NSURLSession是iOS7之后新的网络接口，和经常用到NSURLConnection是类似的。在程序在前台时，，NSURLSession与NSURLConnection可以相互的替代。但是当用户在对程序进行强制关闭的时候此时NSURLSession会默认的自动断开。相比而言NSURLSession的优势主要体现在后台操作时候，而且在最流行的框架AFNetworking中也对NSURLSession提供了更好的支持。
主要提供的功能如下：
1 下载文件到内存中
2 下载文件到路径
3 上传制定的文件等
案例演示：图片下载断点续传
主要代码：
1、定义几个全局变量
@interface ViewController (){NSURLSessionDownloadTask * _task;NSData * _data;NSURLSession * _session;NSURLRequest * _request;UIProgressView * _pro;UIImageView * _imageView;}
2、向视图中添加图片进度条
_imageView=[[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 300, 300)];_imageView.center=self.view.center;[self.view addSubview:_imageView];_pro=[[UIProgressView alloc] initWithFrame:CGRectMake(_imageView.frame.origin.x, _imageView.frame.origin.y+400, 300, 40)];
3、向视图中添加按钮（同样的方式添加三个）
UIButton * button=[[UIButton alloc] initWithFrame:CGRectMake(50, _imageView.frame.origin.y+400+20, 50, 40)];button.backgroundColor=[UIColor blueColor];[button setTitle:@"开始" forState:UIControlStateNormal];[button addTarget:self action:@selector(ddLoad) forControlEvents:UIControlEventTouchUpInside];button.layer.borderWidth=1;button.layer.borderColor=[UIColor blueColor].CGColor;button.layer.cornerRadius=5;[self.view addSubview:button];
4、通过AFNetworkReachabilityManager网络状态监测
– (void) _checkNet{//开启网络状态监控[[AFNetworkReachabilityManager sharedManager] startMonitoring];[[AFNetworkReachabilityManager sharedManager] setReachabilityStatusChangeBlock:^(AFNetworkReachabilityStatus status) {if(status==AFNetworkReachabilityStatusReachableViaWiFi){NSLog(@"当前是wifi");}if(status==AFNetworkReachabilityStatusReachableViaWWAN){NSLog(@"当前是3G");}if(status==AFNetworkReachabilityStatusNotReachable){NSLog(@"当前是没有网络");}if(status==AFNetworkReachabilityStatusUnknown){NSLog(@"当前是未知网络");}}];}
5、开始下载
– (void) ddLoad{NSURLSessionConfiguration * config=[NSURLSessionConfiguration defaultSessionConfiguration];_session=[NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:nil];//NSURL *url=[NSURL URLWithString:@src];_request=[NSURLRequest requestWithURL:url];_task= [_session downloadTaskWithRequest:_request];NSLog(@"开始加载");[_task resume];}
6、设置暂停和回复
– (void) pause{//暂停NSLog(@"暂停下载");[_task cancelByProducingResumeData:^(NSData *resumeData) {_data=resumeData;}];_task=nil;}- (void) resume{//恢复NSLog(@"恢复下载");if(!_data){NSURL *url=[NSURL URLWithString:@src];_request=[NSURLRequest requestWithURL:url]；_task=[_session downloadTaskWithRequest:_request];}else{_task=[_session downloadTaskWithResumeData:_data];}[_task resume]; }
7、代理方法保存下载文件监控下载进度
#pragma mark – delegate- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location{NSURL * url=[NSURL fileURLWithPath:@"/Users/jredu/Desktop/tt.png"];NSFileManager * manager=[NSFileManager defaultManager];[manager moveItemAtURL:location toURL:url error:nil];dispatch_async(dispatch_get_main_queue(), ^{NSData * data=[manager contentsAtPath:@"/Users/jredu/Desktop/tt.png"];UIImage * image=[[UIImage alloc ]initWithData:data];_imageView.image=image;UIAlertView * alert=[[UIAlertView alloc] initWithTitle:nil message:@"下载完成" delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];[alert show];}) ;}- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTaskdidWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWrittentotalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite{CGFloat progress=(totalBytesWritten*1.0)/totalBytesExpectedToWrite;dispatch_async(dispatch_get_main_queue(), ^{_pro.progress=progress;}) ;}
看自家总在期待,不知将来好歹,新乐吧总在不断等待,
