列表的 DataContractSerializer 失败<bool>在 Android 上使用 Unity3d 的 IL2CPP 编译时出现“未生成提前 (AOT) 代码”错误</bool>

Question

我已将序列化更改为 DataContracts，但现在我遇到了特定 class 的问题。 它在我的 Mac 上运行良好，但在使用 IL2CPP 构建时在我的 android 设备上运行良好。 线程在 writeObject function 处停止。 我与错误相关的三个类：

[DataContract]
[KnownType(typeof(TaskIdentifier))]
[KnownType(typeof(TraceableTaskItem))]
[KnownType(typeof(List<TraceableTaskItem>))]
public class TraceableTaskContainer
{
    [DataMember]
    protected TaskIdentifier _taskIdent;

    [DataMember]
    protected List<TraceableTaskItem> _lNotAccomplishedTaskItems = new List<TraceableTaskItem>();

//.....
}

[DataContract]
[KnownType(typeof(DateTime))]
[KnownType(typeof(ItemReviewStage))]
public class TraceableTaskItem : GenericTaskItem, IEquatable<TraceableTaskItem>, IComparable<TraceableTaskItem>
{
    [DataMember]
    public string sDisplayTextInTraceableTaskReport;

    [DataMember]
    protected DateTime NextReviewDate;

    [DataMember] //ItemReviewStage is a enum
    protected ItemReviewStage reviewStage = ItemReviewStage.NewTask;

   
    public TraceableTaskItem() //important to deserialize old classes, do not remove it
    {

    }
//....
}

[DataContract]
//[KnownType(typeof(List<bool>))]
abstract public class GenericTaskItem
{
    [DataMember]
    public string sItemID = "";

    //[DataMember]
    protected List<bool> lTimesAnsweredCorrectly = new List<bool>();

    protected List<List<string>> llWrongAnswers = new List<List<string>>();

//...
}

该代码适用于上面的注释行。 但是，只要我在 lTimesAnsweredCorrely 上取消注释 DataMember 并且无论是否取消注释等效的 KnownType 行（我都测试过），代码就会停止在我的移动设备上运行。 知道如何解决这个问题吗？

例外：

"System.Reflection.TargetInvocationException: 
Exception has been thrown by the target of an invocation. 
---> System.ExecutionEngineException: Attempting to call method \'System.Runtime.Serialization.XmlObjectSerializerWriteContext::
IncrementCollectionCountGeneric<System.Boolean>\' 
for which no ahead of time (AOT) code was generated.\n  at 
System.Reflection.MonoMethod.Invoke (System.Object obj, 
System.Reflection.BindingFlags invokeAttr, 
System.Reflection.Binder binder, System.Object[] parameters, 
System.Globalization.CultureInfo culture) [0x00000] 
in <00000000000000000000000000000000>:0 \n  at 
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] 
in <00000000000000000000000000000000>:0 \n  at System.Runtime.Serialization.XmlFormatWriterInterpreter.WriteCollection (System.Runtime.Serialization.CollectionDataContract collectionContract) [0x00000] 
in <00000000000000000000000000000000>:0 \n  at 
System.Runtime.Serialization.XmlFormatWriterInt… string



 StackTrace: "  at System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <00000000000000000000000000000000>:0 \n  at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] in <00000000000000000000000000000000>:0 \n  at System.Runtime.Serialization.XmlFormatWriterInterpreter.WriteCollection (System.Runtime.Serialization.CollectionDataContract collectionContract) [0x00000] in <00000000000000000000000000000000>:0 \n  at System.Runtime.Serialization.XmlFormatWriterInterpreter.WriteCollectionToXml (System.Runtime.Serialization.XmlWriterDelegator xmlWriter, System.Object obj, System.Runtime.Serialization.XmlObjectSerializerWriteContext context, System.Runtime.Serialization.CollectionDataContract collectionContract) [0x00000] in <00000000000000000000000000000000>:0 \n  at System.Runtime.Serialization.XmlForma… string

Source: "mscorlib" string

inner exception: 
 InnerException "System.ExecutionEngineException: Attempting to call method \'System.Runtime.Serialization.XmlObjectSerializerWriteContext::
IncrementCollectionCountGeneric<System.Boolean>\' for which no ahead of time (AOT) code was generated.\n  at System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <00000000000000000000000000000000>:0 \n  at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] in <00000000000000000000000000000000>:0 \n  at System.Runtime.Serialization.XmlFormatWriterInterpreter.WriteCollection (System.Runtime.Serialization.CollectionDataContract collectionContract) [0x00000] in <00000000000000000000000000000000>:0 \n  at System.Runtime.Serialization.XmlFormatWriterInterpreter.WriteCollectionToXml (System.Runtime.Serialization.XmlWriterDelegator xmlWriter, System.Object obj, System.Ru… System.Exception

更新

问题似乎只出在bool和int上，字符串列表按预期工作。

Answer 1

根据你的说法

问题似乎只出在bool和int上，字符串列表按预期工作。

看来，在 Android 上，框架的提前编译没有为 .NET 内部方法XmlObjectSerializerWriteContext.IncrementCollectionCountGeneric<T>(XmlWriterDelegator xmlWriter, ICollection<T> collection) T必要的代码类型如bool或int ，但它正在为引用类型生成必要的代码。 ^[1]

