Warning:
Your app currently targets API level 15 and must target at least API level 26 to ensure it is built on the latest APIs optimised for security and performance."
How can I find out what my apps Target API level is, and how can I change it?
Build the apk and install it on your own device(s) to test.
I do not recommend uploading apps built with the current version of DS and targetting api26 to the Google play store unless you have tested the apk on the oldest and newest versions of Android your app allows.
I currently find that copies of my existing apps, when targetting api26 and run on Oreo need me to go into Android settings for the app and manually authorize some permissions.
While they work fine like that, it is clear there will need to be a way to request permissions are granted by the user from within the apps before they are ready to be published.
The minimum build.json to apply the target would be
{
"manifest": {
"targetSdkVersion": "26"
}
}
You need to create a file in the top level of your project called build.json to contain the manifest entry