Question

我添加了一个没有运气的linkerPleaseInclude。

下面是我目前实施的一些代码，我没看到我做错了什么。

绑定时，以下行会引发异常。

        this.CreateBinding(MyTextView).For(v => v.Text).To<MyViewModel>(vm => vm.QuestionText).Apply();

视图中的财产声明

          MyTextView = new UITextView(new CGRect(0, 0, myWidth, 105))
        {
            TranslatesAutoresizingMaskIntoConstraints = false,
            TextColor = UIColor.Black,
            Font = UIFont.FromName("Avenir-Heavy", 15f),
            TextAlignment = UITextAlignment.Left,
            BackgroundColor = UIColor.Clear,
            //Alpha = .3f,
            ScrollEnabled = true,
            Editable = false,
            IndicatorStyle = UIScrollViewIndicatorStyle.White
        };

继承ViewModel中的财产声明

string _questionText;
public string QuestionText
{
  get { return _questionText; }
  set
  {
    _questionText = value;
    RaisePropertyChanged(() => QuestionText);
  }
 }

这是例外：

未处理的异常：System.ArgumentNullException：缺少源 MvxWeakEventSubscription中的事件信息参数名称：sourceEventInfo 在 MvvmCross.Platform.WeakSubscription.MvxWeakEventSubscription 2[TSource,TEventArgs]..ctor (UIKit.NSTextStorage source, System.Reflection.EventInfo sourceEventInfo, System.EventHandler 1 [TEventArgs] targetEventHandler） [0x00017]在＆lt; 6adc0d5857264558a9d45778a78ae02a＆gt;中：0 at MvvmCross.Platform.WeakSubscription.MvxWeakEventSubscription 2[TSource,TEventArgs]..ctor (UIKit.NSTextStorage source, System.String sourceEventName, System.EventHandler 1 [TEventArgs] targetEventHandler）[0x00012] in ＆lt; 6adc0d5857264558a9d45778a78ae02a＆gt;：0 at MvvmCross.Platform.WeakSubscription.MvxWeakSubscriptionExtensionMethods.WeakSubscribe [TSource，TEventArgs] （TSource源代码，System.String eventName， System.EventHandler 1[TEventArgs] eventHandler) [0x00000] in <6adc0d5857264558a9d45778a78ae02a>:0 at MvvmCross.Binding.iOS.Target.MvxUITextViewTextTargetBinding.SubscribeToEvents () [0x00053] in <614c9ef828c14ba687a40ec2656f480f>:0 at MvvmCross.Binding.Bindings.MvxFullBinding.CreateTargetBinding (System.Object target) [0x00057] in <866b1e46764b48aab0d408952a6f006f>:0 at MvvmCross.Binding.Bindings.MvxFullBinding..ctor (MvvmCross.Binding.MvxBindingRequest bindingRequest) [0x0002f] in <866b1e46764b48aab0d408952a6f006f>:0 at MvvmCross.Binding.Binders.MvxFromTextBinder.BindSingle (MvvmCross.Binding.MvxBindingRequest bindingRequest) [0x00000] in <866b1e46764b48aab0d408952a6f006f>:0 at MvvmCross.Binding.Binders.MvxFromTextBinder+<>c__DisplayClass2_0.<Bind>b__0 (MvvmCross.Binding.Bindings.MvxBindingDescription description) [0x00018] in <866b1e46764b48aab0d408952a6f006f>:0 at System.Linq.Enumerable+SelectArrayIterator 2 [TSource，TResult] .MoveNext （）[0x0003a]在＆lt; 8bc31b0df50a4d32b3f1d5af764165ad＆gt;：0 at MvvmCross.Binding.BindingContext.MvxBindingContextOwnerExtensions.AddBindings （MvvmCross.Binding.BindingContext.IMvxBindingContextOwner视图， System.Object target，System.Collections.Generic.IEnumerable 1[T] bindings, System.Object clearKey) [0x0001d] in <866b1e46764b48aab0d408952a6f006f>:0 at MvvmCross.Binding.BindingContext.MvxBindingContextOwnerExtensions.AddBindings (MvvmCross.Binding.BindingContext.IMvxBindingContextOwner view, System.Object target, System.Collections.Generic.IEnumerable 1 [T] bindingDescriptions，System.Object clearKey）[0x00018] in ＆lt; 866b1e46764b48aab0d408952a6f006f＆gt;：0 at MvvmCross.Binding.BindingContext.MvxBindingContextOwnerExtensions.AddBinding （MvvmCross.Binding.BindingContext.IMvxBindingContextOwner视图， System.Object目标，MvvmCross.Binding.Bindings.MvxBindingDescription bindingDescription，System.Object clearKey）[0x0000b] in ＆lt; 866b1e46764b48aab0d408952a6f006f＆gt;：0 at MvvmCross.Binding.BindingContext.MvxBaseFluentBindingDescription`1 [t目标]。适用（）[0x0001f] in＆lt; 866b1e46764b48aab0d408952a6f006f＆gt;：0 at BALAHA.iOS.Views.RecordingView.SetupBindings（）[0x00418] in /Users/BALAHA_mbp/Projects/BALAHA/BALAHA/iOS/Views/RecordingView.cs:799 在BALAHA.iOS.Views.RecordingView.ViewDidLoad（）[0x0002f] in /Users/BALAHA_mbp/Projects/BALAHA/BALAHA/iOS/Views/RecordingView.cs:114 at（包装器托管到原生）UIKit.UIApplication：UIApplicationMain UIKit.UIApplication.Main上的（int，string []，intptr，intptr）（System.String [] args，System.IntPtr principal，System.IntPtr 代表）[0x00005] in /Users/builder/data/lanes/5665/f70a1348/source/xamarin-macios/src/UIKit/UIApplication.cs:79 在UIKit.UIApplication.Main（System.String [] args，System.String principalClassName，System.String delegateClassName）[0x00038] in /Users/builder/data/lanes/5665/f70a1348/source/xamarin-macios/src/UIKit/UIApplication.cs:63 在BALAHA.iOS.Application.Main（System.String [] args）[0x00001]中 /Users/BALAHA_mbp/Projects/BALAHA/BALAHA/iOS/Main.cs:17 2018-01-12 18：23：28.985 BALAHA.iOS [888：372317]未处理的管理异常：在MvxWeakEventSubscription中缺少源事件信息

