I develop an iOS Keyboard extension, and I'm using scroll gestures on keyboard. Sometimes when using the keyboard I scroll up the control center and my keyboard stops working fine. Is there any way to detect if control center become visible, or invisible?
You can't do it directly. The most you can know is that your app was deactivated and then activated again. It could be because of the control center, it could be because of the notification center, it could be because a phone call came in, it could be because the user went into the app switcher and came back again...
Here is the possible work around you can try:
It is the UIWindow subclass to enable behavior like adaptive round-corners & detecting when Control Center is opened. This UIWindow subclass does probably the thing you want. You simply subscribe to an NSNotification and can react to the user opening Control Center. Detailed instructions and setup on Github
https://github.com/aaronabentheuer/AAWindow
[AAWindow: The way this is accomplished is by using a combination of NSTimer and overwriting sendEvent in UIWindow to receive all touches without blocking them. So you basically receive all touches check if they are near the lower edge of the screen, if yes set a timer for a half a second and if during this timer is running applicationWillResignActive is called you can be almost certain that ControlCenter is opened. The time has to vary if there's no statusbar, because then the app is in fullscreen and it can take the user up to 3 seconds to launch Control Center.]
Hope it would help you figure out the exact solution to your problem.