你的位置:首页 > 操作系统

[操作系统]NSURLSession下载和断点续传


  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 *)downloadTask   didWriteData:(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;  }) ;}