iOS小知识点(四)网络篇

最新推荐文章于 2024-12-15 20:17:34 发布

原创最新推荐文章于 2024-12-15 20:17:34 发布 · 609 阅读

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CC 4.0 BY-SA版权

本文详细介绍如何在iPhone应用中实现网络状态检测、数据下载及XML解析等功能。包括使用Reachability类检查3G/WiFi网络连接状态，利用NSConnection进行数据下载，并通过NSXMLParser解析XML数据。

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网络编程总结 iphone

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(我们的)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 = [ReachabilityreachabilityWithHostName:@“ 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 ([[ReachabilityreachabilityForLocalWiFi] currentReachabilityStatus] != NotReachable);
    }

    // 是否3G
    + (BOOL) IsEnable3G {
        return ([[ReachabilityreachabilityForInternetConnection] currentReachabilityStatus] != NotReachable);
    }
例子：
    - (void)viewWillAppear:(BOOL)animated{
    if (([ReachabilityreachabilityForInternetConnection].currentReachabilityStatus == NotReachable)&&
           ([Reachability reachabilityForLocalWiFi].currentReachabilityStatus ==NotReachable)) {
            self.navigationItem.hidesBackButton= YES;
            [self.navigationItemsetLeftBarButtonItem: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 = [[ReachabilitysharedReachability] remoteHostStatus];
    }

    // 通知网络状态
    - (void)reachabilityChanged:(NSNotification*)note {
        [self updateStatus];
        if (self.remoteHostStatus ==NotReachable) {
            UIAlertView *alert = [[UIAlertViewalloc] initWithTitle:NSLocalizedString(@"AppName", nil)
                        message:NSLocalizedString (@"NotReachable", nil)
                        delegate:nilcancelButtonTitle:@"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([curReachisKindOfClass: [Reachability class]]);
        NetworkStatus status = [curReachcurrentReachabilityStatus];

        if (status == NotReachable) {
            UIAlertView *alert = [[UIAlertViewalloc] 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 = [[ReachabilityreachabilityWithHostName:@"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 = [NSMutableURLRequestrequestWithURL:[NSURL URLWithString:[self urlString]]];
    [NSURLConnectionconnectionWithRequest: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 {

        [self.receivedDataappendData: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
        [UIApplicati*****haredApplication].networkActivityIndicatorVisible = NO;
        NSString *returnString = [[NSStringalloc] 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 NSXMLParserdownload the data, by passing it a URL, but this is not desirable
    // because it gives less control over thenetwork, particularly in responding to connection errors.
    [parser setDelegate:self];
    [parser parse];

    2. 常用的委托方法
    - (void)parser:(NSXMLParser *)parserdidStartElement:(NSString *)elementName
                                namespaceURI:(NSString *)namespaceURI
                               qualifiedName:(NSString *)qName
                               attributes:(NSDictionary *)attributeDict;
    - (void)parser:(NSXMLParser *)parserdidEndElement:(NSString *)elementName
                               namespaceURI:(NSString *)namespaceURI
                               qualifiedName:(NSString *)qName;
    - (void)parser:(NSXMLParser *)parserfoundCharacters:(NSString *)string;
    - (void)parser:(NSXMLParser *)parserparseErrorOccurred:(NSError *)parseError;

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

    3. 应用举例
    - (void)parseXMLFileAtURL:(NSURL *)URLparseError:(NSError **)error
    {
        NSXMLParser *parser = [[NSXMLParseralloc] initWithContentsOfURL:URL];
        [parser setDelegate:self];
        [parser setShouldProcessNamespaces:NO];
        [parsersetShouldReportNamespacePrefixes:NO];
        [parsersetShouldResolveExternalEntities:NO];
        [parser parse];
        NSError *parseError = [parserparserError];
        if (parseError && error) {
            *error = parseError;
        }
        [parser release];
    }

    - (void)parser:(NSXMLParser *)parserdidStartElement:(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"], [attributeDictobjectForKey:@"age"]);
        }
    }

    - (void)parser:(NSXMLParser *)parserdidEndElement:(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:[NSURLURLWithString:feedURLString] parseError:&parseError];