网络,json,xml
通过NSURLConnection实现网络数据下载 通过NSURLConnection这个类来创建一个异步的请求 NSURLconnection提供了两种方式来实现链接,一种是同步的,另一种是异步的。异步的链接将会创建一个新的线程,这个线程将会来负责下载的动作。同步的链接将会堵塞当前线程,也就是说会造成当前的主线程堵塞,直到这个同步的线程运行完毕将会继续运行主线程。 同步和异步的主要区别就是运行的时候是否会创建一个新的现成,异步的会穿啊构建一个新的,而同步的并不会。 为了能够创建一个异步的请求连接,我们需要做如下操作: 1.创建一个NSString类型的URL链接字符串 2.把NSString类型转化成网络可识别的NSURL类型。 3.把我们的URL对象赋值到NSURLRequest对象中,如果是多个连接请求,请使用NSMutableURLRequest。 4.创建一个NSURLConnection的链接实例,然后把我们定义好的URL对象赋值过去。 我们可以创建一个异步的URL连接对象通过 sendAsynchronousRequest:queue:completionHandler 这个方法 这个方法参数如下: sendAsynchronousRequest 一个NSURLRequest类型请求。 Queue 一个操作队列,wo我们可以很轻松的分配和初始化一个操作队列,然后可以根据我们需求添加到这个方法的参数中。 completionHandler 一个临时堵塞的监听不获取,当我们异步链接的操作完成之后,无论我们的异步操作是否成功,这个对象都能够接到如下三个参数: 1.一个NSURLResopne,这个对象是服务器返回给我们的数据包装对象。2.NSData,可选的,这个是我们通过URL请求返回的数据。3.NSError类型的对象,如果请求中有错误发生。 这个sendAsynchronousRequest:queue:completionHandler方法如果是添加在主线程上的将不会被调用,因此如果你想执行一个跟UI相关的任务,那么你的主线程就会被堵塞。
NSString *urlAsString = @"http://www.apple.com"; NSURL *url = [NSURL URLWithString:urlAsString]; NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url]; NSOperationQueue *queue = [[NSOperationQueue alloc]init]; [NSURLConnection sendAsynchronousRequest: urlRequest queue:queue completionHandler:^( NSURLResponse *response, NSData *data, NSError *error ){ if([data length>0] && error == nil){ NSString *html = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding]; NSLog(@"HTML = %@",html); }else if([data length] == 0 && error == nil){ NSLog(@"Nothing was downloaded."); }else if(error != nil){ NSLog(@"Error happened = %@",error); } }]; 如果你想保存从网络上下载的数据到你的硬盘中,那么你要在完成的block中将使用NSData的适当方法。
NSString *urlAsString = @"http://www.apple.com"; NSURL *url = [NSURL URLWithString:urlAsString]; NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url]; NSOperationQueue *queue = [[NSOperationQueue alloc]init]; [NSURLConnection sendAsynchronousRequest: urlRequest queue:queue completionHandler:^( NSURLResponse *response, NSData *data, NSError *error ){ if([data length>0] && error == nil){ NSString * documentsDir= [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES)objectAtIndex:0]; NSString *filePath = [documentsDir stringByAppendingPathComponent:@"apple.html"]; [data writeToFile:filePath atomically:YES]; NSLog(@"Successfully saved the file to %@",filePath); }else if([data length] == 0 && error == nil){ NSLog(@"Nothing was downloaded."); }else if(error != nil){ NSLog(@"Error happened = %@",error); } }];
捕获异步链接中超时的问题 在创建一个URL请求对象并且准备传递给NSURLConnection,设置一下你的超时值。 NSString *urlAsString = @"http://www.apple.com"; NSURL *url = [NSURL URLWithString:urlAsString]; NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:30.0f]; NSOperationQueue *queue = [[NSOperationQueue alloc]init]; [NSURLConnection sendAsynchronousRequest: urlRequest queue:queue completionHandler:^( NSURLResponse *response, NSData *data, NSError *error ){ if([data length>0] && error == nil){ NSString *html = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding]; NSLog(@"HTML = %@",html); }else if([data length] == 0 && error == nil){ NSLog(@"Nothing was downloaded."); }else if(error != nil){ NSLog(@"Error happened = %@",error); } }]; 解析的时候超过了30秒,那么运行的时候这个访问对象将会给你一个超时的错误。
通过NSURLConnection创建一个同步的下载
