Question

我正在尝试使用类似于Notes应用程序的Swift构建应用程序，但是当用户按下“+”按钮添加新笔记时我想要弹出警报 - 并且警报会提示用户输入名称。然后将该名称添加为基础表中的新行。到目前为止，我已经能够做到这一点，但每次我点击“+”符号，我添加到警报的按钮都会重新添加。换句话说，警报应该有一个“OK”＆amp;一个“取消”按钮。但是在第二次弹出警报时，有2个“OK”按钮和2个“取消”按钮，依此类推。我有什么想法可以解决这个问题？谢谢你的帮助！

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

@IBOutlet weak var table: UITableView!

var data:[String] = []

//create alert controller
var alert = UIAlertController(title: "Name", message: "Enter a name", preferredStyle: .alert)



override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    self.title = "Notes"

    //create "add" button
    let addButton = UIBarButtonItem(barButtonSystemItem: .add, target: self, action: #selector(addAlert))
    self.navigationItem.rightBarButtonItem = addButton
    //create edit button so we can delete rows
    self.navigationItem.leftBarButtonItem = editButtonItem
    load()

}

//function to add new note. This code is executed when the "Add" button is clicked

func addNote()
{
    //code to prevent being able to add rows while in edit mode
    if (table.isEditing) {
        return
    }

    let textField = self.alert.textFields![0] as UITextField
    let name:String = textField.text!
    data.insert(name, at: 0)
    let indexPath:IndexPath = IndexPath(row: 0, section: 0)
    table.insertRows(at: [indexPath], with: .automatic)
    save()
}

func addAlert()
{
    alert.addTextField(configurationHandler: { (textField) -> Void in
        textField.placeholder = "Enter Name"})
    self.present(alert, animated: true, completion: nil)
    //grab value from the text field and print when user clicks OK
    alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { (UIAlertAction) in
        let textField = self.alert.textFields![0] as UITextField
        print("Text Field: \(textField.text!)")
        self.addNote()
    }))
}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return data.count
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell:UITableViewCell = tableView.dequeueReusableCell(withIdentifier: "cell")!
    cell.textLabel?.text = data[indexPath.row]
    return cell
}

override func setEditing(_ editing: Bool, animated: Bool) {
    super.setEditing(editing, animated: animated)
    //puts table in edit mode
    table.setEditing(editing, animated: animated)
}

//function to delete rows from table
func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
    data.remove(at: indexPath.row)
    table.deleteRows(at: [indexPath], with: .fade)
    save()
}

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    self.performSegue(withIdentifier: "detail", sender: nil)


}

func save()
{
    UserDefaults.standard.set(data, forKey: "notes")
    UserDefaults.standard.synchronize()
}

func load()
{
    if let loadedData = UserDefaults.standard.value(forKey: "notes") as? [String]
    {
        data = loadedData
        table.reloadData()
    }
}

Answer 1

在显示提醒之前输入alert.addAction。在addAlert（）方法中尝试此代码

func addAlert()
{
 var alert = UIAlertController(title: "Name", message: "Enter a name", preferredStyle: .alert)
 alert.addTextField(configurationHandler: { (textField) -> Void in
        textField.placeholder = "Enter Name"})


    alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { (UIAlertAction) in
        let textField = self.alert.textFields![0] as UITextField
        print("Text Field: \(textField.text!)")
        self.addNote()
    }))

    self.present(alert, animated: true, completion: nil)

}

Answer 2

只有在添加动作（按钮）后才能显示警告。

 public static String encrypt(String originalPassword) throws Exception {
    String methodName = "encrypt -->";
    _logger.debug(methodName + Constants.CALLED);
    String encryptedString = null;
    try {
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
        SecretKey key = keyFactory.generateSecret(new PBEKeySpec(PASSWORD));
        Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");
        pbeCipher.init(Cipher.ENCRYPT_MODE, key, new PBEParameterSpec(SALT, 20));
        encryptedString = base64Encode(pbeCipher.doFinal(originalPassword.getBytes("UTF-8")));
        _logger.debug(methodName + "encrypted string " + encryptedString);
    }  catch (Exception e) {
        _logger.error(methodName + "Encryption failed due to: " + e.getMessage());
        throw new Exception("Failed to Encrypt String");
    }
    _logger.debug(methodName + Constants.END);
    return encryptedString;
}

public static String decrypt(String encryptedPassword) throws Exception {
        String methodName = "decrypt -->";
        _logger.debug(methodName + Constants.CALLED);
        String decryptedString = null;
        try {
            _logger.debug(methodName + " string to decrypt " + encryptedPassword);
            SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
            SecretKey key = keyFactory.generateSecret(new PBEKeySpec(PASSWORD));
            Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");
            pbeCipher.init(Cipher.DECRYPT_MODE, key, new PBEParameterSpec(SALT, 20));
            decryptedString = new String(pbeCipher.doFinal(base64Decode(encryptedPassword)), "UTF-8");
        } catch (Exception e) {
            _logger.error(methodName + "Decryption failed due to: " + e.getMessage());
            throw new Exception("Failed to Decrypt String");
        }
        _logger.debug(methodName + Constants.END);
        return decryptedString;
    }

为什么UIAlert上的按钮重复？

2 个答案: