在 Xamarin.Android 上未选中“使用共享运行时”的 Mvvmcross 绑定失败答案

【问题标题】：Mvvmcross binding failure with "Use Shared Runtime" unchecked on Xamarin.Android在 Xamarin.Android 上未选中“使用共享运行时”的 Mvvmcross 绑定失败
【发布时间】：2014-11-09 16:16:56
【问题描述】：

我有一个应用程序在 Debug 构建中运行良好，并且主要在 Release 中运行，但我在这个问题的底部得到了堆栈跟踪。似乎失败的绑定是按钮的启用属性。我认为这是因为如果我把它拿出来，其他绑定就可以了。下面还有简化的视图模型代码和 ui axml。我已将发布版本和调试版本之间的相关差异本地化为“使用共享运行时”构建设置。选择此选项后，它可以工作。没有它就会失败。不幸的是，如果选择了此选项，我将无法打包构建以进行分发。有谁知道这里发生了什么？

VisualStudio 2012 Xamarin 3.5.58.0

导致问题的按钮的ui axml sn-p

<Button
   android:padding="2dip"
   android:layout_weight="1"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   local:MvxBind="Click SendConfigCommand; Enabled ButtonEnabledSendConfig; Text ButtonLabelSendConfig, Mode=OneTime; LongClick HelpCommand, CommandParameter=HelpContinueDevice" />

ViewModel sn-p 用于按钮使用的属性（为调试buoi而简化）

    public string ButtonLabelSendConfig
    {
        get{return "Next";}
    }

    public bool ButtonEnabledSendConfig
    {
        get { return false; }
    }

    public ICommand SendConfigCommand
    {
        get
        {
            return m_SendConfigCommand ?? (m_SendConfigCommand = new MvxCommand(() =>
            {
               //Intentionally left empty
            }));
        }
    }
    private MvxCommand m_SendConfigCommand;

来自视图模型基类

    public MvxCommand<string> HelpCommand
    {
        get { return this._HelpCommand ?? (this._HelpCommand = new MvxCommand<string>(key =>
        {
            var prompter = Mvx.Resolve<IUserInteraction>();
            prompter.Alert(Localised.ResourceManager.GetString(key), null, Localised.Help, Localised.OkayButton);
        })); }
    }
    private MvxCommand<string> _HelpCommand;

堆栈跟踪

MvxBind:Error:653.39 Exception thrown during the view binding NullReferenceException: Object reference not set to an instance of an object
09-16 13:21:45.456 I/MvxBind (29040): 653.39 Exception thrown during the view binding NullReferenceException: Object reference not set to an instance of an object