通过NSURlConnection的sendSynchronousRequest:returningResponse:error:方法创建一个同步的网络连接。 在创建一个同步的网链接的时候我们需要明白一点,并不是我们的这个同步连接一定会堵塞我们的主线程,如果这个同步的链接是创建在主线程上的,那么这种情况下是会堵塞我们的主线程的。其他情况下是不一定会堵塞我们的主线程的。 这个例子中,我们将会尝试取回Yahoo主页的内容: -(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{ NSLog(@"We are here ... "); NSString *urlAsString = @"http://www.yahoo.com"; NSURL *url = [NSURL URLWithString:urlAsString]; NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url]; NSURLResponse *response = nil; NSError *error = nil; NSLog(@"Firing synchronous url connection..."); NSData *data = [NSURLConnection sendSynchronousRequest:urlRequest returningResponse:&response error:&error]; if([data length]>0 && error == nil){ NSLog(@"%lu bytes of data was returned.",(unsigned long)[data length]); }else if ([data length] == 0 && error == nil){ NSLog(@"No data was returned."); }else if (error != ni){ NSLog(@"Error happened = %@",error); NSLog(@"We are done."); } self.window = [[UIWindow alloc]initWithFrame:[[UIScreen mainScreen]bounds]]; self.window.backgroundColor = [UIColor whiteColor]; [self.window makeKeyAndVisible]; return YES; } 打印效果: We are here... -(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{ NSLog(@"We are here ... "); NSString *urlAsString = @"http://www.yahoo.com"; NSLog(@"Firing synchronous url connection...");
dispatch_queue_t dispatchQueue = dispatch_get_global_queue(DISPATCH_PRIORITY_DEFAULT, 0); dispatch_async(dispatchQueue, ^(void){ NSURL *url = [NSURL URLWithString:urlAsString]; NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url]; NSURLResponse *response = nil; NSError *error = nil; NSData *data = [NSURLConnection sendSynchronousRequest:urlRequest returningResponse:&response error:&error]; if([data length]>0 && error == nil){ NSLog(@"%lu bytes of data was returned.",(unsigned long)[data length]); }else if ([data length] == 0 && error == nil){ NSLog(@"No data was returned."); }else if (error != ni){ NSLog(@"Error happened = %@",error); } }); NSLog(@"We are done.");
self.window = [[UIWindow alloc]initWithFrame:[[UIScreen mainScreen]bounds]]; self.window.backgroundColor = [UIColor whiteColor]; [self.window makeKeyAndVisible]; return YES; } 打印效果: We are here... 看了如上的代码是不是感觉特别奇怪,怎么 we are done 还是放在最后面的,怎么现在打印到前面的了,这 就是我们要证明的,其实同步的程序并不一定会堵塞我们的主线程的。只要我们的这个同步的线程并不是建立 在我们的主线程上的,如果我们把他添加到 GCD 队列池中的话,那么我们的主线程也就没有被堵塞。这样同 步的概念实际上也可以看做是某种程度上的异步。 通过NSMutableURLRequest包装URL的请求形式 你想在传给一个请求链接前能适应一个URL的不同HTTP头及其设置。
通过NSMutableURLRequest代替NSURLRequest 通常我们的URL请求可能是一组,并不是一个,而且我们的URL请求也是会不停的根据流程在变化的,所以我们要仍然使用NSURLRequest这个对象是不能随时的进行一个URL的变化的,因此我们的NSmutableURLRequest这个对象,可以用来解决我们这个问题。 在分配和初始化了请求之后修改请求url的timeout: NSString *urlAsString = @"http://www.apple.com"; NSURL *url = [NSURL URLWithString:urlAsString]; NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; [urlRequest setTimeoutInterval:30.0f];
在分配和初始化了请求之后设置请求的URL和timeout: NSString *urlAsString = @"http://www.apple.com"; NSURL *url = [NSURL URLWithString:urlAsString]; NSMutableURLRequest *request = [NSMutableURLRequest new]; [urlRequest setTimeoutInterval:30.0f]; [urlRequest setURL:url];
通过NSURLConnection发送一个HTTP GET 请求 你想通过Http协议向服务器发送一个Get的包装请求,并在这个请求中添加了一些请求参数 NSString *urlAsString = @"http:///get.php"; urlAsString = [urlAsString stringByAppendingString:@"?param1 = First"]; urlAsString = [urlAsString stringByAppendingString:@"¶m2 = Second"]; NSURL *url = [NSURL URLWithString:urlAsString]; NSMutableURLRequest *urlRequest = [NSMutableURLRequest requestWithURL:url]; [urlRequest setTimeoutInterval:30.0f]; [urlRequest setHTTPMethod:@"GET"]; NSOperationQueue *queue = [[NSOperationQueue alloc]init]; [NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandle:^(NSURLResponse *response,NSData *data,NSError *error){ if([data length]>0 && error == nil){ NSString *html = [[NSString alloc]initWithData:data encoding:NSUTF8String]; NSLog(@"HTML = %@",html); }else if([data length] ==0 && error == nil ){ NSLog(@"Nothing was downloaded."); }else if(error != nil){ NSLog(@"Error happened = %@",error); } }];
编译效果: html = <html> <head> <title>IOS 5 Programming Cookbook GET Example</title> </head> <body> <b>HTTP Method</b>=GET<br>Query String</b> =Array([param1] =>First [param2]=>Second) </body> </html>
