Update your Xamarin to lastest environment for Build Android Project get error

1. Download JDK 1.8 (mustbe Windows x64 version) from Oracle : http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html
2. Change your Xamaarin to use JDK 1.8 by Visual Studio 2015 > Tools > Options > Xamarin > Android > Java Development Kit Location  as following
   
   
3. Upgrade your NuGet package of Xamarin.Forms of all your project.
4. Clean your project and rebuid it.
5. If you still get error for build your Android project, try delete the director : C:\Users\%username%\AppData\Local\Xamarin