iOS 按字节数截取及(普通length截取)字符串-NSString

显示的效果是：我们是一个快乐的...(超过一定(例子是8个)数量时，后面的用...代替)

1.第一种情况字符串的截取。

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//1.字符串设置长度，长度限制----字符串（目的：超过length时，后面显示...代码如下） + (NSString *)stringWithHtml:(NSString *)str length:(CGFloat)length{     if (!str) return nil;     if (str  && [str isKindOfClass:[NSString class]]) {         CGFloat  character = 0;         const char *chars = [str cStringUsingEncoding:NSUTF8StringEncoding];         NSUInteger charLength = length;         if (strlen(chars) <= charLength*3 +1) {//1个汉字或中文字符3个字节，1个英文1个字节（NSUTF8StringEncoding只适用于这个方法）             return str;         } //如果有宽度限制的话，建议用 if(str.length<=length){return str}; //缺点是字母或数字或中文与数字字母混合时计算有误，还会执行下面方法，但比较保险         //获取字数(字节数乘以2即可)         for(int i=0; i< [str length];i++){             int a = [str characterAtIndex:i];             if( a >= 0x4e00 && a <= 0x9fa5){ //判断是否为中文                 character +=1;             }else{                 if ((isalpha(a))||(isalnum(a))||isascii(a)) {                     character+=0.5;                 }else{                     character +=1;                 }             }             if (character > length) {//按字数截取                 if (character == length) {                       str = [str substringToIndex:i+1];                 }else{                      str = [str substringToIndex:i];                 }                 str = [str stringByAppendingString:@"..."];                 break;             }         }     }     return str; }

2.第二种情况简单富文本的截取。

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//2.NSAttributedString 按照字符数(中文1个字占1位)量截取 + (NSAttributedString*)subString:(NSAttributedString*)str len:(NSInteger)len{     if (!str) return nil;     if (str.length <=len) return str;     NSUInteger count = 0;     NSMutableAttributedString *sb = [[NSMutableAttributedString alloc]init];     for (int i = 0; i< str.length; i++) {         NSRange range = NSMakeRange(i, 1) ;         NSAttributedString *aStr = [str attributedSubstringFromRange:range];         count += [aStr.string lengthOfBytesUsingEncoding:NSUTF8StringEncoding]>1?2:1;         [sb appendAttributedString:aStr];         if(count >= len*2) {//因为上面已经返回1或2了所以这里乘以2             if (i == str.length -1) {                 return sb;             }else{                 if (sb) {                     NSMutableAttributedString *temp1 = [[NSMutableAttributedString alloc]initWithAttributedString:sb];                     [temp1 appendAttributedString:[[NSAttributedString alloc] initWithString:@"..."]];                     return temp1;                 }             }         }     }     return str; }

3.第三种情况不管是富文本还是字符串规定用length来判断长度并截取。

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NSString *subTitle = @"服务器返回的富文本或字符串"     if (subTitle) {         NSAttributedString *attribute = [CommonUtil attributedStringWithHtml:subTitle];         if (attribute && [attribute length] > 8) {             NSMutableAttributedString *muAttribute = [[NSMutableAttributedString alloc] initWithAttributedString:attribute];             [muAttribute replaceCharactersInRange:NSMakeRange(8,[attribute length]-8) withString:@"..."];             _subLabel.attributedText = muAttribute;         }else{             _subLabel.attributedText = attribute;         }     }