AFN文件下载

1.采用 AFURLSessionManager 作为管理类

2.调用 NSURLSessionDownloadTask 类中的方法，做为下载类

- (NSURLSessionDownloadTask *)downloadTaskWithRequest:(NSURLRequest *)request
                                             progress:(NSProgress * __autoreleasing *)progress
                                          destination:(NSURL * (^)(NSURL *targetPath, NSURLResponse *response))destination
                                    completionHandler:(void (^)(NSURLResponse *response, NSURL *filePath, NSError *error))completionHandler

3. NSURLSessionDownloadTask方法中

   [downloadTask resume];    //进行开始下载

   [downloadTask suspend];   //进行暂停下载

4.调用 NSURLSessionTaskState state;方法判断状态

typedef NS_ENUM(NSInteger, NSURLSessionTaskState) {

    NSURLSessionTaskStateRunning = 0,                     /* 任务是否正在运行 */

    NSURLSessionTaskStateSuspended = 1,                //是否停止

    NSURLSessionTaskStateCanceling = 2,                   /* 是否取消*/

    NSURLSessionTaskStateCompleted = 3,                   /* 是否完成*/

}

 

示例：

- (Coding_DownloadTask *)addDownloadTaskForFile:(ProjectFile *)file completionHandler:(void (^)(NSURLResponse *response, NSURL *filePath, NSError *error))completionHandler{
    
    __weak typeof(file) weakFile = file;
    NSProgress *progress;
    
    NSURL *downloadURL = [NSURL URLWithString:file.downloadPath];
    NSURLRequest *request = [NSURLRequest requestWithURL:downloadURL];
    NSURLSessionDownloadTask *downloadTask = [self.af_manager downloadTaskWithRequest:request progress:&progress destination:^NSURL *(NSURL *targetPath, NSURLResponse *response)
    {
        NSURL *downloadUrl = [[Coding_FileManager sharedManager] urlForDownloadFolder];
        Coding_DownloadTask *cDownloadTask = [[Coding_FileManager sharedManager] cDownloadTaskForResponse:response];
        if (cDownloadTask) {
            downloadUrl = [downloadUrl URLByAppendingPathComponent:cDownloadTask.diskFileName];
        }else{
            downloadUrl = [downloadUrl URLByAppendingPathComponent:[response suggestedFilename]];
        }
        NSLog(@"download_destinationPath------\n%@", downloadUrl.absoluteString);
        return downloadUrl;
    } completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error) {
        if (error) {
            [[Coding_FileManager sharedManager] removeCDownloadTaskForKey:weakFile.storage_key];
        }else{
            [[Coding_FileManager sharedManager] removeCDownloadTaskForResponse:response];
        }
        if (completionHandler) {
            completionHandler(response, filePath, error);
        }
    }];
    
    Coding_DownloadTask *cDownloadTask = [Coding_DownloadTask cDownloadTaskWithTask:downloadTask progress:progress fileName:file.diskFileName];
    [self.downloadDict setObject:cDownloadTask forKey:file.storage_key];
    
    [downloadTask resume];
    return cDownloadTask;
}