Android studio should be able to locate dart's sdk afterwards: If ndk.dir is absent, add. It usually happens with projects that were created in other machines.
To fix this on android studio 3.1.3: This is very frustrating because i created a web flutter project and i can run it just fine. All i did was create a new flutter project from vs code and run on my device.
I also wrote an article about integrating flutter local notifications which you can read here. Mention the same version in \android\local.properties file by changing ndk.dir value to the version you get in step 1. And you can see the source code of an application i made which integrated flutter local.