How to lock android buttons/phone from code (screen lock)?

Question

I have made a simple Android app with a pin-code/screen lock. The user have to write a password to lock the phone and then repeat it to unlock the phone. The problem is that the user still can press back, home (etc) to exit the app without writeing the code. How can I prevent this?

Answer 1

You can block the back button by overwriting dispatchKeyEvent() in your Activity class, and returning true if event.getKeyCode() is equal to KeyEvent.KEYCODE_BACK. But you cannot block the Home button from going to the home page.

I have heard of some trickery where you register your application as a receiver of the android.intent.category.HOME intent. This would cause the Android OS to load your activity if the user presses the home button. If you can get this to work, you could then load the "actual" home screen if the user has entered the correct password. This approach is likely to behave differently on different devices and Android versions, however, and it probably would do nothing to stop the Hold-Home task list from appearing.

The bottom line is the Android OS has been designed to prevent just the thing you are trying to do: an application should not be able to take control over the phone and prevent other applications (especially the Phone) from running.

Answer 2

It's my understanding that you cannot block the home key as it's a security feature that allows the user to always exit an app. Pressing home will not close the activity however.

Answer 3

the guys who created free "Toddler lock" apk somehow managed to did it - download and see for yourself :)

when you run it, it asks for permission to run as home app and you need to check the box "use as default". To exit from app, you need to press on all 4 corners of the screen. All the buttons but power one are locked. So there is a way for sure to do that!

he explains to users how it works here: http://www.toddlerlock.com/3.html