如何获取GTMSessionFetcher下载进度

Question

为了下载一个文件，我喜欢这样：

 GTMSessionFetcher *fetcher = [self.service.fetcherService fetcherWithURLString:url];
    [fetcher beginFetchWithCompletionHandler:^(NSData *data, NSError *error)
        {
    [data writeToFile:localFilePath atomically:YES];
    }];

文件已成功下载，但如果您这样做，我无法获得下载进度。

fetcher.downloadProgressBlock  = ^(int64_t bytesWritten, int64_t totalBytesWritten, int64_t totalBytesExpectedToWrite)
    {
        NSLog(@"bytesWritten = %lld",bytesWritten);
        NSLog(@"totalBytesWritten = %lld",totalBytesWritten);
        NSLog(@"totalBytesExpectedToWrite = %lld",totalBytesExpectedToWrite);
    };

我做错了什么？

我找到了工作解决方案.

float totalBytesExpectedToWrite = [file.size floatValue]; //file - it's GTLDriveFile to download 
[fetcher setReceivedProgressBlock:^(int64_t bytesWritten, int64_t totalBytesWritten)
{
    NSLog(@"Download progress - %.0f",(totalBytesWritten * 100)/totalBytesExpectedToWrite);
}];

Answer 1

根据这个文档，可选的接收到的数据选择器可以用setReceivedDataSelector设置，并且应该具有签名：

- (void)myFetcher:(GTMSessionFetcher *)fetcher receivedData:(NSData *)dataReceivedSoFar;

下面是示例代码：

self.fetcher = [GTMHTTPFetcher fetcherWithRequest:request];
[self.fetcher setReceivedDataBlock:^(NSData *data) {
    float percentTransfered = self.fetcher.downloadedLength * 100.0f / self.fetcher.response.expectedContentLength;
    // Do something with progress
}

如果下载的文件大小未知，expectedContentLength将返回-1。

还找到了这个线程，它提供了用于回调进度的代码：

GTMHTTPFetcher *fetcher =
    [self.driveService.fetcherService fetcherWithURLString:downloadURL];
GTLDriveFile *file = [driveFiles objectAtIndex:indexPath.row];

[fetcher setReceivedDataBlock:^(NSData *data) {
    NSLog(@"%f%% Downloaded", (100.0 / [file.fileSize longLongValue] * [data length]));
}];