iOS 文件下载 （AFNetwork 三方框架 含progressView）五_afnetwork下载附件tableview

1.创建request

- (void)download2
{
    
    NSString *urlString = @"http:192.168.0.179:8080/Myweb/download.do";
    urlString = [urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
      NSLog(@"hello");
    NSURL *url = [NSURL URLWithString:urlString];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    [[self.session downloadTaskWithRequest:request] resume];
    
 
}

最后一句

[[self.session downloadTaskWithRequest:request] resume];

的session，本文使用懒加载

2. session懒加载，并添加代理，监听文件下载情况

// 懒加载
- (NSURLSession *)session
{
    if(_session == nil)
    {
        NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
        
        _session = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:nil];
        
    }
    return _session;
}

3.进度更新和label下载完成百分比更新（注意，一定要在主线程更新，不然无法显示）

/* Sent periodically to notify the delegate of download progress. */
/**
[""] *	@brief	更新进度条，使用此代理
[""] *
[""] *	@param 	session 	session
[""] *	@param 	downloadTask 	下载任务
[""] *	@param 	bytesWritten 	当前写入bytes
[""] *	@param 	totalBytesWritten 	当前总共写入bytes
[""] *	@param 	totalBytesExpectedToWrite 	期望写入的总bytes
[""] *
[""] *	@return	<#return value description#>
[""] */
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
      didWriteData:(int64_t)bytesWritten
 totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite
{
 
    float progress = (float)totalBytesWritten / totalBytesExpectedToWrite;
    NSLog(@"%f", progress);
    //主线程更新UI
    dispatch_async(dispatch_get_main_queue(), ^(void){
        self.progressLabel.text=[NSString stringWithFormat:@"%%%.0f",progress*100];
             [self.progressView setProgress:progress animated:YES];
    });
       
 
   
}

4. 下载完成，将下载的数据写入指定缓存路径。

/**
 [""] *	@brief	The delegate should copy or move the file at the given location to a new location as it will be
                removed when the delegate message returns.
[""] *
[""] *	@param 	session 	session description
[""] *	@param 	downloadTask 	downloadTask 下载任务
[""] *	@param 	location 	下载文档位置（临时）
[""] *
[""] *	@return
[""] */
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location
 
{
    NSString *cacheDir = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES)[0];
    
    NSString *retStr = [downloadTask.response.suggestedFilename stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    NSLog(@"%@ \n",retStr);
    
    NSString *path = [cacheDir stringByAppendingPathComponent:retStr];
    NSLog(@"%@",path);
    //NSURL *url2=location;
     NSLog(@"%@",location);
    NSData *mydata=[NSData dataWithContentsOfURL:location];
    [mydata writeToFile:path atomically:YES];
 
}