 关于不必要使用线程的评论更新了我的计时器代码）

更新（2013 年 1 月 17 日）：我使用 iPad 和 iPhone 模拟器 5.0、5.1 和 6.0 版进行了尝试，都产生了相同的结果。

更新（2013 年 1 月 18 日）：根据 Rolf 的请求添加了本机堆栈帧。

2013-01-18 13:28:47.579 TestTimer[12196:c07]   at MonoTouch.ObjCRuntime.Runtime.ConstructNSObject (IntPtr ptr, IntPtr klass) [0x00045] in /Developer/MonoTouch/Source/monotouch/src/ObjCRuntime/Runtime.cs:236 
  at MonoTouch.ObjCRuntime.Runtime.GetNSObject (IntPtr ptr) [0x0001f] in /Developer/MonoTouch/Source/monotouch/src/ObjCRuntime/Runtime.cs:280 
  at MonoTouch.ObjCRuntime.Runtime.GetNSObjectWrapped (IntPtr ptr) [0x00000] in /Developer/MonoTouch/Source/monotouch/src/ObjCRuntime/Runtime.cs:297 
  at (wrapper native-to-managed) MonoTouch.ObjCRuntime.Runtime:GetNSObjectWrapped (intptr)
  at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)
  at MonoTouch.UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x0004c] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:38 
  at MyNamescape.Application.Main (System.String[] args) [0x00000] in Main.cs:16 
2013-01-18 13:28:47.623 TestTimer[12196:c07] 0   TestTimer                           0x00093a22 mono_handle_exception_internal_first_pass + 3058
1   TestTimer                           0x00095102 mono_handle_exception_internal + 1602
2   TestTimer                           0x00095c4f mono_handle_exception + 47
3   TestTimer                           0x000dda72 mono_x86_throw_exception + 306
4   ???                                 0x0b3e0f8f 0x0 + 188616591
at MonoTouch.ObjCRuntime.Runtime.GetNSObject (intptr) [0x0001f] in /Developer/MonoTouch/Source/monotouch/src/ObjCRuntime/Runtime.cs:280
at MonoTouch.ObjCRuntime.Runtime.GetNSObjectWrapped (intptr) [0x00000] in /Developer/MonoTouch/Source/monotouch/src/ObjCRuntime/Runtime.cs:297
at (wrapper native-to-managed) MonoTouch.ObjCRuntime.Runtime.GetNSObjectWrapped (intptr) <IL 0x00017, 0x00094>
8   TestTimer                           0x00224873 get_managed_object_for_ptr + 115
9   TestTimer                           0x00229700 monotouch_trampoline + 448
10  Foundation                          0x019b9b90 __NSFireTimer + 97
11  CoreFoundation                      0x01315376 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 22
12  CoreFoundation                      0x01314e06 __CFRunLoopDoTimer + 534
13  CoreFoundation                      0x012fca82 __CFRunLoopRun + 1810
14  CoreFoundation                      0x012fbf44 CFRunLoopRunSpecific + 276
15  CoreFoundation                      0x012fbe1b CFRunLoopRunInMode + 123
16  GraphicsServices                    0x04b807e3 GSEventRunModal + 88
17  GraphicsServices                    0x04b80668 GSEventRun + 104
18  UIKit                               0x0273965c UIApplicationMain + 1211
at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication.UIApplicationMain (int,string[],intptr,intptr) <IL 0x00056, 0x001f5>
at MonoTouch.UIKit.UIApplication.Main (string[],string,string) [0x0004c] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:38
at MyNamescape.Application.Main (string[]) [0x00000] in Main.cs:16
at (wrapper runtime-invoke) <Module>.runtime_invoke_void_object (object,intptr,intptr,intptr) <IL 0x00049, 0x0014e>
23  TestTimer                           0x00010252 mono_jit_runtime_invoke + 722
24  TestTimer                           0x0017478e mono_runtime_invoke + 126
25  TestTimer                           0x00178be4 mono_runtime_exec_main + 420
26  TestTimer                           0x00178f55 mono_runtime_run_main + 725
27  TestTimer                           0x0006ba65 mono_jit_exec + 149
28  TestTimer                           0x0021f65d main + 2013
29  TestTimer                           0x00003125 start + 53

score 2 · Accepted Answer

我（最终）发现这是 MonoTouch 中的一个错误（仪器拦截了保留/释放方法，这使 MonoTouch 感到困惑）。该错误已修复，并将包含在下一个稳定版本（6.0.9）中。

c# - 连接仪器时 NSActionDispatcher 被垃圾收集

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