AFNetworking實現程序從新啓動時的斷點續傳

今天須要用AFNetworking實現斷點續傳的功能，可是在進行了一番研究以後，發現AFNetworking雖然支持下載文件的暫停和繼續，可是程序從新啓動後再次下載沒法進行續傳。網上有說能夠經過AFDownloadRequestOperation這個AFNetworking的擴展庫來實現從新啓動後的續傳，可是通過本人測試，這個庫在最新的AFNetworking上會報錯，無奈之下，參考他的代碼，本身實現了一個，在這裏分享給你們。html

實現的代碼以下：緩存

 
   01. 
   //獲取已下載的文件大小 
  
   02. 
   - (unsigned long long)fileSizeForPath:(NSString *)path { 
  
   03. 
   signed long long fileSize = 0; 
  
   04. 
   NSFileManager *fileManager = [NSFileManager new]; // default is not thread safe 
  
   05. 
   if ([fileManager fileExistsAtPath:path]) { 
  
   06. 
   NSError *error = nil; 
  
   07. 
   NSDictionary *fileDict = [fileManager attributesOfItemAtPath:path error:&error]; 
  
   08. 
   if (!error && fileDict) { 
  
   09. 
   fileSize = [fileDict fileSize]; 
  
   10. 
   } 
  
   11. 
   } 
  
   12. 
   return fileSize; 
  
   13. 
   } 
  
   14. 
   //開始下載 
  
   15. 
   - (void)startDownload { 
  
   16. 
   NSString *downloadUrl = @"http://www.xxx.com/xxx.zip"; 
  
   17. 
   NSString *cacheDirectory = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0]; 
  
   18. 
   NSString *downloadPath = [cacheDirectory stringByAppendingPathComponent:@"xxx.zip"]; 
  
   19. 
   NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:downloadUrl]]; 
  
   20. 
   //檢查文件是否已經下載了一部分 
  
   21. 
   unsigned long long downloadedBytes = 0; 
  
   22. 
   if ([[NSFileManager defaultManager] fileExistsAtPath:downloadPath]) { 
  
   23. 
   //獲取已下載的文件長度 
  
   24. 
   downloadedBytes = [self fileSizeForPath:downloadPath]; 
  
   25. 
   if (downloadedBytes > 0) { 
  
   26. 
   NSMutableURLRequest *mutableURLRequest = [request mutableCopy]; 
  
   27. 
   NSString *requestRange = [NSString stringWithFormat:@"bytes=%llu-", downloadedBytes]; 
  
   28. 
   [mutableURLRequest setValue:requestRange forHTTPHeaderField:@"Range"]; 
  
   29. 
   request = mutableURLRequest; 
  
   30. 
   } 
  
   31. 
   } 
  
   32. 
   //不使用緩存，避免斷點續傳出現問題 
  
   33. 
   [[NSURLCache sharedURLCache] removeCachedResponseForRequest:request]; 
  
   34. 
   //下載請求 
  
   35. 
   AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request]; 
  
   36. 
   //下載路徑 
  
   37. 
   operation.outputStream = [NSOutputStream outputStreamToFileAtPath:downloadPath append:YES]; 
  
   38. 
   //下載進度回調 
  
   39. 
   [operation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead) { 
  
   40. 
   //下載進度 
  
   41. 
   float progress = ((float)totalBytesRead + downloadedBytes) / (totalBytesExpectedToRead + downloadedBytes); 
  
   42. 
   }]; 
  
   43. 
   //成功和失敗回調 
  
   44. 
   [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) { 
  
   45. 
     
   46. 
   } failure:^(AFHTTPRequestOperation *operation, NSError *error) { 
  
   47. 
     
   48. 
   }]; 
  
   49. 
   [operation start]; 
  
   50. 
   }

須要注意的是，此種寫法僅適用於下載zip包，由於下載其餘格式的文件有可能出現數據過多的狀況。當文件已經下載完成時，再次調用該函數，沒法判斷文件是否已經下載完整，因而會再次下載，此時服務器會報416錯，同時返回也會輸出到文件中，使得文件大小異常。可是zip格式不受影響。服務器

轉自：http://www.it165.net/pro/html/201403/10755.htmlapp