如何监听UITableViewCell中UITextField的resignFirstResponder事件并实现警告显示与表格高度动态刷新

Hey there! Let's fix up your cell to meet the validation and height refresh requirements. Your current UI setup is solid, but we need to add text field event handling, validation logic, and a way to tell the table view to update the cell's height when the warning label shows up.

Step 1: Make the Cell Handle Text Field Events #

First, we'll have the cell adopt UITextFieldDelegate to detect when the second text field resigns its first responder. We'll also add a closure to notify the parent table view when the validation state changes (so it can refresh the cell height).

Step 2: Add Input Validation Logic #

We'll check if both fields are empty when the second text field finishes editing, and add an extra handler to hide the warning label automatically if the user starts typing in either field.

Step 3: Adjust Constraints for Dynamic Height #

The warning label needs a bottom constraint tied to the cell's content view—this way, its visibility will automatically adjust the cell's total height.

Full Modified Code #

import Foundation
import UIKit
import SnapKit

class TwoTextInputTableViewCell: UITableViewCell, UITextFieldDelegate {
    let firstTextField = UITextField()
    let secondTextField = UITextField()
    let stackView = UIStackView().then {
        $0.axis = .horizontal
        $0.distribution = .fillEqually
        $0.spacing = 15
    }
    let warningLabel = UILabel().then {
        $0.isHidden = true
        $0.addCharacterSpacing(-0.1)
        $0.font = .systemFont(ofSize: 12)
        $0.textColor = UIColor.CommonColor.salmonColor
        $0.text = "Please fill in at least one field!" // Don't forget to set your actual warning text
    }
    
    // Closure to notify parent table view of validation state changes
    var onValidationStateChanged: (() -> Void)?
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setupTextFieldConfig()
    }
    
    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String!) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        setupSubviewsAndConstraints()
        setupTextFieldConfig()
    }
    
    private func setupSubviewsAndConstraints() {
        contentView.addSubviews(stackView, warningLabel)
        stackView.addArrangedSubview(firstTextField)
        stackView.addArrangedSubview(secondTextField)
        
        stackView.snp.makeConstraints {
            $0.left.equalToSuperview().offset(24)
            $0.right.equalToSuperview().offset(-24)
            $0.top.equalToSuperview().offset(12)
            $0.height.equalTo(56)
        }
        
        warningLabel.snp.makeConstraints {
            $0.top.equalTo(stackView.snp.bottom).offset(12)
            $0.height.equalTo(16)
            $0.left.right.equalTo(stackView)
            $0.bottom.equalToSuperview().offset(-12) // Critical: ties warning label to cell bottom
        }
    }
    
    private func setupTextFieldConfig() {
        firstTextField.delegate = self
        secondTextField.delegate = self
        
        // Add text change handlers to auto-hide warning when user types
        firstTextField.addTarget(self, action: #selector(textFieldTextChanged), for: .editingChanged)
        secondTextField.addTarget(self, action: #selector(textFieldTextChanged), for: .editingChanged)
    }
    
    // MARK: - UITextFieldDelegate
    func textFieldDidEndEditing(_ textField: UITextField) {
        // Only trigger validation when the second text field resigns first responder
        guard textField == secondTextField else { return }
        validateInputFields()
    }
    
    // MARK: - Input Validation
    @objc private func textFieldTextChanged() {
        validateInputFields()
    }
    
    private func validateInputFields() {
        // Trim whitespace to avoid treating empty spaces as valid content
        let firstIsEmpty = firstTextField.text?.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty ?? true
        let secondIsEmpty = secondTextField.text?.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty ?? true
        
        let shouldShowWarning = firstIsEmpty && secondIsEmpty
        warningLabel.isHidden = !shouldShowWarning
        
        // Notify parent table view to update cell height
        onValidationStateChanged?()
    }
}

Step 4: Configure the Parent Table View #

In your view controller, enable automatic row heights and set up the closure to trigger smooth height updates:

class YourViewController: UIViewController {
    @IBOutlet weak var tableView: UITableView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Enable automatic cell height calculation
        tableView.rowHeight = UITableView.automaticDimension
        tableView.estimatedRowHeight = 100 // Set a reasonable estimated height
        tableView.register(TwoTextInputTableViewCell.self, forCellReuseIdentifier: "TwoTextInputCell")
    }
}

extension YourViewController: UITableViewDataSource {
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "TwoTextInputCell", for: indexPath) as! TwoTextInputTableViewCell
        
        // Set up closure to refresh cell height when validation state changes
        cell.onValidationStateChanged = { [weak self] in
            // Animate height changes smoothly
            self?.tableView.beginUpdates()
            self?.tableView.endUpdates()
        }
        
        return cell
    }
}

Key Notes: #

• We trim whitespace from text field inputs to ensure empty spaces don't count as valid content.
• The onValidationStateChanged closure keeps the cell decoupled from the table view while enabling height updates.
• Using beginUpdates() and endUpdates() ensures the table view recalculates the cell's height with a smooth animation.

内容的提问来源于stack exchange，提问作者Ho Si Tuan