Xamarin Android - Linker和ServiceStack.Text

Question

我很难让一个应用程序与全链接工作。这是我的设置(我的程序集名称更改了)：

• 用于Android 4.4.54的Mono
• 安卓应用程序(MyApp)
• 一个平台无关的库(MyLib)

我试图使用ServiceStack.Text从JSON文本中反序列化类型(Person)。只有链接SDK程序集时，它才能正常工作。

我在MyLib中使用的不是链接器包含属性，而是在MyApp中使用LinkDescription XML文件。看起来是这样的：

<?xml version="1.0" encoding="utf-8" ?>
<linker>
  <assembly fullname="MyLib">
    <type fullname="MyLib.Person" preserve="fields">
      <method name=".ctor" />
    </type>
  </assembly>
</linker>

这是我的logcat输出：

E/MyApp(14494): InitialiseUser(): System.TypeInitializationException: An exception was thrown by the type initializer for ServiceStack.Text.Json.JsonReader`1 ---> System.ArgumentNullException: Argument cannot be null.
E/MyApp(14494): Parameter name: method
E/MyApp(14494):   at System.Delegate.CreateDelegate (System.Type type, System.Object firstArgument, System.Reflection.MethodInfo method, Boolean throwOnBindFailure, Boolean allowClosed) [0x00000] in <filename unknown>:0 
E/MyApp(14494):   at System.Delegate.CreateDelegate (System.Type type, System.Reflection.MethodInfo method, Boolean throwOnBindFailure) [0x00000] in <filename unknown>:0 
E/MyApp(14494):   at ServiceStack.Text.PlatformExtensions.MakeDelegate (System.Reflection.MethodInfo mi, System.Type delegateType, Boolean throwOnBindFailure) [0x00000] in <filename unknown>:0 
E/MyApp(14494):   at ServiceStack.Text.Json.JsonReader.GetParseFn (System.Type type) [0x00000] in <filename unknown>:0 
E/MyApp(14494):   at ServiceStack.Text.Json.JsonTypeSerializer.GetParseFn (System.Type type) [0x00000] in <filename unknown>:0 
E/MyApp(14494):   at ServiceStack.Text.Common.TypeAccessor.Create (ITypeSerializer serializer, ServiceStack.Text.TypeConfig typeConfig, System.Reflection.PropertyInfo propertyInfo) [0x00000] in <filename unknown>:0 
E/MyApp(14494):   at ServiceStack.Text.Common.DeserializeTypeRef.GetTypeAccessorMap (ServiceStack.Text.TypeConfig typeConfig, ITypeSerializer serializer) [0x00000] in <filename unknown>:0 
E/MyApp(14494):   at ServiceStack.Text.Common.DeserializeType`1[ServiceStack.Text.Json.JsonTypeSerializer].GetParseMethod (ServiceStack.Text.TypeConfig typeConfig) [0x00000] in <filename unknown>:0 
E/MyApp(14494):   at ServiceStack.Text.Common.JsReader`1[ServiceStack.Text.Json.JsonTypeSerializer].GetCoreParseFn[Person] () [0x00000] in <filename unknown>:0 
E/MyApp(14494):   at ServiceStack.Text.Common.JsReader`1[ServiceStack.Text.Json.JsonTypeSerializer].GetParseFn[Person] () [0x00000] in <filename unknown>:0 
E/MyApp(14494):   at ServiceStack.Text.Json.JsonReader`1[MyLib.Person]..cctor () [0x00000] in <filename unknown>:0 
E/MyApp(14494):   --- End of inner exception stack trace ---
E/MyApp(14494):   at ServiceStack.Text.JsonSerializer.DeserializeFromString[Person] (System.String value) [0x00000] in <filename unknown>:0 
E/MyApp(14494):   at MyLib.Person.FromJson (System.String json, Boolean throwOnNullOrEmpty) [0x00000] in <filename unknown>:0 
E/MyApp(14494):   at MyApp.MainActivity.InitialiseUser () [0x00000] in <filename unknown>:0 

在此之后，我的Person实例为空。

从输出结果看，无法找到Person的默认构造函数(它没有显式定义的构造函数)。

任何帮助都是非常感谢的。

Answer 1

最后，我实际上发现了更多的问题，我无法通过前面的答案中的代码方法来解决。这是因为链接器忽略的一些类是ServiceStack.Text程序集的内部类。

最后，我又回到了使用。看起来是这样的：

<?xml version="1.0" encoding="utf-8" ?>
<linker>
  <assembly fullname="ServiceStack.Text">
    <type fullname="ServiceStack.Text.Json.JsonReader`1" >
      <method name="GetParseFn" />
    </type>
    <type fullname="ServiceStack.Text.Common.DeserializeListWithElements`2" >
      <method name="ParseGenericList" />
    </type>
    <type fullname="ServiceStack.Text.Common.WriteListsOfElements`2" >
      <method name="WriteList" />
      <method name="WriteArray" />
    </type>
  </assembly>
</linker>

我在博客上谈到了如何实现这个这里。

Answer 2

事实上，是ServiceStack.Text本身被链接器搞砸了。JsonReader<T>.GetParseFn()是通过反射访问的，这显然导致了它的遗漏。

我已经删除了，并添加了一个类似于以下内容的类：

using ServiceStack.Text.Common;
using ServiceStack.Text.Json;

namespace MyApp
{
    public class LinkerInclude
    {
        public ParseStringDelegate IncludeJsonReader<T>()
        {
            return JsonReader<T>.GetParseFn();
        }
    }
}