从Visual Studio 2017 15.5.1开始，如何不再使用Xamarin.Forms项目来定位具有PCL的最低Android KitKat（API 19）？ [英] As of Visual Studio 2017 15.5.1, How Does One Create a Xamarin.Forms Project to Target Minimum Android KitKat (API 19) with PCL now obsolete?

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问题描述

我想知道如何创建一个针对最低版本的Android Kitkat（API 19）的Xamarin.Forms项目，而无需使用Shared Project选项。



。不能使用Net Standard Library，因为



请注意，PCL现在已在 Xamarin论坛以及 Visual Studio开发者社区



主要支持问题：


  1. 带有最新的V 2017年，使用Xamarin.Forms仍可以进行PCL吗？以及如何？

  2. 如果是，创建基于PCL的Xamarin.Forms项目的步骤是什么，是否有开放源码的模板可以对此进行引导？

  3. 如果否，是否表示我只能使用共享项目代码共享策略/模板通过Xamarin.Forms支持Android KitKat？


解决方案


  • Forms支持Android 4.0.3（API 15）或更高版本，您在混淆 目标框架 >（ compileSdkVersion ）与 目标Android版本（ targetSdkVersion ）与最低Android版本 （ minSdkVersion ）。




    • 您的 Xamarin.Form 项目必须使用以下目标框架牛轧糖/7.0（ MonoAndroid7.0 ）或更高版本，但可以定位最低4.0.3 / IceCreamSandwich版本。




      • 注意：最新版本的Forms要求目标框架为8.0


    • Xamarin有一个很好的指南，它解释了这些东西与Android和 Xamarin.Android

      的关系。



  • Microsoft完全删除了用于创建基于PCL的库的模板选项




    • PCL项目仍然可以正常构建


    • NetStandard是唯一的未来，PCL已经死了，等等，等等...


    • 恕我直言，这是一项重大突破我的许多客户还没有准备好转换为NetStd，并且仍然有NetStd错误（主要是边缘情况）到处浮现


    • 仍然需要创建PCL库，抓取一个现有项目并复制，剥离并重命名...或自己创建 .csproj （请参阅基本的 .csproj ）。





基本配置文件111 PCL .csproj ：



 <？xml version = 1.0 encoding = utf- 8？> 
< Project DefaultTargets = Build ToolsVersion = 4.0 xmlns = http://schemas.microsoft.com/developer/msbuild/2003> 
< PropertyGroup> 
< Configuration Condition =‘$（Configuration）’==’’> Debug< / Configuration> 
< Platform Condition ='$（Platform）'==’’> AnyCPU< / Platform> 
< ProjectGuid> {C38DBA87-39CB-4FD5-B409-6D19E6ED54C8}< / ProjectGuid> 
< ProjectTypeGuids> {786C830F-07A1-408B-BD7F-6EE04809D6DB}; {FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}< / ProjectTypeGuids> 
< UseMSBuildEngine> true< / UseMSBuildEngine> 
< OutputType> Library< / OutputType> 
< RootNamespace> PCLTemplate< / RootNamespace> 
< AssemblyName> PCLTemplate< / AssemblyName> 
< TargetFrameworkVersion> v4.5< / TargetFrameworkVersion> 
< TargetFrameworkProfile> Profile111< / TargetFrameworkProfile> 
< / PropertyGroup> 
< PropertyGroup Condition = =（$ Configuration）| $（Platform）'=='Debug | AnyCPU'> 
< DebugSymbols> true< / DebugSymbols> 
< DebugType>完整< / DebugType> 
< Optimize> false< / Optimize> 
< OutputPath> bin\Debug< / OutputPath> 
< DefineConstants> DEBUG;< / DefineConstants> 
< ErrorReport>提示< / ErrorReport> 
< WarningLevel> 4< / WarningLevel> 
< / PropertyGroup> 
< PropertyGroup Condition = = $（Configuration）| $（Platform）'==‘Release | AnyCPU'> 
< Optimize> true< / Optimize> 
< OutputPath> bin\Release< / OutputPath> 
< ErrorReport>提示< / ErrorReport> 
< WarningLevel> 4< / WarningLevel> 
< / PropertyGroup> 
< ItemGroup> 
< Compile Include = MyClass.cs /> 
< Compile Include = Properties\AssemblyInfo.cs /> 
< / ItemGroup> 
<导入项目= $（MSBuildExtensionsPath32）\Microsoft\Portable\ $（TargetFrameworkVersion）\Microsoft.Portable.CSharp.targets /> 
< / Project>


I want to know how to create a Xamarin.Forms Project that targets minimum version of Android Kitkat (API 19), without using the Shared Project option.

