Get the current first responder without using a private API

Question

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; specif

Answer 1

For a Swift 3 & 4 version of nevyn's answer:

UIApplication.shared.sendAction(#selector(UIView.resignFirstResponder), to: nil, from: nil, for: nil)

Answer 2

I have a slightly different approach than most. Rather than iterate through the collection of views looking for the one that has isFirstResponder set, I too send a message to nil, but I store the receiver of the message so I can return it and do whatever I wish with it.

import UIKit

private var _foundFirstResponder: UIResponder? = nil

extension UIResponder {

    static var first:UIResponder? {

        // Sending an action to 'nil' implicitly sends it to the first responder
        // where we simply capture it and place it in the _foundFirstResponder variable.
        // As such, the variable will contain the current first responder (if any) immediately after this line executes
        UIApplication.shared.sendAction(#selector(UIResponder.storeFirstResponder(_:)), to: nil, from: nil, for: nil)

        // The following 'defer' statement runs *after* this getter returns,
        // thus releasing any strong reference held by the variable immediately thereafter
        defer {
            _foundFirstResponder = nil
        }

        // Return the found first-responder (if any) back to the caller
        return _foundFirstResponder
    }

    @objc func storeFirstResponder(_ sender: AnyObject) {

        // Capture the recipient of this message (self), which is the first responder
        _foundFirstResponder = self
    }
}

With the above, I can resign the first responder by simply doing this...

UIResponder.first?.resignFirstResponder()

But since my API actually hands back whatever the first responder is, I can do whatever I want with it.

Here's an example that checks if the current first responder is a UITextField with a helpMessage property set, and if so, shows it in a help bubble right next to the control. We call this from a 'Quick Help' button on our screen.

func showQuickHelp(){

    if let textField   = UIResponder?.first as? UITextField,
       let helpMessage = textField.helpMessage {
    
        textField.showHelpBubble(with:helpMessage)
    }
}

The support for the above is defined in an extension on UITextField like so...

extension UITextField {
    var helpMessage:String? { ... }
    func showHelpBubble(with message:String) { ... }
}

Now to support this feature, all we have to do is decide which text fields have help messages and the UI takes care of the rest for us.

Answer 3

Peter Steinberger just tweeted about the private notification UIWindowFirstResponderDidChangeNotification, which you can observe if you want to watch the firstResponder change.

Answer 4

If you just need to kill the keyboard when the user taps on a background area why not add a gesture recognizer and use it to send the [[self view] endEditing:YES] message?

you can add the Tap gesture recogniser in the xib or storyboard file and connect it to an action,

looks something like this then finished

- (IBAction)displayGestureForTapRecognizer:(UITapGestureRecognizer *)recognizer{
     [[self view] endEditing:YES];
}

Answer 5

Here is a Extension implemented in Swift based on Jakob Egger's most excellent answer:

import UIKit

extension UIResponder {
    // Swift 1.2 finally supports static vars!. If you use 1.1 see: 
    // http://stackoverflow.com/a/24924535/385979
    private weak static var _currentFirstResponder: UIResponder? = nil
    
    public class func currentFirstResponder() -> UIResponder? {
        UIResponder._currentFirstResponder = nil
        UIApplication.sharedApplication().sendAction("findFirstResponder:", to: nil, from: nil, forEvent: nil)
        return UIResponder._currentFirstResponder
    }
    
    internal func findFirstResponder(sender: AnyObject) {
        UIResponder._currentFirstResponder = self
    }
}

---

Swift 4

import UIKit    

extension UIResponder {
    private weak static var _currentFirstResponder: UIResponder? = nil
    
    public static var current: UIResponder? {
        UIResponder._currentFirstResponder = nil
        UIApplication.shared.sendAction(#selector(findFirstResponder(sender:)), to: nil, from: nil, for: nil)
        return UIResponder._currentFirstResponder
    }
    
    @objc internal func findFirstResponder(sender: AnyObject) {
        UIResponder._currentFirstResponder = self
    }
}

Answer 6

Here's a solution which reports the correct first responder (many other solutions won't report a UIViewController as the first responder, for example), doesn't require looping over the view hierarchy, and doesn't use private APIs.

It leverages Apple's method sendAction:to:from:forEvent:, which already knows how to access the first responder.

We just need to tweak it in 2 ways:

• Extend UIResponder so it can execute our own code on the first responder.
• Subclass UIEvent in order to return the first responder.

Here is the code:

@interface ABCFirstResponderEvent : UIEvent
@property (nonatomic, strong) UIResponder *firstResponder;
@end

@implementation ABCFirstResponderEvent
@end

@implementation UIResponder (ABCFirstResponder)
- (void)abc_findFirstResponder:(id)sender event:(ABCFirstResponderEvent *)event {
    event.firstResponder = self;
}
@end

@implementation ViewController

+ (UIResponder *)firstResponder {
    ABCFirstResponderEvent *event = [ABCFirstResponderEvent new];
    [[UIApplication sharedApplication] sendAction:@selector(abc_findFirstResponder:event:) to:nil from:nil forEvent:event];
    return event.firstResponder;
}

@end