向后导航不会释放内存

Question

在我的应用程序上,使用Xamarin Profiler我注意到每当我将VC推送到堆栈并导航回来时,内存分配就不是免费的.如果我再次推送相同的视图,它会增加更多内存.

我创建了一个示例项目来测试,我发现这是同样的事情.

示例项目:

我有两个视图控制器,VC1和VC2.VC1是根视图控制器.

每当我从VC1推送VC2时,就会分配内存,但是当我向后导航时,内存不是空闲的.如果我再次继续推动VC2,它会增加更多内存.在VC2中,我通过设计师添加了3个标签.

在AppDelegate中:

namespace TestSample
{
    [Register("AppDelegate")]
    public class AppDelegate : UIApplicationDelegate
    {
        public override UIWindow Window
        {
            get;
            set;
        }

        public override bool FinishedLaunching(UIApplication application, NSDictionary launchOptions)
        {
            Window = new UIWindow(UIScreen.MainScreen.Bounds);
            var nav = new UINavigationController(new MyViewController());
            Window.RootViewController = nav;
            Window.MakeKeyAndVisible();

            return true;
        }
    }
}

VC1:

namespace TestSample
{
    public partial class MyViewController : UIViewController
    {
        public MyViewController() : base("MyViewController", null)
        {
        }

        public override void ViewDidLoad()
        {
            base.ViewDidLoad();
            // Perform any additional setup after loading the view, typically from a nib.
        }
        public override void ViewWillAppear(bool animated)
        {
            base.ViewWillAppear(animated);

            btn1.TouchUpInside += Btn1_TouchUpInside;
        }

        void Btn1_TouchUpInside(object sender, EventArgs e)
        {
            NavigationController.PushViewController(new MyViewController2(), true);
        }

        public override void ViewDidDisappear(bool animated)
        {
            base.ViewDidDisappear(animated);
            btn1.TouchUpInside -= Btn1_TouchUpInside;
        }

        public override void DidReceiveMemoryWarning()
        {
            base.DidReceiveMemoryWarning();
            // Release any cached data, images, etc that aren't in use.
        }
    }
}

VC2:

namespace TestSample
{
    public partial class MyViewController2 : UIViewController
    {
        public MyViewController2() : base("MyViewController2", null)
        {
        }

        public override void ViewDidLoad()
        {
            base.ViewDidLoad();
            // Perform any additional setup after loading the view, typically from a nib.
        }

        public override void DidReceiveMemoryWarning()
        {
            base.DidReceiveMemoryWarning();
            // Release any cached data, images, etc that aren't in use.
        }

        public override void ViewDidDisappear(bool animated)
        {
            base.ViewDidDisappear(animated);
            /*foreach (UIView view in View.Subviews) {
                view.RemoveFromSuperview();
            }*/

            label1.RemoveFromSuperview();
            label2.RemoveFromSuperview();
            label3.RemoveFromSuperview();

            label1.Dispose();
            label2.Dispose();
            label3.Dispose();
        }
    }
}

Answer 1

Xamarin.iOS中的垃圾收集根本没有破坏.这是一个普遍的误解(在任何系统上!)有一个GC意味着人们不必担心要小心内存消耗和(强)引用.

X.iOS位于参考计数世界的顶部,这需要进行某些测量.所有这些都记录在案; 是的,很难理解所有的细微差别.

那说:我尝试了你的例子,VC2按预期收集(Finalizer并被Dispose()调用).此外,Profiler(1.0.2-2)也没有显示任何泄漏.

我创建了两个基于XIB的控制器,并为第一个添加了一个按钮,为第二个添加了一个标签.您不必删除或处置任何标签,也不必取消订阅您案例中第一个VC中的click事件.

如果您的项目行为不同,则会在某处保留对VC2的引用.也许你可以提供完整的项目,然后我可以看看它.