How to get OSX app that is currently receiving key events
I am following the cocoa documentation to determine the current main application in OSX - for example an application that receives key events. However, when I execute the following quick API, the API always returns the same value to me - XCode
but it never changes to chrome
or any other application when switching to them. I also tried to execute the compiled program, but instead of showing constantly XCode
, it now shows which terminal application I am running.
What's the correct way to define an application that receives key events from OSX? Is my code broken in this regard?
import Cocoa
func getActiveApplication() -> String{
// Return the localized name of the currently active application
let ws = NSWorkspace.sharedWorkspace()
let frontApp = ws.frontmostApplication
return frontApp.localizedName
}
var frontMostApp : String
while true {
frontMostApp = getActiveApplication();
NSLog("front app: %@", frontMostApp)
sleep(1);
}
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You have to do one thing differently, that is, follow the NSWorkSpace notifications that tell you that apps have resigned or become active. This is especially important since you are working in debug mode. In debug mode, Xcode creates the app as a child process. In release mode, it basically does the same thing that invokes the open command in the terminal. In debug mode, if you call this code too early and only once, you won't catch the changes. Remember this dynamically.
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This thread is a little outdated but was very helpful. I did some research based on the post by Marco and the answer from the uhukaka. Below is the result.
// swift 3.0
// compile: xcrun -sdk macosx swiftc -framework Cocoa foo.swift -o foo
// run: ./foo
import Cocoa
class MyObserver: NSObject {
override init() {
super.init()
NSWorkspace.shared().notificationCenter.addObserver(self,
selector: #selector(printMe(_:)),
name: NSNotification.Name.NSWorkspaceDidActivateApplication,
object:nil)
}
dynamic private func printMe(_ notification: NSNotification) {
let app = notification.userInfo!["NSWorkspaceApplicationKey"] as! NSRunningApplication
print(app.localizedName!)
}
}
let observer = MyObserver()
RunLoop.main.run()
I am new to both Cocoa and Swift. I don't know if this is effective, but it works for me. I got help from How to create a minimal daemon process in swift 2 command line tool? and Swift 3 NSNotificationCenter Keyboardwillshow / hide among many others.
Swift 4:
NSWorkspace.shared.notificationCenter.addObserver(self, // HERE, shared
selector: #selector(printMe(_:)),
name: NSWorkspace.didActivateApplicationNotification, // HERE
object:nil)
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