小弟最近在自学.net安卓这块，在环境搭建的时候遇到一些问题，我安装Xamarin后，提示“javac.exe”已退出，代码为 2。具体输出如下：
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1>------ 已启动生成: 项目: App5, 配置: Debug Any CPU ------
1> Processing: obj\Debug\res\layout\main.xml
1> Processing: obj\Debug\res\layout\rectanglemain.xml
1> Processing: obj\Debug\res\layout\roundmain.xml
1> Processing: obj\Debug\res\values\strings.xml
1>AAPT : warning : string 'auth_client_needs_enabling_title' has no default translation.
1>AAPT : warning : string 'auth_client_needs_installation_title' has no default translation.
1>AAPT : warning : string 'auth_client_needs_update_title' has no default translation.
1>AAPT : warning : string 'auth_client_play_services_err_notification_msg' has no default translation.
1>AAPT : warning : string 'auth_client_requested_by_msg' has no default translation.
1>AAPT : warning : string 'auth_client_using_bad_version_title' has no default translation.
1>AAPT : warning : string 'auth_client_needs_enabling_title' has no default translation.
1>AAPT : warning : string 'auth_client_needs_installation_title' has no default translation.
1>AAPT : warning : string 'auth_client_needs_update_title' has no default translation.
1>AAPT : warning : string 'auth_client_play_services_err_notification_msg' has no default translation.
1>AAPT : warning : string 'auth_client_requested_by_msg' has no default translation.
1>AAPT : warning : string 'auth_client_using_bad_version_title' has no default translation.
1>AAPT : warning : string 'auth_client_needs_enabling_title' has no default translation.
1>AAPT : warning : string 'auth_client_needs_installation_title' has no default translation.
1>AAPT : warning : string 'auth_client_needs_update_title' has no default translation.
1>AAPT : warning : string 'auth_client_play_services_err_notification_msg' has no default translation.
1>AAPT : warning : string 'auth_client_requested_by_msg' has no default translation.
1>AAPT : warning : string 'auth_client_using_bad_version_title' has no default translation.
1> App5 -> c:\users\opq\documents\visual studio 2015\Projects\App5\App5\bin\Debug\App5.dll
1> Processing: obj\Debug\res\layout\main.xml
1> Processing: obj\Debug\res\layout\rectanglemain.xml
1> Processing: obj\Debug\res\layout\roundmain.xml
1> Processing: obj\Debug\res\values\strings.xml
1> Processing: obj\Debug\res\layout\main.xml
1> Processing: obj\Debug\res\layout\rectanglemain.xml
1> Processing: obj\Debug\res\layout\roundmain.xml
1> Processing: obj\Debug\res\values\strings.xml
1>AAPT : warning : string 'auth_client_needs_enabling_title' has no default translation.
1>AAPT : warning : string 'auth_client_needs_installation_title' has no default translation.
1>AAPT : warning : string 'auth_client_needs_update_title' has no default translation.
1>AAPT : warning : string 'auth_client_play_services_err_notification_msg' has no default translation.
1>AAPT : warning : string 'auth_client_requested_by_msg' has no default translation.
1>AAPT : warning : string 'auth_client_using_bad_version_title' has no default translation.
1>C:\Program Files (x86)\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(1933,3): error MSB6006: “javac.exe”已退出，代码为 2。
我在C:\Program Files (x86)\MSBuild\Xamarin\Android\目录下并没有找不到Xamarin.Android.Common.targets(1933,3)这个组件，在cmd里面查看javac截图如下