.Net Standard Library is not an option since the minimum supported Android version is Nougat. A large percentage of my target users (more than 40%) still uses phones with an Android version lower than Nougat.

In Visual Studio 15.5.1 or greater, no PCL option is provided under the Code Sharing Strategy Section in creating a new Xamarin.Forms project when using the Cross-Platform App template.

It was noted that PCL is now deprecated on Xamarin's Forum and also on the Visual Studio Developer Community

Key Supporting Questions:

  1. With the latest Vs 2017, is PCL even still possible with Xamarin.Forms? And How?
  2. If Yes, What are the steps to create a PCL-Based Xamarin.Forms Project and are there any open-soured templates to bootstrap this?
  3. If No, Does this mean I can only support Android KitKat with Xamarin.Forms using the Shared-Project Code Sharing strategy/template?

解决方案

  • Forms supports Android 4.0.3 (API 15) and higher, you are confusing the "Target Framework" (compileSdkVersion) for the "Target Android Version" ( targetSdkVersion) vs the "Minimum Android Version" (minSdkVersion).

    • Your Xamarin.Form project has to use the target framework of Nougat/7.0 (MonoAndroid7.0) or above but can target the minimum of 4.0.3/IceCreamSandwich version.

      • Note: The latest version of Forms required a target framework of 8.0

    • Xamarin has a great guide that explains how those things relate from Android to Xamarin.Android

  • Microsoft completely removed the template option to create PCL-based libraries

    • PCL projects still build fine

    • NetStandard is the only future, PCLs are dead, etc, etc...

    • IMHO this was breaking change as a lot of my clients are not ready to convert to NetStd and there are still NetStd bugs floating around (edge cases mostly)

    • Still need to create a PCL library, grab an existing project and copy, strip and rename it... or create the .csproj yourself (see basic .csproj).

A Basic Profile111 PCL .csproj:

<?xml version="1.0" encoding="utf-8"?>
<Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup>
    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
    <ProjectGuid>{C38DBA87-39CB-4FD5-B409-6D19E6ED54C8}</ProjectGuid>
    <ProjectTypeGuids>{786C830F-07A1-408B-BD7F-6EE04809D6DB};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
    <UseMSBuildEngine>true</UseMSBuildEngine>
    <OutputType>Library</OutputType>
    <RootNamespace>PCLTemplate</RootNamespace>
    <AssemblyName>PCLTemplate</AssemblyName>
    <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
    <TargetFrameworkProfile>Profile111</TargetFrameworkProfile>
  </PropertyGroup>
  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
    <DebugSymbols>true</DebugSymbols>
    <DebugType>full</DebugType>
    <Optimize>false</Optimize>
    <OutputPath>bin\Debug</OutputPath>
    <DefineConstants>DEBUG;</DefineConstants>
    <ErrorReport>prompt</ErrorReport>
    <WarningLevel>4</WarningLevel>
  </PropertyGroup>
  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
    <Optimize>true</Optimize>
    <OutputPath>bin\Release</OutputPath>
    <ErrorReport>prompt</ErrorReport>
    <WarningLevel>4</WarningLevel>
  </PropertyGroup>
  <ItemGroup>
    <Compile Include="MyClass.cs" />
    <Compile Include="Properties\AssemblyInfo.cs" />
  </ItemGroup>
  <Import Project="$(MSBuildExtensionsPath32)\Microsoft\Portable\$(TargetFrameworkVersion)\Microsoft.Portable.CSharp.targets" />
</Project>

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