Randy Tong wrote:These two lines should follow the targetSdkVersion.
For me, I set targetSdkVersion as 27, so this line should be
Thank you for the reply.
The thing is implementation 'com.android.support:appcompat-v7:28.0.0' is automatically gernerated when I started a new project. So I assume it is the right version. I use lollipop 5.1 on my Android Studio. The implementation 'com.android.support:support-v4:23.4.0' is I copied from a sample frome a tutorial code which is a few years old. So I assume it is out of date. How do I know which verson goes with 'com.android.support:appcompat-v7:28.0.0'? My SDK Manager looks like this, don't know if it matters.