iPhone网络开发

一：确认网络环境3G/WIFI

    1. 添加源文件和framework
    
    开发Web等网络应用程序的时候，需要确认网络环境，连接情况等信息。如果没有处理它们，是不会通过Apple的审查的。
    Apple 的 例程 Reachability 中介绍了取得/检测网络状态的方法。要在应用程序程序中使用Reachability，首先要完成如下两部：
    
    1.1. 添加源文件：
    在你的程序中使用 Reachability 只须将该例程中的 Reachability.h 和 Reachability.m 拷贝到你的工程中。如下图：
    
    1.2.添加framework：
    将SystemConfiguration.framework 添加进工程。如下图：
    
    
    2. 网络状态
    
    Reachability.h中定义了三种网络状态：
typedef enum { NotReachable = 0, //无连接 ReachableViaWiFi, //使用3G/GPRS网络 ReachableViaWWAN //使用WiFi网络 } NetworkStatus;

 
    
    因此可以这样检查网络状态：

    

Reachability *r = [Reachability reachabilityWithHostName:@“www.apple.com”]; switch ([r currentReachabilityStatus]) { case NotReachable: // 没有网络连接 break; case ReachableViaWWAN: // 使用3G网络 break; case ReachableViaWiFi: // 使用WiFi网络 break; }

     
    3.检查当前网络环境

 

 

    程序启动时，如果想检测可用的网络环境，可以像这样
    

// 是否wifi + (BOOL) IsEnableWIFI { return ([[Reachability reachabilityForLocalWiFi] currentReachabilityStatus] != NotReachable); } // 是否3G + (BOOL) IsEnable3G { return ([[Reachability reachabilityForInternetConnection] currentReachabilityStatus] != NotReachable); }

    

例子：

- (void)viewWillAppear:(BOOL)animated { if (([Reachability reachabilityForInternetConnection].currentReachabilityStatus == NotReachable) && ([Reachability reachabilityForLocalWiFi].currentReachabilityStatus == NotReachable)) { self.navigationItem.hidesBackButton = YES; [self.navigationItem setLeftBarButtonItem:nil animated:NO]; } }

 
    4. 链接状态的实时通知

    网络连接状态的实时检查，通知在网络应用中也是十分必要的。接续状态发生变化时，需要及时地通知用户：
    
    Reachability 1.5版本
    // My.AppDelegate.h

 

 #import "Reachability.h"

 @interface MyAppDelegate : NSObject <UIApplicationDelegate> {
     NetworkStatus remoteHostStatus;
 }

 @property NetworkStatus remoteHostStatus;

 @end

 // My.AppDelegate.m
 #import "MyAppDelegate.h"

 @implementation MyAppDelegate
 @synthesize remoteHostStatus;

 // 更新网络状态
 - (void)updateStatus {
     self.remoteHostStatus = [[Reachability sharedReachability] remoteHostStatus];
 }

 // 通知网络状态
 - (void)reachabilityChanged:(NSNotification *)note {
     [self updateStatus];
     if (self.remoteHostStatus == NotReachable) {
         UIAlertView *alert = [[UIAlertView alloc] initWithTitle:NSLocalizedString(@"AppName", nil)
                      message:NSLocalizedString (@"NotReachable", nil)
                     delegate:nil cancelButtonTitle:@"OK" otherButtonTitles: nil];
         [alert show];
         [alert release];
     }
 }

 // 程序启动器，启动网络监视
 - (void)applicationDidFinishLaunching:(UIApplication *)application {

     // 设置网络检测的站点
     [[Reachability sharedReachability] setHostName:@"www.apple.com"];
     [[Reachability sharedReachability] setNetworkStatusNotificationsEnabled:YES];
     // 设置网络状态变化时的通知函数
     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityChanged:)
                                              name:@"kNetworkReachabilityChangedNotification" object:nil];
     [self updateStatus];
 }

 - (void)dealloc {
     // 删除通知对象
     [[NSNotificationCenter defaultCenter] removeObserver:self];
     [window release];
     [super dealloc];
 }

 
    
    Reachability 2.0版本
    

    // MyAppDelegate.h
   

 @class Reachability;
 @interface MyAppDelegate : NSObject <UIApplicationDelegate> {
             Reachability  *hostReach;
         }

 @end

     // MyAppDelegate.m
  - (void)reachabilityChanged:(NSNotification *)note {
         Reachability* curReach = [note object];
         NSParameterAssert([curReach isKindOfClass: [Reachability class]]);
         NetworkStatus status = [curReach currentReachabilityStatus];

         if (status == NotReachable) {
             UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"AppName""
                               message:@"NotReachable"
                               delegate:nil
                               cancelButtonTitle:@"YES" otherButtonTitles:nil];
                               [alert show];
                               [alert release];
         }
     }

     - (void)applicationDidFinishLaunching:(UIApplication *)application {
         // ...

