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ios网络编程详解

wyy 2018年06月24日 手机开发 399 0
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 { 
           /* 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];


使用NSOperation和NSOperationQueue启动多线程
在app store中的很多应用程序非常的笨重,他们有好的界面,但操作性很差,比如说当程序从网上或本地载入数据的时候,界面被冻结了,用户只能等程序完全载入数据之后才能进行操作。 
当 打开一个应用程序时,iphone会产生一个包含main方法的线程,所用程序中的界面都是运行在这个线程之中的(table views, tab bars, alerts…),有时候我们会用数据填充这些view,现在问        题是如何有效的载入数据,并且用户还能自如的操作程序。方法是启动新的线 程,专门用于数据的下载,而主线程不会因为下载数据被阻塞。 
不管使用任何编程语言,在实现多线程时都是一件很麻烦的事情。更糟糕的是,一旦出 错,这种错误通常相当糟糕。然而,幸运的是apple从os x10.5在这方面做了很多的改进,NSThread的引入,使得开发多线程应用程序容易多了。除此之外,它们还引入了两个全新的 类,NSOperation和NSOperationQueue。 
接下来我们通过一个实例来剖析如何使用这两个类实现多线程。这里指示展示这两个类的基本用法,当然这不是使用他们的唯一办法。 
如 果你熟悉java或者它的别的变种语言的话 ,你会发现NSOperation对象很像java.lang.Runnable接口,就像java.lang.Runnable接口那 样,NSOperation类也被设计为可扩展的,而且只有一个需要重写的方法。它就是-(void)main。使用NSOperation的最简单的方 式就是把一个NSOperation对象加入到NSOperationQueue队列中,一旦这个对象被加入到队列,队列就开始处理这个对象,直到这个对 象的所有操作完成。然后它被队列释放。 
下面的例子中,使用一个获取网页,并对其解析程NSXMLDocument,最后将解析得到的NSXMLDocument返回给主线程。 
     
[email protected] PageLoadOperation : NSOperation { 
    NSURL *targetURL;} 
@property(retain) NSURL *targetURL; 
- (id)initWithURL:(NSURL*)url;@end 
 
PageLoadOperation.m 
#import "PageLoadOperation.h"#import "AppDelegate.h"@implementation [email protected] targetURL;- (id)initWithURL:(NSURL*)url;{ 
    if (![super init]) return nil; 
    [self setTargetURL:url]; 
    return self;}- (void)dealloc { 
    [targetURL release], targetURL = nil; 
    [super dealloc]; 

- (void)main  

    NSString *webpageString = [[[NSString alloc] 
    initWithContentsOfURL:[self targetURL]] autorelease]; 
    NSError *error = nil; 
    NSXMLDocument *document = [[NSXMLDocument alloc] 
    initWithXMLString:webpageString  
    options:NSXMLDocumentTidyHTML error:&error]; 
    if (!document) { 
        NSLog(@"%s Error loading document (%@): %@",  
        _cmd, [[self targetURL] absoluteString], error); 
         return; 
    } 
    [[AppDelegate shared] 
    performSelectorOnMainThread:@selector(pageLoaded:) 
         withObject:document waitUntilDone:YES]; 
    [document release]; 

@end 
    正 如我们所看到的那样,这个类相当的简单,在它的init方法中接受一个url并保存起来,当main函数被调用的时候,它使用这个保存的url创建一个字 符串,并将这个字符串传递给NSXMLDocumentinit方法。如果加载的xml数据没有出错,数据会被传递给AppDelegate,它处于主线 程中。到此,这个线程的任务就完成了。在主线程中注销操作队列的时候,会将这个NSOperation对象释放。 
AppDelegate.h 
@interface AppDelegate : NSObject { 
    NSOperationQueue *queue; 
}+ (id)shared;- (void)pageLoaded:(NSXMLDocument*)document;@endAppDelegate.m        #import "AppDelegate.h"#import "PageLoadOperation.h"@implementation AppDelegate 
static AppDelegate *shared; 
static NSArray *urlArray; 
- (id)init 

    if (shared) 
    { 
        [self autorelease]; 
        return shared; 
    } 
    if (![super init]) return nil;    NSMutableArray *array = [[NSMutableArray alloc] init];[array addObject:@"http://www.google.com"];[array addObject:@"http://www.apple.com"];[array addObject:@"http://www.yahoo.com"];[array addObject:@"http://www.zarrastudios.com"];[array addObject:@"http://www.macosxhints.com"];urlArray = array;    queue = [[NSOperationQueue alloc] init];shared = self;return self; 
    } 
    •    (void)applicationDidFinishLaunching: 
    (NSNotification *)aNotification 

        for (NSString *urlString in urlArray)  
        { 
        NSURL *url =  
        [NSURL URLWithString:urlString];        PageLoadOperation *plo =  
        [[PageLoadOperation alloc] initWithURL:url]; 
        [queue addOperation:plo]; 
        [plo release]; 
        } 

- (void)dealloc 

        [queue release], queue = nil; 
        [super dealloc]; 

+ (id)shared; 

        if (!shared) { 
            [[AppDelegate alloc] init]; 
        } 
        return shared; 

- (void)pageLoaded:(NSXMLDocument*)document; 

        NSLog(@"%s Do something with the XMLDocument: %@", 
             _cmd, document); 

@end 
 
NSOperationQueue的并行控制(NSOperationQueue Concurrency) 
        在 上面这个简单的例子中,我们很难看出这些操作是并行运行的,然而,如果你你的操作花费的时间远远比这里的要长,你将会发现,队列是同时执行这些操作的。幸 运的是,如果你想要为队列限制同时只能运行几个操作,你可以使用NSOperationQueue的 setMaxConcurrentOperationCount:方法。例如,[queue setMaxConcurrentOperationCount:2];
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