inputAccessoryView animating down when alertContro

问题:

I have an inputAccessoryView for a chat app that always remains visible and docked at the bottom of the screen for text input similar to most messaging apps.

When I present an alertController with actionSheet style, the inputAccessoryView animates down off screen as the alert is presented and then back up again when the alert is dismissed. This in turn scrolls my tableView and is undesirable.

This is happening because the chat viewController is giving up firstResponder when the alert is presented.

Is there anyway to present an alertController and not give up firstResponder, or anyway to keep an inputAccessoryView docked at the bottom of the screen when it's view resignsFirstResponder?

回答1:

The InputAccessoryView sits outside of your ViewController's hierarchy - it's contained in the UITextEffectsWindow whose rootViewController is a UIInputWindowController. Similarly the keyboard is contained in UIRemoteKeyboardWindow and its own UIInputWindowController.

So, if we present the alert from the topmost window or higher (UITextEffectsWindow or UIRemoteKeyboardWindow), it won't resign first responder.

The simplest solution I've found is:

let topViewController = UIApplication.shared.windows.last!.rootViewController! topViewController.present(alert, animated: true, completion: nil)

Ideally you would safely handle those optionals. A potentially better solution (I've seen some console errors from the previous solution) would be to create a new UIWindow with a higher WindowLevel, make it the key window and visible, and present the alert from there.

回答2:

For those looking the Objective-C equivalent of Corey's answer:

UIViewController *objViewController = [UIApplication sharedApplication].windows.lastObject.rootViewController;
[objViewController presentViewController:view animated:YES completion:nil];