Cocoa Listen to the keyboard + command before the event

Question

I am working on a macOS application and I would like to handle the local hotkey event (command + up arrow) in NSViewController .

Here's how I do it with Swift:

 override func keyDown(with event: NSEvent) { let modifierkeys = event.modifierFlags.intersection(.deviceIndependentFlagsMask); let hasCommand = modifierkeys == .command; switch Int(event.keyCode) { case kVK_UpArrow where hasCommand: print("command up"); break; case kVK_ANSI_B where hasCommand: print("command B"); break; default: break; } } 

When I create and press the + up command in the view, the console shows nothing. But when I press the + B command, the “B” command is issued.

So why does this not work for Command + up? How do I achieve this?

Answer 1

I found a solution:

 self.keyMonitor = NSEvent.addLocalMonitorForEvents(matching: NSEventMask.keyDown, handler: { (event) -> NSEvent? in if (event.modifierFlags.contains(.command)){ if (Int(event.keyCode) == kVK_UpArrow){ print("command up"); return nil; } } return event; }); 

The key point is to interrupt the keydown event and prevent it from being dispatched by returning nil