Question

我正在尝试限制允许用户在UITextField内输入UIAlertView字符的字符数。

我在网上尝试了一些常见的答案。如下图所示：

  #define MAXLENGTH 10


- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    if ([textField.text length] > MAXLENGTH) {
        textField.text = [textField.text substringToIndex:MAXLENGTH-1];
        return NO;
    }
    return YES;
}

任何人都可以提供帮助吗？

Answer 1

.h文件

  @property (strong,nonatomic)  UITextField *alertText;

@interface LocationSearchViewController : UIViewController<UITextFieldDelegate>

.m文件

- (IBAction)butPostalCode:(id)sender {

UIAlertView *alrt=[[UIAlertView alloc]initWithTitle:@"" message:@"" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:@"OK", nil];
alrt.alertViewStyle = UIAlertViewStylePlainTextInput;
[[alrt textFieldAtIndex:0] setPlaceholder:@"Enter postal Code"];
alertText = [alrt textFieldAtIndex:0];
alertText.keyboardType = UIKeyboardTypeNumberPad;
alertText.delegate=self;
alrt.tag=100;
[alrt show];
}



-(BOOL) textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
if(yourtextfieldname.text.length >= 10 && range.length == 0) {
    return NO;

}
return YES;
}

<强>夫特

class LocationSearchViewController: UIViewController, UITextFieldDelegate {

 Var alertText:UITextField!
}

func butPostalCode(sender: AnyObject) {
var alrt: UIAlertView = UIAlertView(title: "", message: "", delegate: self, cancelButtonTitle: "Cancel", otherButtonTitles: "OK")
alrt.alertViewStyle = .PlainTextInput
alrt.textFieldAtIndex(0).placeholder = "Enter postal Code"
alertText = alrt.textFieldAtIndex(0)
alertText.keyboardType = .NumberPad
alertText.delegate = self
alrt.tag = 100
alrt.show()
}

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
if yourtextfieldname.text.length >= 10 && range.length == 0 {
    return false
}
return true
}

Answer 2

不幸的是，这是不允许的。您不能混淆UIAlertView的层次结构，因此您无法像UITextField的属性那样更改内容。

请参阅此link

具体地

UIAlertView类旨在按原样使用，不支持子类化。此类的视图层次结构是私有的，不得修改

修改

虽然您不应该像我上面所说的那样弄乱UIAlertView层次结构，但您实际上可以设置UITextField委托，但首先需要检索它。首先确保已在头文件（UITextFieldDelegate文件）中设置.h。

然后，在您创建UIAlertView并设置alertViewStyle: property后，我们就像
一样
// We create an instance of our UIAlertView UIAlertView *myAlert = [[UIAlertView alloc] initWithTitle:@"My Alert" message:nil delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:@"OK", nil]; // We set the alertViewStyle to a plain text input, so 1 textfield [myAlert setAlertViewStyle:UIAlertViewStylePlainTextInput]; // Then we retrieve that UITextField from the index 0 UITextField *plainTextField = [myAlert textFieldAtIndex:0]; // Now that we have retrieved the text field we can set the delegate on it/ // Probably best to give it a tag as well so we can identify it later. [plainTextField setDelegate:self]; [plainTextField setTag:1001];

我们设置了委托后，您应该输入您的方法，因为shouldChangeCharactersInRange:是UITextFieldDelegate方法。

-(BOOL) textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string { // Make sure that it is our textField that we are working on otherwise forget the whole thing. if([textField tag] == 1001) { if([textField text].length >= 10 && range.length == 0) { return NO; } } return YES; }

警告

由于从textFieldAtIndex:检索的文本字段是UIAlertView层次结构的一部分，Apple可能会将其归类为更改UIAlertView不允许的内容（参见第一部分）回答）以及在使用addSubview:时不使用UIAlertView的任何内容

Answer 3

试试这个：

#define MAXLENGTH 10

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    NSString *nextValue = [NSString stringWithFormat:@"%@%@", textField.text, string];
    if ([nextValue length] > MAXLENGTH) {
        UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Attention"
                                              message:@"You can't insert more than 10 characters"                          
                                              delegate:nil cancelButtonTitle:nil                          
                                              otherButtonTitles:@"Close", nil];        
        [alert show];            
        return NO;            
    }
    return YES;
}

如何限制UIAlertView UITextField中的字符输入

3 个答案: