ios开发之UITextField、UITextView限制最大输入数

UITextField

不多说直接上代码

首先定一个全局常量maxNum, 指定一个最大输入范围

NSInteger const maxNum = 20;

创建一个UITextField对像，为你的UITextField对象添加监听方法

 [self.textField addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];

实现TextField的监听方法

#pragma mark -------UITextFiledDelegate

-(void)textFieldDidChange:(UITextField *)textField
{
    NSString *toBeString = textField.text;

    //获取高亮部分
    UITextRange *selectedRange = [textField markedTextRange];
    UITextPosition *position = [textField positionFromPosition:selectedRange.start offset:0];
    if (!position || !selectedRange)
    {
        if (toBeString.length > maxNum)
        {
            NSRange rangeIndex = [toBeString rangeOfComposedCharacterSequenceAtIndex:maxNum];
            if (rangeIndex.length == 1)
            {
                textField.text = [toBeString substringToIndex:maxNum];
            }
            else
            {
                NSRange rangeRange = [toBeString rangeOfComposedCharacterSequencesForRange:NSMakeRange(0, maxNum)];
                textField.text = [toBeString substringWithRange:rangeRange];
            }
        }
    }
}

UITextView

首定以一个全局常量

NSInteger const maxNum = 20;

创建一个UITextView对象并实现它的监听代理方法

#pragma mark ------- UITextViewDelegate

- (void)textViewDidChange:(UITextView *)textView
{
    if (textView.text.length >= maxDetailNum) {
        textView.text = [textView.text substringToIndex:maxDetailNum];
    }
}