如何在下载文件时为NSURLConnection创建进度条？ [英] How to make an progress bar for an NSURLConnection when downloading a file?

问题描述

我想在使用NSURLConnection进行下载时显示进度条。当我从服务器获取数据时，我可以更新每个收到的包的UI。但问题是：我如何计算出已经有多少数据，以及需要下载多少数据？可能以字节为单位......然后我必须做一些数学计算以获得百分比？

I want to show up an progress bar while a download with NSURLConnection is happening. As I am getting data from the server, I could update the UI for every received package. But the problem is: How do I figure out how much data I have already, and how much data has to be downloaded? Probably in bytes... And then I have to do some math to get the percentage?

推荐答案

在你的<$ c $中c> NSURLConnection 委托，实现类似的内容以查找总内容长度。服务器必须支持这一点，但它很可能与静态内容一起使用：

In your NSURLConnection delegate, implement something like this to find out the total content length. The server has to support this, but it will most likely work fine with static content:

- (void)connection: (NSURLConnection*) connection didReceiveResponse: (NSHTTPURLResponse*) response
{
    statusCode_ = [response statusCode];
    if (statusCode_ == 200) {
        download_.size = [response expectedContentLength];
    }
}

然后像这样更新进度：

- (void) connection: (NSURLConnection*) connection didReceiveData: (NSData*) data
{
    [data_ appendData: data];
    download_.progress = ((float) [data_ length] / (float) download_.size);
    // Broadcast a notification with the progress change, or call a delegate
}

在我的情况下，我有一个下载实例，其中包含 size 和 progress 属性。它们由全局 DownloadManager 对象拥有，该对象将负责通知感兴趣的各方下载进度或状态更改。

In my case I have a download instance that has size and progress properties. They are owned by a global DownloadManager object that will take care of notifying interested parties of the download progress or state changes.

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