java - What's the COMPLETE way to request the user to enable accessibility services?

Question

I have looked in stackoverflow and found only the following:

Intent changeSettings = new Intent(android.provider.Settings.ACTION_ACCESSIBILITY_SETTINGS);
startActivityForResult(changeSettings, 0);

How do I add to this code the ability to check whether the permission is already granted? And what exactly does "shouldShowRequestPermissionRationale()" do and how does it work? Same question for "onRequestPermissionResult".

Thank you.

标签： javaandroidandroid-studio