You can solve the problem changing the compileSdkVersion in the Grandle.build file from 18 to wtever SDK is installed ..... BUTTTTT
If you are trying to goin back in SDK versions like 18 to 17 ,You can not use the feature available in 18 or 18+
If you are migrating your project (Eclipse to Android Studio ) Then off course you Don't have build.gradle file in your Existed Eclipse project
So, the only solution is to ensure the SDK version installed or not, you are targeting to , If not then install.
Error:Cause: failed to find target with hash string 'android-19' in: C:\Users\setia\AppData\Local\Android\sdk