Hi :
I have been installed My BA4Av10 APP in Android-7 , now i'm installing to another telephones with android-9 , and send me the following message in the phone.
"This application has been created for an older version of android and it may not work well......"
If i put targetSdkversion in manifest, compile and install in the phone the app , changes the objects like edittext , and buttoms, (the view of the objects change)
As @agraham says, the warning that you are seeing in you first post is only a warning; it is not an error. You can ignore it - there is nothing serious that needs fixing. So leave things as they are if you prefer them that way