Question

I want to create a password-protected android application. The password should be asked when the task is started or when it comes to foreground.

The complex part is that my app can invoke device inbuilt camera application to capture photo/video, so I cannot control that activity.

So the behavior should be that whenever user starts/returns to my app then password should be asked except for the scenario when he is returning from camera that I sent him to in the first place.

I have thought following ideas, but none of them solve my problem completely, the best one I could think of is

1) Set a flag(flagA) while sending the user to camera, then in a service keep checking that the foreground app is our app. When the foreground app is not our app then set another flag(flagB) to indicate that our app has gone to background. When the app in foreground is our app again, then check if flagA is false (we didnt send him to camera) and flagB is true (app is coming from background). Then show the password screen

Problems
1) The polling interval must be small like 3-4 seconds, so that foreground is detected quickly. This drains the battery.

Thanks

Answer 1

I have solved the problem partially
1) Have a static long variable to track the time between onPause() and onResume(). During normal app operation this time is under 1 second, but if app goes to background and comes to foreground then this duration is more than 1 second. So in onResume() if the duration is more than 1 second then show the Password screen.

2) To handle the camera problem I am having a flag to detect whether I opened the camera, if that flag is set then dont ask for password in onResume().

This solution is not fool proof but works in most scenarios.