iOS 应用开发中的断点续传实践总结详解手机开发

 // 1 指定下载文件地址 URLString  
 // 2 获取保存的文件路径 filePath  
 // 3 创建 NSURLRequest  
 NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:URLString]];  
 unsigned long long downloadedBytes = 0;  
 
 if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {  
 // 3.1 若之前下载过 , 则在 HTTP 请求头部加入 Range  
    // 获取已下载文件的 size  
    downloadedBytes = [self fileSizeForPath:filePath];  
 
    // 验证是否下载过文件 
    if (downloadedBytes > 0) {  
        // 若下载过 , 断点续传的时候修改 HTTP 头部部分的 Range  
        NSMutableURLRequest *mutableURLRequest = [request mutableCopy];  
        NSString *requestRange =  
        [NSString stringWithFormat:@"bytes=%llu-", downloadedBytes];  
        [mutableURLRequest setValue:requestRange forHTTPHeaderField:@"Range"];  
        request = mutableURLRequest;  
    }  
 }  
 
 // 4 创建 AFHTTPRequestOperation  
 AFHTTPRequestOperation *operation  
  = [[AFHTTPRequestOperation alloc] initWithRequest:request];  
 
 // 5 设置操作输出流 , 保存在第 2 步的文件中 
 operation.outputStream = [NSOutputStream  
 outputStreamToFileAtPath:filePath append:YES];  
 
 // 6 设置下载进度处理 block  
 [operation setDownloadProgressBlock:^(NSUInteger bytesRead,  
 long long totalBytesRead, long long totalBytesExpectedToRead) {  
 // bytesRead 当前读取的字节数 
 // totalBytesRead 读取的总字节数 , 包含断点续传之前的 
 // totalBytesExpectedToRead 文件总大小 
 }];  
 
 // 7 设置 success 和 failure 处理 block  
 [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation  
 *operation, id responseObject) {  
 
 } failure:^(AFHTTPRequestOperation *operation, NSError *error) {  
 
 }];  
 
 // 8 启动 operation  
 [operation start];

 // SWIFT  
 // 请求失败处理 
 func connection(connection: NSURLConnection,  
 didFailWithError error: NSError) {  
    self.failureHandler(error: error)  
 }  
 
 // 接收到服务器响应是调用 
 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  
 }  
 
 // 当服务器返回实体数据是调用 
 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)  
    }  
 }  
 
 // 下载完毕后调用 
 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  
 // 接收数据 
 func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask,  
 idReceiveData data: NSData) {  
    //. . .  
 }  
 // 接收服务器响应 
 func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask,  
 didReceiveResponse response: NSURLResponse, completionHandler:  
  (NSURLSessionResponseDisposition) -> Void) {  
    // . . .  
    completionHandler(.Allow)  
 }  
 
 // 请求完成 
 func URLSession(session: NSURLSession, task: NSURLSessionTask,  
  didCompleteWithError error: NSError?) {  
    if error == nil {  
        // . . .  
        self.successHandler(responseObject:self.fileName!)  
    } else {  
        self.failureHandler(error:error!)  
    }  
 }

 //SWIFT  
 
 //UI 触发 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)  
 }