Everytime I open an XML layout file, the following error message displays:
An internal error occurred during: \"Check Android SDK\".
java.util.ConcurrentModificati
Well your code is fine and I'm not sure why there is an error. There is some thing you can try as the error asks you to check "android SDK"
In the menu bar
Select tools>-android>-SDK manager
and download the SDK build tools, SDK platform and Google API's for the target SDK version of your project.Make sure you have downloaded all the new updates, if any
if you are not sure which items you have to download , you can select all of them.(will take more time to download of course).no harm in trying
Restart the IDE
You can find more info here: https://developer.android.com/sdk/installing/adding-packages.html