iOS WebView使用Ajax与iOS的交互

iOS 使用Ajax实现与Javascript同步异步交互

实现原理：

1.Ajax可以实现同步与异步请求
2.UIWebView可以实现Ajax跨域请求
3.NSURLProtocol可以拦截Ajax请求
4.NSURLProtocol可以实现模拟响应结果

需要解决的问题：

1.实现NSURLProtocol拦截Ajax请求

2.实现Ajax跨域，解决Ajax预检请求问题

3.实现NSURLProtocol返回响应

对于上述问题，我们定义自己的NSURLProtocol

#import <Foundation/Foundation.h>

@interface MyURLProtocol : NSURLProtocol


@end

代码实现

我们这里指定schema为 oschina://

对于其中可能遇到预检请求问题，请参阅（Ajax跨域(CROS)请求中的Preflighted Requests）

@interface MyURLProtocol()
 @property(nomatic,strong) NSMutableDictionary * reponseHeader;
@end

@implementation MyURLProtocol

//复写canInitWithRequest，决定是否拦截请求
+(BOOL)canInitWithRequest:(NSURLRequest *)request{

   //这里实现对  oschina://syncHttpRequest和oschina://asyncHttpRequest拦截
    if(request.URL.scheme!=nil && [[request.URL.scheme lowercaseString] isEqualToString:@"oschina"])
    {

        if([request.URL.host isEqualToString:@"syncHttpRequest"] || [request.URL.host isEqualToString:@"asyncHttpRequest"])
        {
            if(_reponseHeader==nil)
             {
                 _reponseHeader = @{
                                  @"Access-Control-Allow-Credentials":@"true",
                                  @"Access-Control-Allow-Origin":@"*",
                                  @"Access-Control-Expose-Headers":@"jsStr",
                                  @"Access-Control-Allow-Methods":@"GET,POST,PUT,OPTIONS,HEAD",
                                  @"Access-Control-Allow-Headers":@"Origin,jsStr,Content-Type,X-Request-Width",
                                  @"Access-Control-Max-Age":@"10",
                                  @"Cache-Control":@"no-cache,private",
                                  @"Pragma":@"no-cache,no-store",
                                  @"Expires":@"0",
                                  @"Connection":@"Close"
                                  };
            }
            return YES;
        }
   }
    //如果不拦截，则返回NO
    return NO;
}

//复写 canonicalRequestForRequest ,加工请求，这里我们可以不加工，直接使用req
+ (NSURLRequest*) canonicalRequestForRequest:(NSURLRequest *)req
{

    return req;
}
//复写startLoading,并处理预检请求
- (void) startLoading{
    //处理跨域操作,如果是options操作。如果是跨域访问会发送一个options请求，需要response一个权限才会继续走head请求
  //此外，ajax发送的数据无法被接收，需要一个自定义请求头X-Javascript-Header，用来javascript->iOS传递数据
  if ([self.request.HTTPMethod isEqualToString:@"OPTIONS"])
    {

        NSDictionary * fields_resp = _reponseHeader;
        //响应ajax预检请求
        NSHTTPURLResponse *response = [[NSHTTPURLResponse alloc] initWithURL:[self.request URL] statusCode:200 HTTPVersion:@"1.1" headerFields:fields_resp];
        [[self client] URLProtocol: self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
        [[self client] URLProtocol:self didLoadData:[NSData data]];
        [[self client] URLProtocolDidFinishLoading:self];
    }else{
        //实现对ajax正式请求的解析与响应
        [self doRequestToResponse];
    }

}

-(void) doRequestToResponse
{

    NSDictionary *dic = [self.request.allHTTPHeaderFields copy];
    NSString *jsStr = dic[@"X-Javascript-Header"];  //获取响应头数据
    NSString * userAgentInStorage   = [[NSUserDefaults standardUserDefaults] stringForKey:@"UserAgent"];
    NSString * userAgent =  dic[@"User-Agent"];


