[iOS]UITextField和UITextView限制输入字符数量方面
demo:http://download.csdn.net/download/u012881779/9960401
UITextField和UITextView限制输入字符数量，以前一直是在对应的代理方法（shouldChangeCharactersInRange:）中操作。但这样操作存在一个bug（如图），在将要超过限制时输入一串比较长的字符串，选择这段字符串时就会提示“超过限制”，实际上这时是还能继续输入几个字符的。
本文主要就是为了解决这类bug。
#import "DMViewController.h" // 限制输入字符数 #define YH_LIMITWORD 20 #define YH_LIMITTEXTWORD 60 @interface DMViewController () <UITextViewDelegate> @property (weak, nonatomic) IBOutlet UITextField *titleText; @property (weak, nonatomic) IBOutlet UITextView *contentTextView; @property (strong, nonatomic) NSString *defaultText; @end @implementation DMViewController - (void)dealloc { [[NSNotificationCenter defaultCenter] removeObserver:self]; } - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event { [self.view endEditing:YES]; } - (void)viewDidLoad { [super viewDidLoad]; _defaultText = @"限制输入60个字符"; // 方式一 [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textDidChangeAction:) name:@"UITextFieldTextDidChangeNotification" object:_titleText]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textDidChangeAction:) name:@"UITextViewTextDidChangeNotification" object:_contentTextView]; // 方式二（UITextField可以在UIControlEventEditingChanged事件的响应textDidChangeAction方法） // [_titleText addTarget:self action:@selector(textDidChangeAction:) forControlEvents:UIControlEventEditingChanged]; // 方式三（UITextView可以在代理方法textViewDidChange中调用textDidChangeAction方法） } #pragma mark - Notification - (void)textDidChangeAction:(NSNotification *)sender { UITextField *textObject; if ([[sender class] isSubclassOfClass:[NSNotification class]]) { textObject = sender.object; } else { textObject = (id)sender; } NSInteger limitNum; if ([[textObject class] isSubclassOfClass:[UITextField class]]) { limitNum = YH_LIMITWORD; } else { limitNum = YH_LIMITTEXTWORD; } NSString *toBeString = textObject.text; // 获取高亮部分 UITextRange *selectedRange = [textObject markedTextRange]; UITextPosition *position = [textObject positionFromPosition:selectedRange.start offset:0]; // 没有高亮选择的字，则对已输入的文字进行字数统计和限制 if (!position) { if (toBeString.length > limitNum) { NSRange rangeIndex = [toBeString rangeOfComposedCharacterSequenceAtIndex:limitNum]; if (rangeIndex.length == 1) { textObject.text = [toBeString substringToIndex:limitNum]; } else { NSRange rangeRange = [toBeString rangeOfComposedCharacterSequencesForRange:NSMakeRange(0, limitNum)]; textObject.text = [toBeString substringWithRange:rangeRange]; } } } } #pragma mark - UITextViewDelegate - (BOOL)textViewShouldBeginEditing:(UITextView *)textView { NSString *text = textView.text; if ([text containsString:_defaultText]) { text = [text stringByReplacingOccurrencesOfString:_defaultText withString:@""]; } textView.text = text; return YES; } - (void)textViewDidEndEditing:(UITextView *)textView { if ([textView.text isEqualToString:@""]) { textView.text = _defaultText; } } - (void)textViewDidChange:(UITextView *)textView { //[self textDidChangeAction:(id)textView]; } @end示意图：
