防止解雇UIAlertController

Question

我增加了UITextField一个UIAlertController,这似乎为AlertView.在解雇之前UIAlertController,我想验证输入UITextField.基于验证,我想解雇UIAlertController或不解雇.但我不知道如何防止UIAlertController按下按钮时的解除动作.有没有人解决这个问题或任何想法从哪里开始？我去谷歌但没有运气:/谢谢!

Answer 1

你是对的:如果用户可以点击警报中的按钮,则警报将被取消.所以你想阻止用户点击按钮!这只是禁用UIAlertAction按钮的问题.如果禁用警报操作,则用户无法点击它以解除警报.

要使用文本字段验证结合这一点,使用文本字段的委托方法或操作方法(在当你创建的文本字段的配置处理器配置)启用/禁用适当地取决于什么文本有(或没有)已经进入UIAlertActions .

这是一个例子.我们创建了这样的文本字段:

alert.addTextFieldWithConfigurationHandler {
    (tf:UITextField!) in
    tf.addTarget(self, action: "textChanged:", forControlEvents: .EditingChanged)
}

我们有一个取消操作和一个OK操作,我们将OK操作带入了禁用的世界:

(alert.actions[1] as UIAlertAction).enabled = false

随后,除非文本字段中有一些实际文本,否则用户无法点击OK:

func textChanged(sender:AnyObject) {
    let tf = sender as UITextField
    var resp : UIResponder = tf
    while !(resp is UIAlertController) { resp = resp.nextResponder() }
    let alert = resp as UIAlertController
    (alert.actions[1] as UIAlertAction).enabled = (tf.text != "")
}

编辑这是上面代码的当前(Swift 3.0.1及更高版本)版本:

alert.addTextField { tf in
    tf.addTarget(self, action: #selector(self.textChanged), for: .editingChanged)
}

和

alert.actions[1].isEnabled = false

和

@objc func textChanged(_ sender: Any) {
    let tf = sender as! UITextField
    var resp : UIResponder! = tf
    while !(resp is UIAlertController) { resp = resp.next }
    let alert = resp as! UIAlertController
    alert.actions[1].isEnabled = (tf.text != "")
}

Answer 2

我已经简化了亚马的答案而没有观察层次遍历.这将把动作本身作为一个弱变量.这是一个完全有效的例子:

weak var actionToEnable : UIAlertAction?

func showAlert()
{
    let titleStr = "title"
    let messageStr = "message"

    let alert = UIAlertController(title: titleStr, message: messageStr, preferredStyle: UIAlertControllerStyle.Alert)

    let placeholderStr =  "placeholder"

    alert.addTextFieldWithConfigurationHandler({(textField: UITextField) in
        textField.placeholder = placeholderStr
        textField.addTarget(self, action: "textChanged:", forControlEvents: .EditingChanged)
    })

    let cancel = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Cancel, handler: { (_) -> Void in

    })

    let action = UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: { (_) -> Void in
        let textfield = alert.textFields!.first!

        //Do what you want with the textfield!
    })

    alert.addAction(cancel)
    alert.addAction(action)

    self.actionToEnable = action
    action.enabled = false
    self.presentViewController(alert, animated: true, completion: nil)
}

func textChanged(sender:UITextField) {
    self.actionToEnable?.enabled = (sender.text! == "Validation")
}

Answer 3

关于@Matt的回答,这就是我在Obj-C中做同样事情的方式

- (BOOL)textField: (UITextField*) textField shouldChangeCharactersInRange: (NSRange) range replacementString: (NSString*)string
{
    NSString *newString = [textField.text stringByReplacingCharactersInRange: range withString: string];

    // check string length
    NSInteger newLength = [newString length];
    BOOL okToChange = (newLength <= 16);    // don't allow names longer than this

    if (okToChange)
    {
        // Find our Ok button
        UIResponder *responder = textField;
        Class uiacClass = [UIAlertController class];
        while (![responder isKindOfClass: uiacClass])
        {
            responder = [responder nextResponder];
        }
        UIAlertController *alert = (UIAlertController*) responder;
        UIAlertAction *okAction  = [alert.actions objectAtIndex: 0];

        // Dis/enable Ok button based on same-name
        BOOL duplicateName = NO;
        // <check for duplicates, here>

        okAction.enabled = !duplicateName;
    }


    return (okToChange);
}

Answer 4

我意识到这是在 Objectiv-C 中，但它显示了主体。稍后我将使用 swift 版本更新它。

您也可以使用块作为目标来执行相同的操作。

向您添加一个属性，ViewController以便块（swift 的闭包）具有强引用

@property (strong, nonatomic) id textValidationBlock;

然后AlertViewController像这样创建：

UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"Title" message:@"Message" preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {

}];

   __weak typeof(self) weakSelf = self;
UIAlertAction *okAction = [UIAlertAction actionWithTitle:@"Ok" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
        [weakSelf doSomething];

}];
[alertController addAction:cancelAction];
[alertController addAction:okAction];
[alertController.actions lastObject].enabled = NO;
self.textValidationBlock = [^{
    UITextField *textField = [alertController.textFields firstObject];
    if (something) {
        alertController.message = @"Warning message";
        [alertController.actions lastObject].enabled = NO;
    } else if (somethingElse) {
        alertController.message = @"Another warning message";
        [alertController.actions lastObject].enabled = NO;
    } else {
        //Validation passed
        alertController.message = @"";
        [alertController.actions lastObject].enabled = YES;
    }

} copy];
[alertController addTextFieldWithConfigurationHandler:^(UITextField * _Nonnull textField) {
    textField.placeholder = @"placeholder here";
    [textField addTarget:weakSelf.textValidationBlock action:@selector(invoke) forControlEvents:UIControlEventEditingChanged];
}];
[self presentViewController:alertController animated:YES completion:nil];