Application should reopen window

Posted on June 17, 2020

A Mac app created by the default macOS Xcode template will release the main window when it is closed. This makes it impossible to reopen the window unless certain features are added to the app.

app reopen

In the AppDelegate, prevent the window from being released by setting the isReleasedWhenClosed property to false.

func applicationDidFinishLaunching(_ aNotification: Notification) {
    // ...

    // Prevent window from being released once it's closed.
    window.isReleasedWhenClosed = false

Next, use the applicationShouldHandleReopen method in the AppDelegate to handle the reopening of the main app window. You should now be able to reopen the window by clicking the app’s Dock icon.

func applicationShouldHandleReopen(_ sender: NSApplication, hasVisibleWindows flag: Bool) -> Bool {
    if flag {
        print("hasVisibleWindows is `true`")
    } else {
        print("hasVisibleWindows is `false`")
    return true

Another issue is the main app window is still released if the window is closed then another application is selected (becomes active). To prevent this, in the Info.plist file, set Application can be killed to reclaim memory or other extraordinary circumstances to NO. This is the same as setting NSSupportsAutomaticTermination to NO in the Info.plist file.


Gavin Wiggins © 2020