"The specified Android SDK Build Tools version (26.0.0) is ignored..."

Here if you are referring to my previous answers Here is an Update. 1. Compile would be removed from the dependencies after 2018.

a new version build Gradle is available.

Use the above-noted stuff it will help you to resolve the errors. It is needed for the developers who are working after March 2018. Also, maven update might be needed. All above answers will not work on the Android Studio 3.1. Hence Above code block is needed to be changed if you are using 3.1. See also I replaced compile by implementation.

Open app/build.gradle file

Change buildToolsVersion to buildToolsVersion "26.0.2"

change compile 'com.android.support:appcompat to compile 'com.android.support:appcompat-v7:26.0.2'

Solution to this problem is simple

Go to build.gradle (module.app) file

It will help us to rebuild gradle for the project, to make it sync again.

Update to Android Studio 3.0.1 which treats these as warnings. Android 3.0 was treating such warnings as errors and hence causing the gradle sync operation to fail.