//必要时保存user-Agent
    if([NSString isEmptyOrNil:userAgentInStorage] && ![NSString isEmptyOrNil:userAgent])
    {
        [[NSUserDefaults standardUserDefaults] setObject:userAgent forKey:@"UserAgent"];
        [[NSUserDefaults standardUserDefaults] synchronize];

    }
   if([NSString isEmptyOrNil:jsStr])
    {
        [self sendRequestErrorToClient];
        return;
    }

  if([jsStr hasPrefix:@"@"])
    {
        jsStr = [jsStr stringByReplacingOccurrencesOfString:@"@" withString:@""];
    }

    NSData *data = [GTMBase64 decodeString:jsStr];
    jsStr = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

    // 转换
    jsStr = [jsStr stringByReplacingOccurrencesOfString:@"\n" withString:@"\\n"];
    jsStr = [jsStr stringByReplacingOccurrencesOfString:@"\r" withString:@"\\r"];
    jsStr = [jsStr stringByReplacingOccurrencesOfString:@"\t" withString:@"\\t"];
    jsStr = [jsStr stringByReplacingOccurrencesOfString:@"\0" withString:@"\\0"];


    NSMutableDictionary *jsDic = [jsStr mutableObjectFromJSONString];

    if(jsDic==nil)
    {
        NSString * tempJsStr = [jsStr stringByReplacingOccurrencesOfString:@"\\" withString:@"\\\\"];
        jsDic = [tempJsStr mutableObjectFromJSONString];
    }
    if(jsDic==nil)
    {
        [UMJS showToast:@"参数解析失败！"];
        return;
    }

    NSString *serviceName= jsDic[@"service"];
    NSString *methodName = jsDic[@"method"];
    id params = jsDic["params"];

   [------------------处理响应的请结果------------------------]
     //1.开始处理，略
    //发送相应数据到Ajax端,假定结果为result
   NSString * response = [@{@"result":result,@"msg":@"Hello World",@"code":@1} JSONString];
  [self sendResponseToClient:response];
   [------------------处理响应的请结果------------------------]

}

-(void) sendResponseToClient:(NSString *) str
{
     NSData *repData = [str dataUsingEncoding:NSUTF8StringEncoding];


    NSMutableDictionary *respHeader = [NSMutableDictionary dictionaryWithDictionary:fields_resp];
    respHeader[@"Content-Length"] = [NSString stringWithFormat:@"%ld",repData.length];

    NSHTTPURLResponse *response = [[NSHTTPURLResponse alloc] initWithURL:[self.request URL] statusCode:200 HTTPVersion:@"1.1" headerFields:respHeader];

    [[self client] URLProtocol: self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
    [[self client] URLProtocol:self didLoadData:repData];
    [[self client] URLProtocolDidFinishLoading:self];

 }



//发送错误请求信息
-(void) sendRequestErrorToClient
{

    NSData *data = [@"" dataUsingEncoding:NSUTF8StringEncoding];
    NSDictionary * fields_resp =_reponseHeader;
    NSHTTPURLResponse *response = [[NSHTTPURLResponse alloc] initWithURL:[self.request URL] statusCode:400 HTTPVersion:@"1.1" headerFields:fields_resp];
    [[self client] URLProtocol: self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
    [[self client] URLProtocol:self didLoadData:data];
    [[self client] URLProtocolDidFinishLoading:self];

}

- (void) stopLoading{
//    NSLog(@"stopLoading");
}
//处理跳转
(NSURLRequest *)connection:(NSURLConnection *)connection willSendRequest:(NSURLRequest *)request redirectResponse:(NSURLResponse *)response { 
if ([response isKindOfClass:[NSHTTPURLResponse class]]) 
{ 
NSHTTPURLResponse *HTTPResponse = (NSHTTPURLResponse *)response;
 if ([HTTPResponse statusCode] == 301 || [HTTPResponse statusCode] == 302) 
{ 
NSMutableURLRequest *mutableRequest = [request mutableCopy]; 
[mutableRequest setURL:[NSURL URLWithString:[[HTTPResponse allHeaderFields] objectForKey:@”Location”]]];
 request = [mutableRequest copy];
 [[self client] URLProtocol:self wasRedirectedToRequest:request redirectResponse:response]; 
} 
} 
return request; 
}

