ios – 仅在输入后启用UIAlertController的UIAlertAction

@property(nonatomic,strong)UIAlertAction *okAction;

然后在ViewController的viewDidLoad方法中复制以下代码

self.okAction = [UIAlertAction actionWithtitle:@"OK"
                                         style:UIAlertActionStyleDefault
                                       handler:nil];
self.okAction.enabled = NO;

UIAlertController *controller = [UIAlertController alertControllerWithtitle:nil
                                                                    message:@"Enter your text"
                                                             preferredStyle:UIAlertControllerStyleAlert];

[controller addTextFieldWithConfigurationHandler:^(UITextField *textField) {

    textField.delegate = self;
}];

[controller addAction:self.okAction];
[self presentViewController:controller animated:YES completion:nil];

还要在类中实现以下UITextField委托方法

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRangE)range replacementString:(NSString *)String{

    NSString *finalString = [textField.text StringByreplacingCharactersInRange:range withString:string];
   [self.okAction setEnabled:(finalString.length >= 5)];
   return YES;
}

这应该工作