UITextView 200字符限制，中文算1个字，英文算0.5个字

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//注册监听方法

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textViewChanged:) name:UITextViewTextDidChangeNotification object:self.replyTextView];

/**
* 计算输入的字数,超出规定字数不允许输入

* @param noti 通知

- (void)textViewChanged:(NSNotification *)noti
{
    NSString * textContent = self.replyTextView.text;
    int existTextNum = [textContent lengthForCString];;

    NSString *language = [self.replyTextView.textInputMode primaryLanguage];

    if ([language isEqualToString:@"zh-Hans"]) {
        //中文
        UITextRange * selectedRange = [self.replyTextView markedTextRange];
        UITextPosition * position = [self.replyTextView positionFromPosition:selectedRange.start offset:0];

        if (!position) {
            //没有选中字符

            if (existTextNum > TextViewMaxLength) {
                //大于200字符
                textContent = [textContent subStringWithByteLength:TextViewMaxLength];
                existTextNum = TextViewMaxLength;
                self.replyTextView.text = textContent;
            }else
            {
                //小于200字符
//                existTextNum = [textContent lengthForCString];
            }
        }else
        {
            //有选中字符
//            existTextNum = [textContent lengthForCString];
        }
    }else
    {
        //英文

// existTextNum = [textContent lengthForCString];

if (existTextNum > TextViewMaxLength)

{

//大于200字符

textContent = [textContent subStringWithByteLength:TextViewMaxLength];

existTextNum = TextViewMaxLength;

self.replyTextView.text = textContent;

}

    }

    self.currentCountLabel.text = [NSString stringWithFormat:@"%d", existTextNum];

}

//下面这两个个都是分类里的方法，写个NSString的分类放里面用就可以了。

//这个方法从网上找的。

/**
*  计算字符串字节长度,中文一个字节，英文0.5字节
*
*  @return 字节长度
*/
- (int)lengthForCString
{
    int strlength = 0;
    char * p = (char *)[self cStringUsingEncoding:NSUnicodeStringEncoding];
    for (int i = 0; i < [self lengthOfBytesUsingEncoding:NSUnicodeStringEncoding]; i ++) {
//        NSLog(@"*p:%c",*p);
        if (* p) {
            p ++;
            strlength ++;
        }
        else {
            p ++;
        }
    }
    return (strlength + 1)/2;

}

//这个是自己写的。

/**
*  按字节数截取字符串，中文一个字节，英文0.5字节，如果最后字符是半个中文，自动抛掉最后一个字符
*
*  @param length 字节数
*
*  @return 截取后的字符串
*/
- (NSString *)subStringWithByteLength:(int)length
{
    float bytesCount = 0;
    float lastBytesCount = 0;
    for (int i = 1; i <= self.length; i ++) {

        //        NSLog(@"byteLength:%ld", [[self substringWithRange:NSMakeRange(i - 1, 1)] lengthOfBytesUsingEncoding:NSUTF8StringEncoding]);

        if ([[self substringWithRange:NSMakeRange(i - 1, 1)] lengthOfBytesUsingEncoding:NSUTF8StringEncoding] == 3) {
            bytesCount ++;
        }else
        {
            bytesCount += 0.5;
        }

        if (bytesCount > length) {
            //            NSLog(@"byteCount:%f", lastBytesCount);
            return [self substringWithRange:NSMakeRange(0, i - 1)];
        }else if (bytesCount == length)
        {
            return [self substringWithRange:NSMakeRange(0, i)];
        }else
        {
            lastBytesCount = bytesCount;
        }
    }
    return @"按字节截取字符串出错，请检查截取字节是否超出范围。";

}

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