在不使用私有 API 的情况下获取当前的第一响应者 [英] Get the current first responder without using a private API

问题描述

我在一个多星期前提交了我的应用程序，今天收到了可怕的拒绝电子邮件.它告诉我我的应用程序无法被接受，因为我使用的是非公共 API；具体来说，它说，

I submitted my app a little over a week ago and got the dreaded rejection email today. It tells me that my app cannot be accepted because I'm using a non-public API; specifically, it says,

您的应用程序中包含的非公共 API 是 firstResponder.

The non-public API that is included in your application is firstResponder.

现在，有问题的 API 调用实际上是我在 SO 上找到的解决方案:

Now, the offending API call is actually a solution I found here on SO:

UIWindow *keyWindow = [[UIApplication sharedApplication] keyWindow];
UIView   *firstResponder = [keyWindow performSelector:@selector(firstResponder)];

如何在屏幕上显示当前的第一响应者?我正在寻找一种不会让我的应用被拒绝的方法.

How do I get the current first responder on the screen? I'm looking for a way that won't get my app rejected.

推荐答案

在我的一个应用程序中，我经常希望第一响应者在用户点击背景时辞职.为此，我在 UIView 上写了一个类别，在 UIWindow 上调用.

In one of my applications I often want the first responder to resign if the user taps on the background. For this purpose I wrote a category on UIView, which I call on the UIWindow.

以下内容基于此，应返回第一响应者.

The following is based on that and should return the first responder.

@implementation UIView (FindFirstResponder)
- (id)findFirstResponder
{
    if (self.isFirstResponder) {
        return self;        
    }
    for (UIView *subView in self.subviews) {
        id responder = [subView findFirstResponder];
        if (responder) return responder;
    }
    return nil;
}
@end

iOS 7+

- (id)findFirstResponder
{
    if (self.isFirstResponder) {
        return self;
    }
    for (UIView *subView in self.view.subviews) {
        if ([subView isFirstResponder]) {
            return subView;
        }
    }
    return nil;
}

斯威夫特:

extension UIView {
    var firstResponder: UIView? {
        guard !isFirstResponder else { return self }

        for subview in subviews {
            if let firstResponder = subview.firstResponder {
                return firstResponder
            }
        }

        return nil
    }
}

Swift 中的使用示例:

if let firstResponder = view.window?.firstResponder {
    // do something with `firstResponder`
}

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