这可能是您在 Android 上使用的运行时或框架中的错误。 您可能想向供应商报告问题。

作为一种解决方法，由于诸如List<string>之类的 collections 确实序列化成功，您可以为您的List<bool>和List<int>创建代理 collections，它们在序列化程序看来是 Z0B9ABFE67CC31FCF1ZECD022EB19A52，并执行必要的 string-to1， -bool（或字符串到整数）内部转换。

首先，定义以下类：

[CollectionDataContract(Name = "ArrayOfboolean", ItemName = "boolean", Namespace = "http://schemas.microsoft.com/2003/10/Serialization/Arrays")]
public class XmlBoolList : ConvertingList<bool, List<bool>, string>
{
    public XmlBoolList(List<bool> list) : base(() => list, b => XmlConvert.ToString(b), s => XmlConvert.ToBoolean(s)) { }
    public XmlBoolList() : this(new List<bool>()) { }
}

[CollectionDataContract(Name = "ArrayOfint", ItemName = "int", Namespace = "http://schemas.microsoft.com/2003/10/Serialization/Arrays")]
public class XmlIntList : ConvertingList<int, List<int>, string>
{
    public XmlIntList(List<int> list) : base(() => list, i => XmlConvert.ToString(i), s => XmlConvert.ToInt32(s)) { }
    public XmlIntList() : this(new List<int>()) { }
}

public class ConvertingList<TIn, TList, TOut> : IList<TOut> where TList : IList<TIn>
{
    readonly Func<TList> getList;
    readonly Func<TIn, TOut> toOuter;
    readonly Func<TOut, TIn> toInner;

    public ConvertingList(Func<TList> getList, Func<TIn, TOut> toOuter, Func<TOut, TIn> toInner)
    {
        if (getList == null || toOuter == null || toInner == null)
            throw new ArgumentNullException();
        this.getList = getList;
        this.toOuter = toOuter;
        this.toInner = toInner;
    }

    public TList List => getList();
    TIn ToInner(TOut outer)=> toInner(outer);
    TOut ToOuter(TIn inner)=> toOuter(inner);

    #region IList<TOut> Members

    public int IndexOf(TOut item) => List.IndexOf(toInner(item));
    public void Insert(int index, TOut item) => List.Insert(index, ToInner(item));
    public void RemoveAt(int index) => List.RemoveAt(index);
    public TOut this[int index] { get => ToOuter(List[index]); set => List[index] = ToInner(value); }

    #endregion

    #region ICollection<TOut> Members

    public void Add(TOut item) => List.Add(ToInner(item));
    public void Clear() => List.Clear();
    public bool Contains(TOut item) => List.Contains(ToInner(item));
    public void CopyTo(TOut[] array, int arrayIndex)
    {
        foreach (var item in this)
            array[arrayIndex++] = item;
    }
    public int Count => List.Count;
    public bool IsReadOnly => List.IsReadOnly;
    public bool Remove(TOut item) => List.Remove(ToInner(item));

    #endregion

    #region IEnumerable<TOut> Members

    public IEnumerator<TOut> GetEnumerator()
    {
        foreach (var item in List)
            yield return ToOuter(item);
    }

    #endregion

    #region IEnumerable Members

    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();

    #endregion
}

现在修改您的类型GenericTaskItem包含一个List<bool>通过添加私有代理XmlBoolList属性用于序列化目的：

abstract public class GenericTaskItem
{
    [DataMember]
    public string sItemID = "";

    [IgnoreDataMember]
    protected List<bool> lTimesAnsweredCorrectly = new List<bool>();
    
    [DataMember(Name = "lTimesAnsweredCorrectly")]
    XmlBoolList lTimesAnsweredCorrectlySurrogate { get => lTimesAnsweredCorrectly == null ? null : new XmlBoolList(lTimesAnsweredCorrectly); set => lTimesAnsweredCorrectly = value?.List; }

    //...
}

现在，序列化程序会将XmlBoolList序列化为引用类型数组，具体来说。

笔记：

• XmlConvert class 可用于将 .NET 原语与 XML 值转换。

• XmlBoolList和XmlIntList被设计为分别具有与List<bool>和List<int>相同的集合数据协定。

• [KnownType(typeof(T))]属性仅在序列化多态 object 图时需要，其中被序列化的实际类型与声明的类型不同，而List<bool>和XmlBoolList属性中的情况并非如此。 有关详细信息，请参阅数据协定已知类型。

• 您可能会调查使用数据合约代理来替换值类型（例如List<bool> ）的 collections 全局而不是基于每个属性。

演示小提琴在这里。

---

^[1]这令人惊讶——但并不完全令人惊讶。 .NET 运行时实现对 generics 的引用类型与 generics 的值类型非常不同的支持； 有关详细信息，请参阅运行时（C# 编程指南）中的 Generics 。