Android Lock Screen Widget

Lock screen interaction is difficult. Android allows basic operations with two window flags (FLAG_SHOW_WHEN_LOCKED and FLAG_DISMISS_KEYGUARD). FLAG_SHOW_WHEN_LOCKED works pretty consistently in that it will show on top of the lock screen even when security is enabled (the security isn’t bypassed, you can’t switch to another non-FLAG_SHOW_WHEN_LOCKED window).

If you’re just doing something temporary, like while music is playing or similar, you’ll probably mostly be okay. If you’re trying to create a custom lock screen then there’s a lot of unusual interactions on all the different android platforms. (“Help! I can’t turn off my alarm without rebooting my HTC phone”).

getWindow().addFlags(WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED);
getWindow().addFlags(WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD);

http://developer.android.com/reference/android/view/WindowManager.LayoutParams.html

FLAG_SHOW_WHEN_LOCKED

Window flag: special flag to let windows be shown when the screen is
locked.

FLAG_DISMISS_KEYGUARD

Window flag:
when set the window will cause the keyguard to be
dismissed, only if it is not a secure
lock keyguard. Because such a keyguard
is not needed for security, it will
never re-appear if the user navigates
to another window (in contrast to
FLAG_SHOW_WHEN_LOCKED, which will only
temporarily hide both secure and
non-secure keyguards but ensure they
reappear when the user moves to
another UI that doesn’t hide them). If
the keyguard is currently active and
is secure (requires an unlock pattern)
than the user will still need to
confirm it before seeing this window,
unless FLAG_SHOW_WHEN_LOCKED has also
been set.
Constant Value: 4194304 (0x00400000)

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