AFNetworking实现程序重新启动时的断点续传
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- //获取已下载的文件大小
- - (unsigned long long)fileSizeForPath:(NSString *)path {
- signed long long fileSize = 0;
- NSFileManager *fileManager = [NSFileManager new]; // default is not thread safe
- if ([fileManager fileExistsAtPath:path]) {
- NSError *error = nil;
- NSDictionary *fileDict = [fileManager attributesOfItemAtPath:path error:&error];
- if (!error && fileDict) {
- fileSize = [fileDict fileSize];
- }
- }
- return fileSize;
- }
- //开始下载
- - (void)startDownload {
- NSString *downloadUrl = @"http://www.xxx.com/xxx.zip";
- NSString *cacheDirectory = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0];
- NSString *downloadPath = [cacheDirectory stringByAppendingPathComponent:@"xxx.zip"];
- NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:downloadUrl]];
- //检查文件是否已经下载了一部分
- unsigned long long downloadedBytes = 0;
- if ([[NSFileManager defaultManager] fileExistsAtPath:downloadPath]) {
- //获取已下载的文件长度
- downloadedBytes = [self fileSizeForPath:downloadPath];
- if (downloadedBytes > 0) {
- NSMutableURLRequest *mutableURLRequest = [request mutableCopy];
- NSString *requestRange = [NSString stringWithFormat:@"bytes=%llu-", downloadedBytes];
- [mutableURLRequest setValue:requestRange forHTTPHeaderField:@"Range"];
- request = mutableURLRequest;
- }
- }
- //不使用缓存,避免断点续传出现问题
- [[NSURLCache sharedURLCache] removeCachedResponseForRequest:request];
- //下载请求
- AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
- //下载路径
- operation.outputStream = [NSOutputStream outputStreamToFileAtPath:downloadPath append:YES];
- //下载进度回调
- [operation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead) {
- //下载进度
- float progress = ((float)totalBytesRead + downloadedBytes) / (totalBytesExpectedToRead + downloadedBytes);
- }];
- //成功和失败回调
- [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
- } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
- }];
- [operation start];
- }
需要注意的是,此种写法仅适用于下载zip包,因为下载其他格式的文件有可能出现数据过多的情况。当文件已经下载完成时,再次调用该函数,无法判断文件是否已经下载完整,于是会再次下载,此时服务器会报416错,同时返回也会输出到文件中,使得文件大小异常。但是zip格式不受影响。
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