Find View that is the firstresponder

问题:

I would like to get the view that is the first responder, currently I have a UITableView that contains UITextFields, using a method:

-(UIView*) findFirstResponder
{

}

I would like to be able to get the view that is the firstResponder and then do something with that view.

Any ideas?

回答1:

All I had to do was

@implementation UIView (FindViewThatIsFirstResponder)
- (UIView *)findViewThatIsFirstResponder
{
    if (self.isFirstResponder) {        
        return self;     
    }

    for (UIView *subView in self.subviews) {
        UIView *firstResponder = [subView findViewThatIsFirstResponder];
        if (firstResponder != nil) {
            return firstResponder;
        }
    }

    return nil;
}
@end

回答2:

Use UIControl as a root reference to different types of control that can become first responder.

UIControl *currentControl;

As Gobot says - whenever a textfield becomes first responder, keep a note of which one it is...

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField {   

    currentControl = textField;

    . . .

回答3:

There is no simple way to find firstResponder in iOS. The answers above are only tracking UIViews but all subclasses of UIResponder such as UIViewController can be a first responder.

According to the Quick Help of UIResponder:

Many key objects are also responders, including the UIApplication object, UIViewController objects, and all UIView objects (which includes UIWindow). As events occur, UIKit dispatches them to your app's responder objects for handling.

And the only way to follow UIResponder chain will be using UIResponder's next: UIResponder property.

Returns the next responder in the responder chain, or nil if there is no next responder. The UIResponder class does not store or set the next responder automatically, so this method returns nil by default. Subclasses must override this method and return an appropriate next responder. For example, UIView implements this method and returns the UIViewController object that manages it (if it has one) or its superview (if it doesn’t). UIViewController similarly implements the method and returns its view’s superview. UIWindow returns the application object. UIApplication returns nil.

In the most UIKit object superview, UIViewController, UIWindow, UIApplication or Appdelegate will be the next UIResponder.

extension UIResponder {
    func findFirstResponder() -> UIResponder? {
        var responder: UIResponder? = self
        while responder != nil {
            guard let r = responder, r.isFirstResponder() else {
                responder = responder?.next
                continue
            }
            return r
        }
        return nil
    }
}

However the above doesn't track responder's siblings. I guess if you really want to track them all, you need to check the type of responder and track its child(subview, child view controller).

回答4:

I would like to shared with you my implementation for find first responder in anywhere of UIView. I hope it helps and sorry for my english. Thanks

+ (UIView *) findFirstResponder:(UIView *) _view {
   if ([subView isFirstResponder])
      return subView;
   if ([subView isKindOfClass:[UIView class]]) {
      UIView *v = subView;

      if ([v.subviews count] > 0) {
         retorno = [self findFirstResponder:v];
         if ([retorno isFirstResponder]) {
             return retorno;
         }
      }
   }
}