1、网络监测


    //根据主机名判断网络是否连接

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

    self.reach = reach;

    //注册网络监听通知

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityChanged) name:kReachabilityChangedNotification object:nil];

    //开启监听

    [reach startNotifier];

   //根据currentReachabilityStatus判断网络状态

NotReachable = 0, //没有网络
ReachableViaWiFi = 2, //不用花钱WIFI
ReachableViaWWAN = 1 //2G,3G,4G
- (void)dealloc {
    
    //把当前的对象所有通知删除
    [[NSNotificationCenter defaultCenter] removeObserver:self];

    //停止监听
    [self.reach stopNotifier];
}

2、异步网络请求

//1、创建URL，访问网络资源的唯一地址

    NSURL * url = [NSURL URLWithString:@"http://192.168.1.123/demo.json"];
//2、创建网络请求

    /*

     cachePolicy 缓存策略

     NSURLRequestUseProtocolCachePolicy = 0, //自动缓存策略

     NSURLRequestReloadIgnoringLocalCacheData = 1, //每次都请求网络，无论本地是否存在缓存

     NSURLRequestReturnCacheDataElseLoad = 2,//如果有缓存返回缓存，没有就加载网络

     NSURLRequestReturnCacheDataDontLoad = 3,//如果有缓存返回缓存，没有也不加载网络

     timeoutInterval 请求超时 默认超时时间是60 一般设置 10 - 20s     

     */    



    NSURLRequest * request = [NSURLRequest requestWithURL:url cachePolicy:0 timeoutInterval:15];
//3、建立连接
//sendAsynchronousRequest 建立异步网络连接

//queue  可以传主队列，或全局队列

//[NSOperationQueue mainQueue]   不用调到主队列直接更新

//[[NSOperationQueue alloc] init]  则需要调回主线程更新UI

[NSURLConnection sendAsynchronousRequest:request queue:[[NSOperationQueue alloc] init] completionHandler:^(NSURLResponse * _Nullable response, NSData * _Nullable data, NSError * _Nullable connectionError) {

    //response 服务器响应信息，一般下载时有用

    //data  服务器返回的数据

    //connectionError 网络请求错误

    

    //服务器与客户端是以二进制流通讯的

    

    NSLog(@"%@",data);

    

    [data writeToFile:@"/Users/dahuan/Desktop/test" atomically:YES];

    

    NSLog(@"%@",[NSThread currentThread]);

    

    if (connectionError) {

        

        NSLog(@"错误信息：%@",connectionError);

        

    } else {

        

        NSLog(@"响应信息：%@",response);

        

        NSString * string = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

        

        NSLog(@"%@",string);

        

        [self.webView loadHTMLString:string baseURL:nil];

    }



    [[NSOperationQueue mainQueue] addOperationWithBlock:^{

        //更新UI

    }];

}];

3、同步网络请求

    NSURL * url = [NSURL URLWithString:@"http://192.168.1.123/demo.json"];
    
    NSURLRequest * request = [NSURLRequest requestWithURL:url];
    
    //同步网络请求
    
    NSURLResponse * response = nil;
    NSError * error = nil;
    
    NSData * data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
    
    NSString * string = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

    NSLog(@"%@",string);
    NSLog(@"%@",response);

4、NSURLConnection代理方法

    self.data = [NSMutableData data];
    
    NSString * urlString = @"http://192.168.1.123/把悲伤留给自己.mp3";
    
    //NSString 中包含中文字符时转换为NSURL
    urlString = [urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    
    NSURL * url = [NSURL URLWithString:urlString];
    
    NSURLRequest * request = [NSURLRequest requestWithURL:url];
    
    NSURLConnection * connect = [NSURLConnection connectionWithRequest:request delegate:self];
    
    //开启网络连接
    [connect start];
//服务器返回响应信息1
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
        
    NSLog(@"%@",response);
    
}
//接受数据（多次调用）2
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    
    [self.data appendData:data];
    
    NSLog(@"%@",data);
    
}
//请求完成3
- (void)connectionDidFinishLoading:(NSURLConnection *)connection{
    
    [self.data writeToFile:@"/Users/dahuan/Desktop/aaaaa.mp3" atomically:YES];
    NSLog(@"网络请求完成");
    
 }