在前面的文章：[iOS]在WebApp中怎样使用JS调用iOS的函数 中，提到了怎样使用JS通过改动URL调用iOS的内部函数。

当中会遇到一个问题，就是编码问题。比方通过URL调用弹窗，在里面写上内容：你好汪海。

那链接大概就是这种：http://xxx.com#ios?action=alert&param=你好汪海

可是在iOS中接收到的时候会出现中文的乱码：

http://xxx.com#ios?action=alert&param=%25E6%2596%2587%25E4

遇到这个问题主要是URL在转化中的编码问题。解决方式感谢这篇博文：iOS中的编码问题。

将转码函数封装：

// 将URL编码
- (NSString *)encodeToPercentEscapeString: (NSString *) input
{
    NSString *outputStr = (NSString *) CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,
                                            (CFStringRef)input,
                                            NULL,
                                            (CFStringRef)@"!*‘();:@&=+$,/?
%#[]",
                                            kCFStringEncodingUTF8));
    return outputStr;
}

// 将URL解码
- (NSString *)decodeFromPercentEscapeString: (NSString *) input
{
    NSMutableString *outputStr = [NSMutableString stringWithString:input];
    [outputStr replaceOccurrencesOfString:@"+"
                               withString:@" "
                                  options:NSLiteralSearch
                                    range:NSMakeRange(0, [outputStr length])];
    
    return [outputStr stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
}

演示一下上面的封装函数：

    NSString * testUrl = @"http://search.google.com?keywords=($# it‘s {a*123})00!*‘();:@&=+$,/?%#[]";
    NSLog(@"original: %@", testUrl);


    NSString * encodeStr = [self encodeToPercentEscapeString:testUrl];
    NSLog(@"encoded: %@", encodeStr);
    
    NSString * encodeStr2 = [testUrl stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    NSLog(@"encoded2:%@", encodeStr2);
    
    NSString * decodeStr = [self decodeFromPercentEscapeString:encodeStr];
    NSLog(@"decoded: %@", decodeStr);

结果例如以下：    

    >> original: http://search.google.com?

keywords=($# it‘s {a*123})00!*‘();:@&=+$,/?%#[]
    >> encoded:  http%3A%2F%2Fsearch.google.com%3Fkeywords%3D%28%24%23%20it%27s%20%7Ba%2A123%7D%2900%21%2A%27%28%29%3B%3A%40%26%3D%2B%24%2C%2F%3F%25%23%5B%5D
    >> encoded2: http://search.google.com?keywords=($%23%20it‘s%20%7Ba*123%7D)00!*‘();:@&=+$,/?

%25%23%5B%5D
    >> decoded:  http://search.google.com?keywords=($# it‘s {a*123})00!*‘();:@&=+$,/?

%#[]

演示一下自带的URL转码測试代码：

  NSString* string1 = @"https://www.cloudsafe.com/目录";
    
    NSString* string2 = [string1 stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    
    NSString* string3 = [string2 stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    
    NSString* string4 = [string2 stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    
    NSString* string5 = [string3 stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    
    NSString* string6 = [string4 stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    
    NSString* string7 = [string5 stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    
    
    NSLog(@"原始数据%@",string1);
    NSLog(@"一层编码%@",string2);
    NSLog(@"两层编码%@",string3);
    NSLog(@"一层编码的一层解码%@",string4);
    NSLog(@"两层编码的一层解码%@",string5);
    NSLog(@"一层编码的两层解码%@",string6);
    NSLog(@"两层编码的两层解码%@",string7);
    

打印结果：

2014-06-10 15:00:02.425 DareWayApp[7400:671651] 原始数据https://www.cloudsafe.com/目录

2014-06-10 15:00:02.426 DareWayApp[7400:671651] 一层编码https://www.cloudsafe.com/%E6%96%87%E4%BB%B6%E5%A4%B9

2014-06-10 15:00:02.427 DareWayApp[7400:671651] 两层编码https://www.cloudsafe.com/%25E6%2596%2587%25E4%25BB%25B6%25E5%25A4%25B9

2014-06-10 15:00:02.427 DareWayApp[7400:671651] 一层编码的一层解码https://www.cloudsafe.com/目录

2014-06-10 15:00:02.427 DareWayApp[7400:671651] 两层编码的一层解码https://www.cloudsafe.com/%E6%96%87%E4%BB%B6%E5%A4%B9

2014-06-10 15:00:02.427 DareWayApp[7400:671651] 一层编码的两层解码https://www.cloudsafe.com/目录

2014-06-10 15:00:02.427 DareWayApp[7400:671651] 两层编码的两层解码https://www.cloudsafe.com/目录

假设server用的是GBK编码，仅仅要把上面的UTF改成以下的encoding就能够了：

 NSStringEncoding gbkEncoding = CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingGB_18030_2000);
        urlString = [urlString stringByReplacingPercentEscapesUsingEncoding:gbkEncoding];