ios网络开发 网络状态检查

网络连接中用到的类：

一.Reachability 

    1.添加 Reachability 的.h和.m文件，再添加SystemConfiguration.framework。

    2.Reachability中定义了三种网络状态：

  typedef Num{

NotReachable = 0,  //无连接

ReachableViaWiFi,  //使用3G/GPRS网络

ReachableViaWWAN   //使用WiFi网络

       }NetworkStatus;

     3.示例：

  Reachability *reachability = [Reachablity  reachabilityWithHostName:@"www.baidu.com"];

  switch([reachabilityStatus]){

case  NotReachable:

//TODO 

break; 

case  ReachableViaWiFi:

//TODO  

break; 

case  ReachableViaWWAN:

//TODO  

break;  

 } 

      4.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，可以像这样来使用

  //是否wifi

+ (BOOL)isEnableWIFI 

{

return ([[Reachability reachabiliyForLocalWIFI] currentReachabilityStatus] != NotReachable); 

  }

   //是否3G

+ (BOOL)isEnable3G

{

return ([[Reachability reachabiliyForInternetConnetion] currentReachabilityStatus] != NotReachable); 

   }

   示例：

- (void)viewWillAppear:(BOOL)animated

{ 

  if (([Reachability reachabiliyForInternetConnetion].currentReachabilityStatus == NotReachable) && [Reachability                         reachabiliyForLocalWIFI].currentReachabilityStatus == NotReachable))

{

self.navigationItem.hidesBackButton = YES;

[self.navigationItem setLeftBarButtonItem:nil animated:NO]; 

} 

 } 

       5.链接状态的实时通知

实时检查，持续状态发生变化时，需要及时地通知用户：

Reachability 1.5版本
//MyAppDelegate.h

#import "Reachability"

@interface MyAppDelegate:NSObject<UIApplicationDelegate>
{
    
}

@property NetworkStatus remoteHostStatus;

@end 

 //MyAppDelegate.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)
   {
       UIAlert *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
{
   //设置网络监测的站点
   [[Reachability sharedReachability] setHostName:@"www.baidu.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

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


@end 
 
 //MyAppDelegate.m

#import "MyAppDelegate.h"

@implementation MyAppDelegate

//通知网络状态
- (void)reachabilityChanged:(NSNotification *)note
{
    Reachability *currentReach = [note object];
    NSParameterAssert([currentReach isKindOfClass:[Reachability class]]);
    NetworkStatus status = [currentReach currentReachabilityStatus]; 

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

   [alert show];
   [alert release];
    }
}


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

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


}

二、其他常用的类。

 1.NSURL

 2.NSURLRequest

 3.NSMutableURLRequest 是NSURLRequest的子类，可以设置一些请求参数

 4.NSURLResponse 

 5.NSError