通过NSURLConnection发送一个POST表单请求 NSString *urlAsString = @"http:///get.php"; urlAsString = [urlAsString stringByAppendingString:@"?param1 = First"]; urlAsString = [urlAsString stringByAppendingString:@"¶m2 = Second"]; NSURL *url = [NSURL URLWithString:urlAsString]; NSMutableURLRequest *urlRequest = [NSMutableURLRequest requestWithURL:url]; [urlRequest setTimeoutInterval:30.0f]; [urlRequest setHTTPMethod:@"POST"]; NSString *body = @"bodyParam1 = BodyValue1&bodyParam2 = BodyValue2"; [urlRequest setHTTPBody:[body dataUsingEncoding:NSUTF8StringEncoding]]; NSOperationQueue *queue = [[NSOperationQueue alloc]init]; [NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandle:^(NSURLResponse *response,NSData *data,NSError *error){ if([data length]>0 && error == nil){ NSString *html = [[NSString alloc]initWithData:data encoding:NSUTF8String]; NSLog(@"HTML = %@",html); }else if([data length] ==0 && error == nil ){ NSLog(@"Nothing was downloaded."); }else if(error != nil){ NSLog(@"Error happened = %@",error); } }]; 编译效果: html = <html> <head> <title>IOS 5 Programming Cookbook POST Example</title> </head> <body> <b>HTTP Method</b>=POST<br>Query String</b> =Array([param1] =>First [param2]=>Second) <b>Body parameters</b> = Array([bodyParam1]=>BodyValue1 [bodyParam2]=>BodyValue2) </body> </html>
通过NSURLConnection发生HTTP DELETE 请求 通过HTTP协议向服务器发送一个删除资源的一个URL链接,同时你也可以给这个请求添加参数
将[urlRequest setHTTPMethod:@"POST"]; 改为[urlRequest setHTTPMethod:@"DELETE"];
通过NSURLConnection发送HTTP PUT请求 就像发送POST,GET,DELETE请求一样。将相应位置设置成PUT;
把Array和Dictionaries序列化成JSON对象 通过NSJSONSerialization这个类的dataWithJSONObject:options:error:方法来实现 NSMutableDictionary *dictionary = [[NSMutableDictionary alloc]init]; [dictionary setValue:@"Anthony" forKey:@"First Name"]; [dictionary setValue:@"Robbins" forKey:@"Last Name"]; [dictionary setValue:[NSNumber numberWithUnsignedInteger:51] forKey:@"Age"]; NSArray *arrayOfAnthonysChildren = [[NSArray alloc]initWithObjects:@"Anthony's Son 1",@"Anthony's Danghter 1",@"Anthony's Son 2",@"Anthony's Son 3",@"Anthony's Daughter 2",nil]; [dictionary setValue: arrayOfAnthonysChildren forKey:@"children"];
NSError *error = nil; NSData *jsonData = [NSJSONSerialization dataWithISONObject:dictionary options:NSJSONWritingPrettyPrinted error:&error]; if([jsonData length]>0 && error == nil){ NSLog(@"Successfully serializes the dictionary into data = %@,jsonData"); }else if([jsonData length] == 0 && error == nil){ NSLog(@"No data returned after serialization."); }else if(error != nil){ NSLog(@"An error happened = %@",error); } 运行结果: successfully serialized the dictionary into data. JSON String = { "Last Name" : "Robbins", "First Name" : "Anthony", "children" : [ "Anthony's Son 1", "Anthony's Daughter 1", "Anthony's Son 2", "Anthony's Son 3", "Anthony's Daughter 2" ], "Age" : 51 } 把json数据转化成Arrays 或者Dictionaries 希望把一个json数据解析出来放在数据或者字典里保存,通过NSJSONSerialization 这个类的 JSONObjectWithData:options:error:方法来实现 error = nil; id jsonObject = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingAllowFragments error:&error]; if(jsonObject != nil && error == nil){ NSLog(@"Successfully deserialized … "); if([jsonObject isKindOfClass:[NSDictionary class]]){ NSDictionary *deserializedDictionary = (NSDictionary *)jsonObject; NSLog(@"Dersialized JSON Dictionary = %@",deserializedDictionary); }else if([jsonObject isKindOfClass:[NSArray class]]){ NSArray *deserializedArray = (NSArray *)jsonObject; NSLog(@"Dersialized JSON Array =%@",deserializedArray); } } else if(error != nil){ NSLog(@"An error happened while deserializing the JSON data."); } |
|