Mac OS下AXUIElementCopyAttributeValue解包问题求助

Hey there! Let's break down what's going wrong here and fix that error you're hitting with AXUIElementCopyAttributeValue.

What's Causing the Issue? #

You've got two key problems here:

1. Incorrect pointer handling: The way you're passing the position variable to the API is invalid — you can't force-cast a nil optional to a mutable pointer like that.
2. Mismatched accessibility element: You're trying to get the kAXPositionAttribute from an application-level accessibility element (created via AXUIElementCreateApplication), but this attribute only exists on individual window elements, not the app itself.

Step-by-Step Fixes #

1. Fix the Pointer Passing #

AXUIElementCopyAttributeValue expects a writable pointer to store the result. In Swift, you don't need to manually cast to UnsafeMutablePointer — just declare a mutable CFTypeRef? variable and pass it with the & operator, which gives the API a reference to write to.

Bad code:

var position : CFTypeRef? = nil
let res : AXError = AXUIElementCopyAttributeValue(windowAccessibilityElem, kAXPositionAttribute as CFString, position as! UnsafeMutablePointer<CFTypeRef?>)

Fixed code:

var position: CFTypeRef?
let res: AXError = AXUIElementCopyAttributeValue(windowAccessibilityElem, kAXPositionAttribute as CFString, &position)

2. Target the Correct Accessibility Element #

Since kAXPositionAttribute belongs to window elements, you first need to fetch the list of windows from the application element, then query each window's position.

Here's the full corrected code snippet:

for entry in windowList! as Array {
    let ownerName: String = entry.object(forKey: kCGWindowName) as? String ?? "N/A"
    let ownerPID: Int = entry.object(forKey: kCGWindowOwnerPID) as? Int ?? 0
    let pid = Int32(ownerPID)
    
    // Create accessibility element for the application
    let appAccessibilityElem: AXUIElement = AXUIElementCreateApplication(pid)
    
    // First, get the list of windows from the app
    var windows: CFTypeRef?
    let getWindowsRes = AXUIElementCopyAttributeValue(appAccessibilityElem, kAXWindowsAttribute as CFString, &windows)
    
    if getWindowsRes == .success, let windowElements = windows as? [AXUIElement] {
        // Loop through each window element to get its position
        for windowElem in windowElements {
            var position: CFTypeRef?
            let positionRes = AXUIElementCopyAttributeValue(windowElem, kAXPositionAttribute as CFString, &position)
            
            if positionRes == .success, let pos = position as? CGPoint {
                print("Window position: \(pos)")
            } else {
                print("Failed to get position, error code: \(positionRes.rawValue)")
            }
        }
    } else {
        print("Failed to fetch windows, error code: \(getWindowsRes.rawValue)")
    }
}

3. Critical Extra Note #

Don't forget that accessibility APIs require permission! You need to:

1. Open System Settings → Privacy & Security → Accessibility
2. Toggle on your app in the list

Without this permission, you'll keep getting AXErrorNotAuthorized no matter how correct your code is.

内容的提问来源于stack exchange，提问作者camelCaseCowboy