如何解决UITextView自动滚动冲突及键盘遮挡问题？

Hey there! That auto-scroll behavior in UITextView sure can be a pain when you're trying to handle custom scrolling for keyboard occlusion. Let's break down how to either disable that annoying auto-scroll or switch to a more reliable solution altogether.

Option 1: Disable UITextView's Auto-Scroll #

The built-in auto-scroll triggers when UITextView calls scrollRangeToVisible(_:). To take control, subclass UITextView and add a flag to toggle this behavior:

class CustomTextView: UITextView {
    var shouldBlockAutoScroll = false
    
    override func scrollRangeToVisible(_ range: NSRange) {
        // Only let the system handle scrolling if we haven't blocked it
        if !shouldBlockAutoScroll {
            super.scrollRangeToVisible(range)
        }
    }
}

Then update your scrollToVisible() function to block auto-scroll during your custom scroll, then re-enable it after the animation finishes:

func scrollToVisible() { 
    guard let cursorStart = self.EditArea.selectedTextRange?.start else { return }
    
    // Block system auto-scroll temporarily
    (self.EditArea as? CustomTextView)?.shouldBlockAutoScroll = true
    
    let cursorRect = self.EditArea.caretRect(for: cursorStart)
    let cursortop = self.EditArea.convert(cursorRect.origin, to: self.view) 
    let cursorbottom = cursortop.y + cursorRect.height 
    let bottom = UIScreen.main.bounds.size.height - self.EditArea.textContainerInset.bottom 
    var contentOffset = self.EditArea.contentOffset 
    
    if cursortop.y <= 85 { 
        contentOffset.y -= (85 - cursortop.y)
        self.EditArea.setContentOffset(contentOffset, animated: true) 
    } else if cursorbottom.y >= bottom { 
        contentOffset.y += (cursorbottom.y - bottom)
        self.EditArea.setContentOffset(contentOffset, animated: true) 
    }
    
    // Re-enable auto-scroll after the animation completes
    DispatchQueue.main.asyncAfter(deadline: .now() + 0.3) {
        (self.EditArea as? CustomTextView)?.shouldBlockAutoScroll = false
    }
}

Option 2: A More Reliable Keyboard Occlusion Fix (No Custom Scrolling Needed) #

Instead of fighting with UITextView's auto-scroll, use Apple's recommended approach: adjust the text view's content inset when the keyboard appears. This lets the system handle scrolling automatically, and it's way less error-prone.

Step 1: Register Keyboard Notifications #

Add this to your view controller's viewDidLoad():

override func viewDidLoad() {
    super.viewDidLoad()
    // Listen for keyboard show/hide events
    NotificationCenter.default.addObserver(
        self,
        selector: #selector(keyboardWillShow(_:)),
        name: UIResponder.keyboardWillShowNotification,
        object: nil
    )
    NotificationCenter.default.addObserver(
        self,
        selector: #selector(keyboardWillHide(_:)),
        name: UIResponder.keyboardWillHideNotification,
        object: nil
    )
}

Step 2: Handle Keyboard Events #

Add these callback functions to adjust the content inset:

@objc private func keyboardWillShow(_ notification: Notification) {
    guard let keyboardFrame = notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as? CGRect else { return }
    let keyboardHeight = keyboardFrame.height
    
    // Expand the text view's content inset to account for the keyboard
    EditArea.contentInset = UIEdgeInsets(
        top: 0,
        left: 0,
        bottom: keyboardHeight,
        right: 0
    )
    EditArea.scrollIndicatorInsets = EditArea.contentInset
}

@objc private func keyboardWillHide(_ notification: Notification) {
    // Reset the content inset when the keyboard disappears
    EditArea.contentInset = UIEdgeInsets.zero
    EditArea.scrollIndicatorInsets = UIEdgeInsets.zero
}

Step 3: Clean Up Notifications #

Don't forget to remove the observer when your view controller is deallocated:

deinit {
    NotificationCenter.default.removeObserver(self)
}

Bonus: Ensure Cursor Stays Visible #

If you still want to guarantee the cursor never gets hidden after selection changes, add this UITextView delegate method (make sure your view controller conforms to UITextViewDelegate):

func textViewDidChangeSelection(_ textView: UITextView) {
    guard let selectedRange = textView.selectedTextRange else { return }
    // Let the system scroll the cursor into view (now that content inset is adjusted)
    textView.scrollRangeToVisible(textView.textRange(from: selectedRange.start, to: selectedRange.start)!.nsRange)
}

内容的提问来源于stack exchange，提问作者Sidney Liu