      at Cirrious.CrossCore.ReflectionExtensions+<>c__DisplayClass7.<GetProperties>b__4 (System.Reflection.PropertyInfo p) [0x00000] in <filename unknown>:0 
  at System.Linq.Enumerable+<CreateWhereIterator>c__Iterator1F`1[System.Reflection.PropertyInfo].MoveNext () [0x00000] in <filename unknown>:0 
  at System.Linq.Enumerable+<CreateWhereIterator>c__Iterator1E`1[System.Reflection.PropertyInfo].MoveNext () [0x00000] in <filename unknown>:0 
  at System.Linq.Enumerable+<CreateWhereIterator>c__Iterator1E`1[System.Reflection.PropertyInfo].MoveNext () [0x00000] in <filename unknown>:0 
  at System.Linq.Enumerable.First[PropertyInfo] (IEnumerable`1 source, System.Func`2 predicate, Fallback fallback) [0x00000] in <filename unknown>:0 
  at System.Linq.Enumerable.FirstOrDefault[PropertyInfo] (IEnumerable`1 source, System.Func`2 predicate) [0x00000] in <filename unknown>:0 
  at Cirrious.CrossCore.ReflectionExtensions.GetProperty (System.Type type, System.String name) [0x00000] in <filename unknown>:0 
  at Cirrious.M
09-16 13:21:45.456 I/MvxBind (29040):     at Cirrious.CrossCore.ReflectionExtensions+<>c__DisplayClass7.<GetProperties>b__4 (System.Reflection.PropertyInfo p) [0x00000] in <filename unknown>:0 
[0:] MvxBind:Error:653.39 Exception thrown during the view binding NullReferenceException: Object reference not set to an instance of an object
      at Cirrious.CrossCore.ReflectionExtensions+<>c__DisplayClass7.<GetProperties>b__4 (System.Reflection.PropertyInfo p) [0x00000] in <filename unknown>:0 
  at System.Linq.Enumerable+<CreateWhereIterator>c__Iterator1F`1[System.Reflection.PropertyInfo].MoveNext () [0x00000] in <filename unknown>:0 
  at System.Linq.Enumerable+<CreateWhereIterator>c__Iterator1E`1[System.Reflection.PropertyInfo].MoveNext () [0x00000] in <filename unknown>:0 
  at System.Linq.Enumerable+<CreateWhereIterator>c__Iterator1E`1[System.Reflection.PropertyInfo].MoveNext () [0x00000] in <filename unknown>:0 
  at System.Linq.Enumerable.First[PropertyInfo] (IEnumerable`1 source, System.Func`2 predicate, Fallback fallback) [0x00000] in <filename unknown>:0 
  at System.Linq.Enumerable.FirstOrDefault[PropertyInfo] (IEnumerable`1 source, System.Func`2 predicate) [0x00000] in <filename unknown>:0 
  at Cirrious.CrossCore.ReflectionExtensions.GetProperty (System.Type type, System.String name) [0x00000] in <filename unknown>:0 
  at Cirrious.MvvmCross.Binding.Bindings.Target.Construction.MvxTargetBindingFactoryRegistry.TryCreateReflectionBasedBinding (System.Object target, System.String targetName, IMvxTargetBinding& binding) [0x00000] in <filename unknown>:0 
  at Cirrious.MvvmCross.Binding.Bindings.Target.Construction.MvxTargetBindingFactoryRegistry.CreateBinding (System.Object target, System.String targetName) [0x00000] in <filename unknown>:0 
  at Cirrious.MvvmCross.Binding.Bindings.MvxFullBinding.CreateTargetBinding (System.Object target) [0x00000] in <filename unknown>:0 
  at Cirrious.MvvmCross.Binding.Bindings.MvxFullBinding..ctor (Cirrious.MvvmCross.Binding.MvxBindingRequest bindingRequest) [0x00000] in <filename unknown>:0 
  at Cirrious.MvvmCross.Binding.Binders.MvxFromTextBinder.BindSingle (Cirrious.MvvmCross.Binding.MvxBindingRequest bindingRequest) [0x00000] in <filename unknown>:0 
  at Cirrious.MvvmCross.Binding.Binders.MvxFromTextBinder+<>c__DisplayClass1.<Bind>b__0 (Cirrious.MvvmCross.Binding.Bindings.MvxBindingDescription description) [0x00000] in <filename unknown>:0 
