I am interested in building a custom lock screen app but would like to integrate into the built in system password lock screen.
My design idea is that the user would set a system password using the standard lock screen in android and my custom lock screen app would be given permission to bypass the standard lock screen and present them with a custom alternative way to unlock the device.
The user would be given the ability to fall back to the system lock screen if they wish. Also, this will give some leniency to my custom app just in case it does not work for whatever reason and woud allow a secure fallback to a system lock screen.
Is this possible in later versions of the Android SDK?
The short answer is no. You cannot edit the native android lock screens and security features related to them with the android sdk. You can however build your own and have that used if the native android lock screen is disabled, if it isn't you end up with two lock screens.
It may be possible to integrate in a minimal way with the "insecure" android lockscreen ie. swipe to unlock, which does not provide any security whatsoever.