Invalid value 'armeabi' in $(AndroidSupportedAbis). This ABI is no longer supported. Please update your project properties to remove the old value. If the properties page does not show an 'armeabi' checkbox, un-check and re-check one of the other ABIs and save the changes. DemoApp.Android
<AndroidSupportedAbis>armeabi,armeabi-v7a,x86</AndroidSupportedAbis>
在项目的配置文件*.csproj中找到“AndroidSupportedAbis”部分，然后删除不支持的值，我的是描述里标记的部分，改为重新启动就好了；还有要把下面“AndroidNativeLibrary”对应的armeabi删除。