Keyboard + text input

How it works

• First responder: becomeFirstResponder() returns Bool — false if not in a window yet or canBecomeFirstResponder is false. Dismiss: resignFirstResponder(), view.endEditing(true), or a nil-targeted resignFirstResponder action.
• inputView replaces the keyboard (a picker); inputAccessoryView rides above it. Chat composer: the VC returns true from canBecomeFirstResponder and vends the bar as its inputAccessoryView; with keyboardDismissMode = .interactive it follows the finger.
• keyboardLayoutGuide (iOS 15): pin to its topAnchor; show/hide, height changes and animation come free; followsUndockedKeyboard for the floating iPad keyboard. With no keyboard it sits at the safe-area bottom.
• Scroll view: inset content + indicators by the overlap minus the bottom safe area (already in the adjusted inset), scrollRectToVisible, reset on hide. UITableViewController does it for you.
• Traits: keyboardType (.emailAddress, .numberPad, .decimalPad, .URL); textContentType drives AutoFill — .username, .password, .newPassword (+ passwordRules), .oneTimeCode (SMS code offered above the keyboard, no permission); returnKeyType; autocorrectionType, smartQuotesType, smartDashesType.
• UITextField: the delegate asks (shouldBeginEditing, shouldChangeCharactersIn with an NSRange in UTF-16, textFieldShouldReturn); control events report (.editingChanged incl. paste/AutoFill, .editingDidEndOnExit; addAction(_:for:)). A programmatic text = triggers neither.
• Hardware keyboard: UIKeyCommand(title:action:input: modifierFlags:) in a responder’s keyCommands (or the buildMenu(with:) menu) — titled ones appear when Cmd is held; wantsPriorityOverSystemBehavior (iOS 15) wins keys the system uses. Raw keys: pressesBegan → UIPress.key. The software keyboard shrinks to a shortcut bar.
• SwiftUI: avoids the keyboard itself (iOS 14; opt out .ignoresSafeArea(.keyboard)). iOS 15: @FocusState + .focused, .submitLabel + .onSubmit, a ToolbarItemGroup(placement: .keyboard); iOS 16 .scrollDismissesKeyboard; iOS 17 .onKeyPress.

Example

// iOS 15+: pin the composer to the keyboard - no observers
composer.bottomAnchor.constraint(
  equalTo: view.keyboardLayoutGuide.topAnchor).isActive = true
// scroll view, from keyboardWillChangeFrame:
@objc func kbChanged(_ n: Notification) {
  guard let end = n.userInfo?[UIResponder
          .keyboardFrameEndUserInfoKey] as? CGRect,
        let screen = view.window?.screen else { return }
  let kb = view.convert(end, from: screen.coordinateSpace)
  let overlap = max(0, view.bounds.maxY - kb.minY
                       - view.safeAreaInsets.bottom)
  scroll.contentInset.bottom = overlap
  scroll.verticalScrollIndicatorInsets.bottom = overlap }
// SwiftUI
TextField("Email", text: $email).focused($field, equals: .email)
  .textContentType(.emailAddress).keyboardType(.emailAddress)
  .submitLabel(.next).onSubmit { field = .password }

Interview traps

• A hard-coded keyboard height, or only willShow: the predictive bar, emoji, hardware or floating keyboard change the frame — handle willChangeFrame, or use the guide.
• Keyboard frame is in screen coordinates; in Split View / Stage Manager the window is not the screen — convert.
• becomeFirstResponder() in viewDidLoad returns false (no window): do it in viewDidAppear. SwiftUI’s twin: setting @FocusState in onAppear can be dropped — defer it.
• Max length in shouldChangeCharactersIn: the range is UTF-16, emoji are several units, and marked text is not final — compute the result with Range(range, in:), skip while markedTextRange != nil.
• Smart quotes / dashes / autocorrect in username, code or search fields silently change " into “ — set .no.
• .numberPad has no Return key: add a Done in the accessory view / keyboard toolbar.

Remember

Responder owns the keyboard · guide beats notifications · read the real frame · marked text is not text yet.

Likely questions

1. Composer glued to the keyboard? — keyboardLayoutGuide, or inputAccessoryView + .interactive.
2. SMS code AutoFill? — textContentType = .oneTimeCode.
3. Next field on Return? — returnKeyType = .next; in textFieldShouldReturn make the next one first responder.
4. Cmd-S on iPad? — UIKeyCommand / .keyboardShortcut("s").