检察网络连接是否可用(使用官网上的reachability代码)

检查网络连接是否可用(使用官网上的reachability代码)

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] setNetworkStatusNotificati*****Enabled: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 didReceiveResp*****e:(NSURLResp*****e *)resp*****e;           - (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 didReceiveResp*****e:(NSURLResp*****e *)resp*****e {         // 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 {            /* appends the new data to the received 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];