iOS 文件下载 （AFNetwork 三方框架 含progressView）五

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)totalBytesWrittentotalBytesExpectedToWrite:(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。

/** [""] *@briefThe 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 *)downloadTaskdidFinishDownloadingToURL:(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];}