自定义结束之后，我们需要在AppDetegate或者UIViewController注册一下才行，注意：多次注册也是可以的，不会造成多次拦截。

[NSURLProtocol registerClass:[UyURLProtocol class]];

通过这种方式，我们可以实现iOS端数据处理，在Javascript端我们需要实现2类调用，同步和异步

//异步请求
function sendAsyncAjax(xJavascript, onload, onerror) {

     var xhr, results, url;
     url = 'oschina://asyncHttpRequest?rnd='+Math.random();
     xhr = new XMLHttpRequest();
   try{

     xhr.open('POST', url, true);
     xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
     xhr.setRequestHeader("Cache-Control", "no-cache,private");
     xhr.setRequestHeader("Pragma", "no-cache,no-store");
     xhr.setRequestHeader("User-Agent", navigator.userAgent);
    //通过X-Javascript-Header发送数据到iOS,注意，使用第三方Base64 encode
    xhr.setRequestHeader("X-Javascript-Header", Base64Util.encode(xJavascript));

     xhr.onload = function (e) {
         if (this.status === 200) {
             results = JSON.parse(xhr.responseText);
             onload(results);
         }else{
             onload({'e':e});
         }
     };

     xhr.onerror = function (e) {
         onerror({'e':e});
     };

     }catch(exception){
       console.error(exception);

   }finally{
    try{
    xhr.send(null);
    }catch(exception2){}
  }
}

//同步请求
function sendSyncAjax(xJavascript) {

     var xhr, results, url;
     url = 'oschina://syncHttpRequest?rnd='+Math.random();
     xhr = new XMLHttpRequest();
   try{

     xhr.open('POST', url, true);
     xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
     xhr.setRequestHeader("Cache-Control", "no-cache,private");
     xhr.setRequestHeader("Pragma", "no-cache,no-store");
     xhr.setRequestHeader("User-Agent", navigator.userAgent);
     //通过X-Javascript-Header发送数据到iOS,注意，使用第三方Base64 encode
    xhr.setRequestHeader("X-Javascript-Header", Base64Util.encode(xJavascript));

     }catch(exception){
       console.error(exception);

     }finally{
    try{
      xhr.send(null);

    }catch(exception2){}
  }
 if (xhr.readyState == 4) {

        if (xhr.status == 200) {
           return  xhr.execXhr.responseText;
        } else {
            return xhr.execXhr.responseText;
        }
    }

 return {};
}

然后我们通过javascript调用

var script = JSON.stringify({service:"NetworkUtil",method:"getNetworkInfo",params:{}};
sendAsyncAjax(script ,function(result){

}, function(error){

});
或者
var script = JSON.stringify({service:"NetworkUtil",method:"getNetworkInfo",params:{}};
var result = sendSyncAjax(script);

一般来说NetworkUtil可以调用的方法必须是类方法

扫描二维码关注公众号，回复： 1753143 查看本文章

@implementation NetworkUtil

+(NSString * )getNetworkInfo

{

  NSString * result = [略];

  return result;

}

@end

我们这里实现了iOS平台上同步异步的方法，Android平台有系统提供的javascriptInterface接口，当然，我们想要实现和本篇iOS类似的方式，我们可以使用ServerSocket方式来实现，具体过程可能使用到信号量的概念，这里不再赘述.

大家可以加我的微信，我会提供关于iOS开发相关的各种资料！

文章转载于：
http://www.code4app.com/home.php
(出处: Code4App-iOS开发-iOS 开源代码库-iOS代码实例搜索-iOS特效示例-iOS代码例子下载-Code4App.com)