Support Android Studio 3.1

[mravn-google]

Android Studio 3.1 was released on March 26.

• Upgrade project templates to use Android Studio Gradle plugin version 3.1.2 and Gradle version 4.4
• Update documentation on how to open a plugin project for editing in Android Studio (importing the example/android/build.gradle file no longer works)

[mravn-google]

@mit @Hixie @devoncarew Upgrading the project templates means they stop working in Android Studio 3.0.1. Not upgrading means (at least) users will be met with a dialog saying

To take advantage of all the latest features (such as Instant Run), improvements and security fixes, we strongly recommend that you update the Android Gradle plugin to version 3.1.2 and Gradle to version 4.4.

upon opening the android/ folder of a Flutter project in Android Studio 3.1. It appears that accepting to update works.

[mravn-google]

It appears that one can open a plugin project by just opening the example/android folder with AS 3.1.
It further appears that after accepting to update the Gradle stuff, the example project (and the plugin) works.

[devoncarew]

/cc @stevemessick

[zoechi]

Is there still something to do? Seems to work fine and I am not aware of related bug reports.

[stevemessick]

Flutter projects should use Gradle version 4.4. Until they do users are hit with a confusing message (see above). Opening the android folder works fine, as mentioned, and the IDE has support for that.

[zoechi]

Is this still an issue?

[devoncarew]

I think this is addressed.

[github-actions]

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.