Answer 1

将此添加到LinkerPleaseInclude解决了我的问题：

public void Include(UITextView textView)
{
    textView.Text = textView.Text + "";            
    textView.Changed += (sender, args) => { textView.Text = ""; };            
    textView.TextStorage.DidProcessEditing += (sender, e) => textView.Text = "";
}

Answer 2

读取错误消息似乎问题是由链接器引起的。您似乎没有在Xamarin.iOS项目中包含LinkerPleaseInclude.cs文件。请参阅其他类似问题here，here或here。

在链接过程中，Xamarin.iOS会从二进制文件中删除所有未使用的内容。这意味着从未访问过的字段和属性对于反射是不可见的。 LinkerPleaseInclude.cs的示例可以是found here。它包含最常用的控件及其属性，但您可以添加只会触及链接期间不想丢失的属性的方法。

Answer 3

由于实施此解决方案的正确方法对我不起作用，我必须执行以下操作：

在视图中：

string _viewModelText;
    public string ViewModelText
    {
        get { return _viewModelText; }
        set
        {
            _viewModelText = value;

            if (_viewModelText != null)
            {
                MyTextView.Text = _viewModelText;
            }
        }
    }

    this.CreateBinding(this).For(v => v.ViewModelText).To<MyViewModel>(vm => vm.QuestionText).OneWay().Apply();

这解决了这个问题，虽然它以一种迂回的方式完成了工作。

更新

虽然上述方法有效但原始异常的原因是ViewModel属性的使用不当。

ViewModel的属性应按如下方式实现：

    string _questionText;
    public string QuestionText
    {
        get { return _questionText; }
        set { SetProperty(ref _questionText, value); }
    }

然后，您可以将Textview的文本属性绑定为：

    this.CreateBinding(MyTextView).For(v => v.Text).To<MyViewModel>(vm => vm.QuestionText).Apply();

绑定到ViewModel

3 个答案: