error message

Unable to resolve the dependency for ': app @ the debug/compileClasspath: Could not resolve com. Android. Support. The constraint, the constraint - layout: 2.0.2. & lt; a href="disable.gradle.offline.mode"> Disable offline mode and sync project< /a> < br> < a href="Unable%20to%20resolve%20dependency%20for%20&%20#%2039;%20:app@debug/compileClasspath&%20#%2039;%20:%20Could%20not%20resolve%20com.%20Android.%20Support.%20The%20constraint,%20the%20constraint%20-%20layout:%202.0.2.%20"& gt; Show Details< /a> Affected Modules: < a href="openFile:D:/android3/app/build.gradle"> app< /a>

solution :

change build. Gradle (:app) (note with app suffix)
to