AFNetworking进行数据获取

最新推荐文章于 2024-02-18 23:11:29 发布

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本文介绍通过URL获取不同类型的网络资源，包括JSON数据、图片及plist文件的方法。详细讲解了使用AFNetworking库进行异步请求的过程，并提供了具体的代码示例。

如何通过URL获取json数据
第一种，利用AFJSONRequestOperation，官方网站上给的例子：
NSString *str=[NSString stringWithFormat:@"https://alpha-api.app.net/stream/0/posts/stream/global"];
    NSURL *url = [NSURL URLWithString:[str stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    //    从URL获取json数据
    AFJSONRequestOperation *operation1 = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, NSDictionary* JSON) {
                NSLog(@"获取到的数据为：%@",JSON);
    } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id data) {
        NSLog(@"发生错误！%@",error);
    }];
    [operation1 start];

 
第二种方法，利用AFHTTPRequestOperation 先获取到字符串形式的数据，然后转换成json格式，将NSString格式的数据转换成json数据，利用IOS5自带的json解析方法：
NSString *str=[NSString stringWithFormat:@"https://alpha-api.app.net/stream/0/posts/stream/global"];
    NSURL *url = [NSURL URLWithString:[str stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
   AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
    [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
        NSString *html = operation.responseString;
             NSData* data=[html dataUsingEncoding:NSUTF8StringEncoding];
             id dict=[NSJSONSerialization  JSONObjectWithData:data options:0 error:nil];
        NSLog(@"获取到的数据为：%@",dict);
    }failure:^(AFHTTPRequestOperation *operation, NSError *error) {
        NSLog(@"发生错误！%@",error);
    }];
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    [queue addOperation:operation];
如果发生Error Domain=NSURLErrorDomain Code=-1000 "bad URL" UserInfo=0x14defc80 {NSUnderlyingError=0x14deea10 "bad URL", NSLocalizedDescription=bad URL这个错误，请检查URL编码格式。有没有进行stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding
 
 
如何通过URL获取图片
异步获取图片，通过队列实现，而且图片会有缓存，在下次请求相同的链接时，系统会自动调用缓存，而不从网上请求数据。
UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0.0f, 100.0f, 100.0f, 100.0f)]; 
    [imageView setImageWithURL:[NSURL URLWithString:@"http://i.imgur.com/r4uwx.jpg"] placeholderImage:[UIImage imageNamed:@"placeholder-avatar"]]; 
    [self.view addSubview:imageView];

上面的方法是官方提供的，还有一种方法，
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.scott-sherwood.com/wp-content/uploads/2013/01/scene.png"]];
    AFImageRequestOperation *operation = [AFImageRequestOperation imageRequestOperationWithRequest:request imageProcessingBlock:nil success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
        self.backgroundImageView.image = image;
    } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) {
        NSLog(@"Error %@",error);
    }];
 
    [operation start];

 
如果使用第一种URLWithString：  placeholderImage：会有更多的细节处理，其实实现还是通过AFImageRequestOperation处理，可以点击URLWithString：  placeholderImage：方法进去看一下就一目了然了。所以我觉得还是用第一种好。
 
如何通过URL获取plist文件
通过url获取plist文件的内容，用的很少，这个方法在官方提供的方法里面没有
 NSString *weatherUrl = @"http://www.calinks.com.cn/buick/kls/Buickhousekeeper.plist";
    NSURL *url = [NSURL URLWithString:[weatherUrl stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    [AFPropertyListRequestOperation addAcceptableContentTypes:[NSSet setWithObject:@"text/plain"]];
    AFPropertyListRequestOperation *operation = [AFPropertyListRequestOperation propertyListRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id propertyList) {
        NSLog(@"%@",(NSDictionary *)propertyList);
        
    }failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id propertyList) {
        NSLog(@"%@",error);
    }];
 
    [operation start];

如果稍不留神，可能就出现Error Domain=AFNetworkingErrorDomain Code=-1016 "Expected content type {(
    "application/x-plist"
)}, got text/plain" UserInfo=0x16e91ce0 {NSLocalizedRecoverySuggestion=
 
...
...
, AFNetworkingOperationFailingURLRequestErrorKey= { }, NSErrorFailingURLKey=, NSLocalizedDescription=Expected content type {(
    "application/x-plist"
)}, got text/plain, AFNetworkingOperationFailinponseErrorKey= { URL:  } { status code: 200, headers {
    "Accept-Ranges" = bytes;
    Connection = "keep-alive";
    "Content-Length" = 974;
    "Content-Type" = "text/plain";
    Date = "Sat, 25 Jan 2014 07:29:26 GMT";
    Etag = ""1014c2-3ce-4ee63e1c80e00"";
    "Last-Modified" = "Wed, 25 Dec 2013 23:04:24 GMT";
    Server = "nginx/1.4.2";
 
} }}
可能还会出现乱码，解决办法就是[AFPropertyListRequestOperation addAcceptableContentTypes:[NSSet setWithObject:@"text/plain"]];