  at System.Linq.Enumerable+<CreateSelectIterator>c__Iterator10`2[Cirrious.MvvmCross.Binding.Bindings.MvxBindingDescription,Cirrious.MvvmCross.Binding.Bindings.IMvxUpdateableBinding].MoveNext () [0x00000] in <filename unknown>:0 
  at System.Collections.Generic.List`1[Cirrious.MvvmCross.Binding.Bindings.IMvxUpdateableBinding].AddEnumerable (IEnumerable`1 enumerable) [0x00000] in <filename unknown>:0 
  at System.Collections.Generic.List`1[Cirrious.MvvmCross.Binding.Bindings.IMvxUpdateableBinding].AddRange (IEnumerable`1 collection) [0x00000] in <filename unknown>:0 
  at Cirrious.MvvmCross.Binding.Droid.Binders.MvxAndroidViewBinder.ApplyBindingsFromAttribute (Android.Views.View view, Android.Content.Res.TypedArray typedArray, Int32 attributeId) [0x00000] in <filename unknown>:0 
vvmCross.Binding.Bindings.Target.Construction.MvxTargetBindingFactoryRegistry.TryCreateReflectionBasedBinding (System.Object target, System.String targetName, IMvxTargetBinding& binding) [0x00000] in <filename unknown>:0 
  at Cirrious.MvvmCross.Binding.Bindings.Target.Construction.MvxTargetBindingFactoryRegistry.CreateBinding (System.Object target, System.String targetName) [0x00000] in <filename unknown>:0 
  at Cirrious.MvvmCross.Binding.Bindings.MvxFullBinding.CreateTargetBinding (System.Object target) [0x00000] in <filename unknown>:0 
  at Cirrious.MvvmCross.Binding.Bindings.MvxFullBinding..ctor (Cirrious.MvvmCross.Binding.MvxBindingRequest bindingRequest) [0x00000] in <filename unknown>:0 
  at Cirrious.MvvmCross.Binding.Binders.MvxFromTextBinder.BindSingle (Cirrious.MvvmCross.Binding.MvxBindingRequest bindingRequest) [0x00000] in <filename unknown>:0 
  at Cirrious.MvvmCross.Binding.Binders.MvxFromTextBinder+<>c__DisplayClass1.<Bind>b__0 (Cirrious.MvvmCross.Binding.Bindings.MvxBindingDescription descr
09-16 13:21:45.456 I/MvxBind (29040):   at System.Linq.Enumerable+<CreateWhereIterator>c__Iterator1F`1[System.Reflection.PropertyInfo].MoveNext () [0x00000] in <filename unknown>:0 
iption) [0x00000] in <filename unknown>:0 
  at System.Linq.Enumerable+<CreateSelectIterator>c__Iterator10`2[Cirrious.MvvmCross.Binding.Bindings.MvxBindingDescription,Cirrious.MvvmCross.Binding.Bindings.IMvxUpdateableBinding].MoveNext () [0x00000] in <filename unknown>:0 
  at System.Collections.Generic.List`1[Cirrious.MvvmCross.Binding.Bindings.IMvxUpdateableBinding].AddEnumerable (IEnumerable`1 enumerable) [0x00000] in <filename unknown>:0 
  at System.Collections.Generic.List`1[Cirrious.MvvmCross.Binding.Bindings.IMvxUpdateableBinding].AddRange (IEnumerable`1 collection) [0x00000] in <filename unknown>:0 
  at Cirrious.MvvmCross.Binding.Droid.Binders.MvxAndroidViewBinder.ApplyBindingsFromAttribute (Android.Views.View view, Android.Content.Res.TypedArray typedArray, Int32 attributeId) [0x00000] in <filename unknown>:0

【问题讨论】：

标签： xamarin.android mvvmcross

【解决方案1】：

这很可能是由于链接器造成的。 MvvmCross 使用反射来执行数据绑定。由于对 Enabled 属性的唯一引用是在布局文件中，因此链接器不会将其包含在最终程序集中。

MvvmCross 在您的 Android 项目中添加一个名为 LinkerPleaseInclude.cs 的文件。您需要在其中添加对该属性的引用以确保它被链接。

类似这样的：

    public void Include(Button button)
    {
        button.Click += (s,e) => button.Text = button.Text + "";
        button.Enabled = !button.Enabled;
    }

另请参阅：mvvmcross binding on switch fails on release

【讨论】：

今天早上我在做其他事情时正在考虑这个问题。我怀疑你是对的。当我有机会时会检查并标记您的答案。我想知道 MVVMCross 是否有一种方法可以检测到这一点并记录错误消息，而不仅仅是一个模糊的堆栈跟踪。
嗯...这似乎是一个链接问题。我可以关闭链接，它适用于发布版本（大小是 6 倍！）。我尝试将 button.Enabled 和 button.LongClick 添加到“LinkerPleaseInclude”类，但这似乎没有帮助，我得到了相同的堆栈跟踪。