Unable to migrate Flutter project to AndroidX

I have a Flutter project in Android Studio. I am planning to migrate to AndroidX. Whenever I do Refactor -> Migrate to AndroidX, Android Studio shows error message:

You need to have compileSdk set to at least 28 in your module build.gradle to migrate to AndroidX.

However I have already set the compileSdkVersion 28 in my app/gradle.build file.

Is there anything else I need to do?

Solution

I was able to resolve my issue:

Open the Flutter project into Android Studio
Right click on the android directory, click on Flutter -> Open Android module in Android Studio. It asked me to upgrade my gradle plugin.
Then I installed Google Play Services. Tools -> SDK Manager -> SDK Tools and check the Google Play Services.

After the Google Play Services Installed, I did Refactor -> Migrate to AndroidX. It started working.

Note: Do the refactor from the project window you opened in the step 2.