iOS 應用開發中的斷點續傳實踐總結

 // 1 指定下載檔案地址 URLString 
 // 2 獲取儲存的檔案路徑 filePath 
 // 3 建立 NSURLRequest 
 NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:URLString]]; 
 unsigned long long downloadedBytes = 0; 

 if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) { 
 // 3.1 若之前下載過 , 則在 HTTP 請求頭部加入 Range 
    // 獲取已下載檔案的 size 
    downloadedBytes = [self fileSizeForPath:filePath]; 

    // 驗證是否下載過檔案
    if (downloadedBytes > 0) { 
        // 若下載過 , 斷點續傳的時候修改 HTTP 頭部部分的 Range 
        NSMutableURLRequest *mutableURLRequest = [request mutableCopy]; 
        NSString *requestRange = 
        [NSString stringWithFormat:@"bytes=%llu-", downloadedBytes]; 
        [mutableURLRequest setValue:requestRange forHTTPHeaderField:@"Range"]; 
        request = mutableURLRequest; 
    } 
 } 

 // 4 建立 AFHTTPRequestOperation 
 AFHTTPRequestOperation *operation 
  = [[AFHTTPRequestOperation alloc] initWithRequest:request]; 

 // 5 設定操作輸出流 , 儲存在第 2 步的檔案中
 operation.outputStream = [NSOutputStream 
 outputStreamToFileAtPath:filePath append:YES]; 

 // 6 設定下載進度處理 block 
 [operation setDownloadProgressBlock:^(NSUInteger bytesRead, 
 long long totalBytesRead, long long totalBytesExpectedToRead) { 
 // bytesRead 當前讀取的位元組數
 // totalBytesRead 讀取的總位元組數 , 包含斷點續傳之前的
 // totalBytesExpectedToRead 檔案總大小
 }]; 

 // 7 設定 success 和 failure 處理 block 
 [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation 
 *operation, id responseObject) { 

 } failure:^(AFHTTPRequestOperation *operation, NSError *error) { 

 }]; 

 // 8 啟動 operation 
 [operation start];

 // SWIFT 
 // 請求失敗處理
 func connection(connection: NSURLConnection, 
 didFailWithError error: NSError) { 
    self.failureHandler(error: error) 
 } 

 // 接收到伺服器響應是呼叫
 func connection(connection: NSURLConnection, 
  didReceiveResponse response: NSURLResponse) { 
    if self.totalLength != 0 { 
        return 
    } 

    self.writeHandle = NSFileHandle(forWritingAtPath: 
    FileManager.instance.cacheFilePath(self.fileName!)) 

    self.totalLength = response.expectedContentLength + self.currentLength 
 } 

 // 當伺服器返回實體資料是呼叫
 func connection(connection: NSURLConnection, didReceiveData data: NSData) { 
    let length = data.length 

    // move to the end of file 
    self.writeHandle.seekToEndOfFile() 

    // write data to sanbox 
    self.writeHandle.writeData(data) 

    // calculate data length 
    self.currentLength = self.currentLength + length 

    print("currentLength\(self.currentLength)-totalLength\(self.totalLength)") 

    if (self.downloadProgressHandler != nil) { 
        self.downloadProgressHandler(bytes: length, totalBytes: 
        self.currentLength, totalBytesExpected: self.totalLength) 
    } 
 } 

 // 下載完畢後呼叫
 func connectionDidFinishLoading(connection: NSURLConnection) { 
    self.currentLength = 0 
    self.totalLength = 0 

    //close write handle 
    self.writeHandle.closeFile() 
    self.writeHandle = nil 

    let cacheFilePath = FileManager.instance.cacheFilePath(self.fileName!) 
    let documenFilePath = FileManager.instance.documentFilePath(self.fileName!) 

    do { 
        try FileManager.instance.moveItemAtPath(cacheFilePath, toPath: documenFilePath) 
    } catch let e as NSError { 
        print("Error occurred when to move file: \(e)") 
    } 

    self.successHandler(responseObject:fileName!) 
 }

 // SWIFT 
 // 接收資料
 func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, 
 idReceiveData data: NSData) { 
    //. . . 
 } 
 // 接收伺服器響應
 func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, 
 didReceiveResponse response: NSURLResponse, completionHandler: 
  (NSURLSessionResponseDisposition) -> Void) { 
    // . . . 
    completionHandler(.Allow) 
 } 

 // 請求完成
 func URLSession(session: NSURLSession, task: NSURLSessionTask, 
  didCompleteWithError error: NSError?) { 
    if error == nil { 
        // . . . 
        self.successHandler(responseObject:self.fileName!) 
    } else { 
        self.failureHandler(error:error!) 
    } 
 }

 //SWIFT 

 //UI 觸發 pause 
 func pause(){ 
    self.downloadTask?.cancelByProducingResumeData({data -> Void in 
        if data != nil { 
 data!.writeToFile(FileManager.instance.cacheFilePath(self.fileName!), 
 atomically: false) 
 } 
        }) 
    self.downloadTask = nil 
 } 

 // MARK: - NSURLSessionDownloadDelegate 
 func URLSession(session: NSURLSession, downloadTask: 
 NSURLSessionDownloadTask, didWriteData bytesWritten: Int64, 
 totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) { 
    if (self.downloadProgressHandler != nil) { 
        self.downloadProgressHandler(bytes: Int(bytesWritten), 
         totalBytes: totalBytesWritten, totalBytesExpected: totalBytesExpectedToWrite) 
    } 
 } 

 func URLSession(session: NSURLSession, task: NSURLSessionTask, 
 didCompleteWithError error: NSError?) { 
    if error != nil {//real error 
        self.failureHandler(error:error!) 
    } 
 } 

 func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, 
  didFinishDownloadingToURL location: NSURL) { 
    let cacheFilePath = FileManager.instance.cacheFilePath(self.fileName!) 
    let documenFilePath = FileManager.instance.documentFilePath(self.fileName!) 
    do { 
        if FileManager.instance.fileExistsAtPath(cacheFilePath){ 
            try FileManager.instance.removeItemAtPath(cacheFilePath) 
        } 
        try FileManager.instance.moveItemAtPath(location.path!, toPath: documenFilePath) 
    } catch let e as NSError { 
        print("Error occurred when to move file: \(e)") 
    } 
    self.successHandler(responseObject:documenFilePath) 
 }