         // 监测网络情况
         [[NSNotificationCenter defaultCenter] addObserver:self
                               selector:@selector(reachabilityChanged:)
                               name: kReachabilityChangedNotification
                               object: nil];
         hostReach = [[Reachability reachabilityWithHostName:@"www.google.com"] retain];
         hostReach startNotifer];
         // ...
     }

 

二：使用NSConnection下载数据
    
    1.创建NSConnection对象，设置委托对象
    

 NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:[self urlString]]];
 [NSURLConnection connectionWithRequest:request delegate:self];

 
    
    2. NSURLConnection delegate委托方法
      

 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response;
       - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error;
       - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data;
       - (void)connectionDidFinishLoading:(NSURLConnection *)connection;

 
    3. 实现委托方法
  

 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
       // store data
       [self.receivedData setLength:0];            //通常在这里先清空接受数据的缓存
   }

   - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {

       [self.receivedData appendData:data];        //可能多次收到数据，把新的数据添加在现有数据最后
   }

   - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
       // 错误处理
   }

   - (void)connectionDidFinishLoading:(NSURLConnection *)connection {
       // disconnect
       [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
       NSString *returnString = [[NSString alloc] initWithData:self.receivedData encoding:NSUTF8StringEncoding];
       NSLog(returnString);
       [self urlLoaded:[self urlString] data:self.receivedData];
       firstTimeDownloaded = YES;
   }

 
三：使用NSXMLParser解析xml文件

    1. 设置委托对象，开始解析

 NSXMLParser *parser = [[NSXMLParser alloc] initWithData:data];   //或者也可以使用initWithContentsOfURL直接下载文件，但是有一个原因不这么做：
     // It's also possible to have NSXMLParser download the data, by passing it a URL, but this is not desirable
     // because it gives less control over the network, particularly in responding to connection errors.
     [parser setDelegate:self];
     [parser parse];

 

    2. 常用的委托方法
    

 - (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName
                                 namespaceURI:(NSString *)namespaceURI
                                 qualifiedName:(NSString *)qName
                                 attributes:(NSDictionary *)attributeDict;
     - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName
                                 namespaceURI:(NSString *)namespaceURI
                                 qualifiedName:(NSString *)qName;
     - (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string;
     - (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError;

     static NSString *feedURLString = @"http://www.yifeiyang.net/test/test.xml";

 
    3.  应用举例
   

 - (void)parseXMLFileAtURL:(NSURL *)URL parseError:(NSError **)error
    {
        NSXMLParser *parser = [[NSXMLParser alloc] initWithContentsOfURL:URL];
        [parser setDelegate:self];
        [parser setShouldProcessNamespaces:NO];
        [parser setShouldReportNamespacePrefixes:NO];
        [parser setShouldResolveExternalEntities:NO];
        [parser parse];
        NSError *parseError = [parser parserError];
        if (parseError && error) {
            *error = parseError;
        }
        [parser release];
    }

    - (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI
                                        qualifiedName:(NSString*)qName attributes:(NSDictionary *)attributeDict{
        // 元素开始句柄
        if (qName) {
            elementName = qName;
        }
        if ([elementName isEqualToString:@"user"]) {
            // 输出属性值
            NSLog(@"Name is %@ , Age is %@", [attributeDict objectForKey:@"name"], [attributeDict objectForKey:@"age"]);
        }
    }

    - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI
                                        qualifiedName:(NSString *)qName
    {
        // 元素终了句柄
        if (qName) {
               elementName = qName;
        }
    }

    - (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
    {
        // 取得元素的text
    }

    NSError *parseError = nil;
    [self parseXMLFileAtURL:[NSURL URLWithString:feedURLString] parseError:&parseError];