iOS CTCallCenter Intercepting calls from your app even from the background
Example
From Apple documentation:
Use the CTCallCenter class to obtain a list of current cellular calls, and to respond to state changes for calls such as from a dialing state to a connected state. Such state changes are known as cellular call events.
The purpose of CTCallCenter is to give the developer the opportunity to pause his app state during a call in order to give the user the best experience.
Objective-C:
First, we will define a new class member inside the class we want to handle the interceptions:
@property (atomic, strong) CTCallCenter *callCenter;
Inside our class init (constructor) we will allocate new memory for our class member:
[self setCallCenter:[CTCallCenter new]];
Afterwards, we will invoke our new method that actually handles the interceptions:
- (void)registerPhoneCallListener
{
[[self callCenter] setCallEventHandler:^(CTCall * _Nonnull call) {
NSLog(@"CallEventHandler called - interception in progress");
if ([call.callState isEqualToString: CTCallStateConnected])
{
NSLog(@"Connected");
}
else if ([call.callState isEqualToString: CTCallStateDialing])
{
NSLog(@"Dialing");
}
else if ([call.callState isEqualToString: CTCallStateDisconnected])
{
NSLog(@"Disconnected");
} else if ([call.callState isEqualToString: CTCallStateIncoming])
{
NSLog(@"Incomming");
}
}];
}
That's it, if the user will use your app and will receive a phone call you could intercept this call and handle your app for a save state.
It is worth mentioning that there are 4 call states you can intercept:
CTCallStateDialing
CTCallStateIncoming
CTCallStateConnected
CTCallStateDisconnected
Swift:
Define your class member at the relevant class and define it:
self.callCenter = CTCallCenter()
self.callCenter.callEventHandler = { call in
// Handle your interception
if call.callState == CTCallStateConnected
{
}
}
What will happen if your app is in the background and you need to intercept calls while the app is in the background ?
For example, if you develop an enterprise app you can basically just add 2 capabilities (VOIP & Background fetch) in the Capabilities tab:
Your project target -> Capabilities -> Background Modes -> mark Voice over IP & Background fetch
