iOS乱码

有的二维码生成的含有中文的数据编码是GBK编码，如百度二维码生成器，使用系统原生二维码扫描就会出现乱码，于是开始网上查阅，该试的方法都尝试过了，终于功夫不负有心人，问题得到了解决，先上代码

<code class="hljs objectivec has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NSString</span> *result=<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.ScanResultString</span>;<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//返回的扫描结果</span>
        NSData *data=[<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.ScanResultString</span> dataUsingEncoding:NSUTF8StringEncoding];
        NSStringEncoding enc = CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingGB_18030_2000);
        <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NSString</span> *retStr = [[<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NSString</span> alloc] initWithData:data encoding:enc];<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//如果中文是utf-8编码转gbk结果为空(还没搞明白)</span>
   <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (retStr)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//如果扫描中文乱码则需要处理，否则不处理</span>
     {
       <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NSInteger</span> max = [<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.ScanResultString</span> length]；
       <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">char</span> *nbytes = malloc(max + <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>);
       <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i < max; i++)
       {
          <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">unichar</span> ch = [<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.ScanResultString</span>  characterAtIndex: i];
          nbytes[i] = (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">char</span>) ch;
       }
       nbytes[max] = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'\0'</span>;
      result=[<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NSString</span> stringWithCString: nbytes
                                      encoding: enc];

</code><code class="hljs objectivec has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">
</code><code class="hljs objectivec has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">
</code><code class="hljs objectivec has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">
</code><code class="hljs objectivec has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">
</code><code class="hljs objectivec has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">
</code><code class="hljs objectivec has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">
</code><code class="hljs objectivec has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">
</code><code class="hljs objectivec has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">
</code><code class="hljs objectivec has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">     }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li></ul>

这样处理后的结果就可以解决乱码问题了 
问题分析： 
比如使用百度二维码生成器生成一个纯文本二维码，内容是:二维码ok 
不处理，扫描的结果是:¶þάÂëok,乱码。。。。 
因为 NSString 本身是按照 UTF-16 编码的，所以如果逐个字符地观察这个错误解码后的 NSString:

int max = [str length]; 
int i; 
for (i = 0; i < max; i++) 
{ 
unichar ch = [str characterAtIndex: i]; 
printf(“%x “, ch); 
} 
我们可以得到:

b6 fe ce ac c2 eb 6f 6b  
这样一串输出，6f 6b 就是 ok，比较好认，前面的b6 fe ce ac c2 eb 是什么呢？一查，原来是“二维码”这三个字的 GBK 编码。

这就好理解了：NSString 一开始把一段 GBK 编码的字节流逐个字节地按照 8bit处理了，原本 8 个字节对应的是 5 个字符，结果被错误地解码为了 8 个字符，所以我们要把它转换回去，首先是要还原回原来的那段字节流:

int max = [str length]; 
char *nbytes = malloc(max + 1);

int i; 
for (i = 0; i < max; i++) 
{ 
unichar ch = [str characterAtIndex: i]; 
nbytes = (char) ch; 
} 
nbytes = ‘\0’; 
然后再将这段字节流按照正确的编码 (GB18030) 处理:

NSStringEncoding enc = CFStringConvertEncodingToNSStringEncoding( 
kCFStringEncodingGB_18030_2000);

NSLog(@”处理后: %@”, [NSString stringWithCString: nbytes 
encoding: enc]); 
结果果然得到了正确的输出