cocoa - 为什么这对其他类或子类不起作用？

Question

我正在尝试获取系统选定文本的边界，我在这里找到了这个方法:

+ (void) getPosition{
    AXUIElementRef systemWideElement = AXUIElementCreateSystemWide();
    AXUIElementRef focussedElement = NULL;
    AXError error = AXUIElementCopyAttributeValue(systemWideElement, kAXFocusedUIElementAttribute, (CFTypeRef *)&focussedElement);

    if (error != kAXErrorSuccess) {
        NSLog(@"Could not get focussed element");
    } else {
        AXValueRef selectedRangeValue = NULL;
        AXError getSelectedRangeError = AXUIElementCopyAttributeValue(focussedElement, kAXSelectedTextRangeAttribute, (CFTypeRef *)&selectedRangeValue);
        if (getSelectedRangeError == kAXErrorSuccess) {
            CFRange selectedRange;
            AXValueGetValue(selectedRangeValue, kAXValueCFRangeType, &selectedRange);
            AXValueRef selectionBoundsValue = NULL;
            AXError getSelectionBoundsError = AXUIElementCopyParameterizedAttributeValue(focussedElement, kAXBoundsForRangeParameterizedAttribute, selectedRangeValue, (CFTypeRef *)&selectionBoundsValue);
            CFRelease(selectedRangeValue);
            if (getSelectionBoundsError == kAXErrorSuccess) {
                CGRect selectionBounds;
                AXValueGetValue(selectionBoundsValue, kAXValueCGRectType, &selectionBounds);
                NSLog(@"Selection bounds: %@", NSStringFromRect(NSRectFromCGRect(selectionBounds)));
            } else {
                NSLog(@"Could not get bounds for selected range");
            }
            if (selectionBoundsValue != NULL) CFRelease(selectionBoundsValue);
        } else {
            NSLog(@"Could not get selected range");
        }
    }
    if (focussedElement != NULL) CFRelease(focussedElement);
    CFRelease(systemWideElement);
}

但是如果我从 appDelegate.m 类以外的任何其他地方调用 if ，它总是返回:

Could not get focussed element

我错过了什么设置？

或者其他人知道如何让系统选择文本位置吗？

Answer 1

您不应该将 focussedvalue (实际上拼写为 focusedvalue)初始化为 AXUIElementRef，然后在将其作为参数传递给AXUIElementCopyAttributeValue。
相反，将其初始化为 CFTypeRef。

尝试一下，并在此处查看示例代码以供引用: https://developer.apple.com/library/mac/samplecode/UIElementInspector/Listings/UIElementUtilities_m.html#//apple_ref/doc/uid/DTS10000728-UIElementUtilities_m-DontLinkElementID_14