UITextField限制字數的方法 .

 

在輸入東西的時候，如果想限制最大字數，可以用下面方法

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1. - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string;  
2. {  
3.     if ([string isEqualToString:@"\n"])   
4.     {  
5.         return YES;  
6.     }  
7.     NSString * toBeString = [textField.text stringByReplacingCharactersInRange:range withString:string];  
8.       
9.     if (self.myTextField == textField)   
10.     {  
11.         if ([toBeString length] > 20) {  
12.             textField.text = [toBeString substringToIndex:20];  
13.             UIAlertView *alert = [[[UIAlertView alloc] initWithTitle:nil message:@"超過最大字數不能輸入了" delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles:nil, nil] autorelease];  
14.             [alert show];  
15.             return NO;  
16.         }  
17.     }  
18.     return YES;  
19. }  

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string;{if ([string isEqualToString:@"\n"]) {return YES;}NSString * toBeString = [textField.text stringByReplacingCharactersInRange:range withString:string];if (self.myTextField == textField) {if ([toBeString length] > 20) {textField.text = [toBeString substringToIndex:20];UIAlertView *alert = [[[UIAlertView alloc] initWithTitle:nil message:@"超過最大字數不能輸入了" delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles:nil, nil] autorelease];[alert show];return NO;}} return YES;}