Problem :
Error:Could not find com.android.support.constraint:constraint-layout:1.0.0-alpha2.
Required by:
myapp:app:unspecified
My problem was, that the SDK Tools updated it to the latest version, in my case it was 1.0.0-alpha9, but in my gradle dependency was set to
compile 'com.android.support.constraint:constraint-layout:1.0.0-alpha8' So, you can change your gradle build file to
compile 'com.android.support.constraint:constraint-layout:1.0.0-alpha9' Or you check "Show package details" in the SDK Tools Editor and install your needed version. See screenshow below. Image of SDK Tools