Android Studio is looking for build tools 26.0.2, but build tools 27.0.3 are already released for Android Oreo 8.1
I'm not quite sure why, but Android Studio no longer installs the build tools in the gradle "app" file. Here is how I fixed it. You get two options.
26.0.2, SDK. :
1) Android Studio. .
2) "" > "" > " " > " " > "Android SDK"
SDK Tools. . Android SDK Build-Tools 26.0.2, .
, , 27.0.3 ( ). Android 27.0.3 gradle. :
1) , 27.0.3 Android SDK ( ).
2) build.gradle. android. , , Android Android ( , , "1: " ). , [yourappname] > app > build.gradle
3) , - " :" com.android.application " . " compileSDKVersion " buildToolsVersion" 27.0.3"
4) , !
, .
;