iOS：JavaScript实现长按按钮唤起系统键盘

Got it, let's tackle this iOS keyboard issue for long-press triggers. You're right that the proxy text field works for regular taps, but the problem with touchstart is rooted in iOS's strict rules around keyboard activation—system-level security prevents keyboard calls from ambiguous touch events where the system hasn't yet confirmed the user's intent (like a touchstart that might still turn into a swipe or tap).

The Reliable Solution: Use a Long Press Gesture Recognizer #

Instead of relying on raw touch events, leverage iOS's UILongPressGestureRecognizer to accurately detect when a long press has occurred. This gesture is explicitly recognized by the system as a user-initiated action, so triggering the keyboard here will be allowed.

Step 1: Set Up Your Proxy Text Field

First, make sure your proxy text field is properly configured and added to the view hierarchy (critical for it to become a first responder):

private let proxyTextField: UITextField = {
    let textField = UITextField()
    textField.isHidden = true
    textField.userInteractionEnabled = true
    // Optional: Set keyboard type if needed
    textField.keyboardType = .default
    return textField
}()

override func viewDidLoad() {
    super.viewDidLoad()
    // Add the proxy text field to your view hierarchy
    view.addSubview(proxyTextField)
    // Position it off-screen if needed (hidden works too, but adding to hierarchy is mandatory)
    proxyTextField.frame = CGRect(x: -1000, y: -1000, width: 0, height: 0)
}

Step 2: Attach the Long Press Gesture to Your Button

Add the gesture recognizer to your target button and handle the long press event:

override func viewDidLoad() {
    super.viewDidLoad()
    // ... existing setup for proxy text field ...
    
    let longPressGesture = UILongPressGestureRecognizer(
        target: self,
        action: #selector(handleButtonLongPress(_:))
    )
    // Adjust minimum press duration if needed (default is 0.5 seconds)
    longPressGesture.minimumPressDuration = 0.5
    yourLongPressButton.addGestureRecognizer(longPressGesture)
}

@objc private func handleButtonLongPress(_ gesture: UILongPressGestureRecognizer) {
    // Only trigger once when the long press starts
    guard gesture.state == .began else { return }
    
    // Activate the keyboard via the proxy text field
    proxyTextField.becomeFirstResponder()
}

Why This Works #

iOS restricts keyboard activation to events that are clearly user-initiated and unambiguous. The UILongPressGestureRecognizer's .began state fires only after the system confirms the user has held the button long enough (passing the minimumPressDuration threshold). This counts as a valid, intentional user interaction, so the system will allow becomeFirstResponder() to trigger the keyboard—unlike touchstart, which is too early in the touch sequence for the system to confirm intent.

Bonus: Clean Up on Long Press End (Optional) #

If you want to dismiss the keyboard when the user releases the button, add handling for the gesture's .ended state:

@objc private func handleButtonLongPress(_ gesture: UILongPressGestureRecognizer) {
    switch gesture.state {
    case .began:
        proxyTextField.becomeFirstResponder()
    case .ended, .cancelled:
        proxyTextField.resignFirstResponder()
    default:
        break
    }
}

内容的提问来源于stack exchange，提问作者Zahlii