如何使用 Java / Android 正确测量下载速度

How to correctly measure download speed with Java / Android

提问by Joffroi

I'm trying to perform an AsyncTask class in my Android application that analyzes the network connection speed in for downloading and uploading. I'm working on the download portion now, but I'm not getting results I expect. I'm testing on a Wifi network that gets 15Mbps down/up speeds consistently, however, the results I'm getting from my application are more around barely 1Mpbs. When I run the speed test apk on the device I'm testing on that gets around 3.5Mbps. The function works, just seems to be half the speed it should be. Should the following code produce accurate results?

我正在尝试在我的 Android 应用程序中执行一个 AsyncTask 类，该类分析下载和上传的网络连接速度。我现在正在处理下载部分，但没有得到预期的结果。我正在一个 Wifi 网络上进行测试，该网络的下降/上升速度始终如一，但是，我从我的应用程序中获得的结果几乎只有 1Mpbs。当我在我正在测试的设备上运行速度测试 apk 时，它的速度约为 3.5Mbps。该功能有效，但速度似乎只有其应有的一半。下面的代码应该产生准确的结果吗？

try {
           String DownloadUrl = "http://ipv4.download.thinkbroadband.com:8080/5MB.zip";
           String fileName = "testfile.bin";


           File dir = new File (context.getFilesDir() + "/temp/");
           if(dir.exists()==false) {
                dir.mkdirs();
           }

           URL url = new URL(DownloadUrl); //you can write here any link
           File file = new File(context.getFilesDir() + "/temp/" + fileName);


           long startTime = System.currentTimeMillis();
           Log.d("DownloadManager", "download begining: " + startTime);
           Log.d("DownloadManager", "download url:" + url);
           Log.d("DownloadManager", "downloaded file name:" + fileName);

           /* Open a connection to that URL. */
           URLConnection ucon = url.openConnection();

           //Define InputStreams to read from the URLConnection.
           InputStream is = ucon.getInputStream();
           BufferedInputStream bis = new BufferedInputStream(is);

           //Read bytes to the Buffer until there is nothing more to read(-1).  
           ByteArrayBuffer baf = new ByteArrayBuffer(1024);
           int current = 0;
           while ((current = bis.read()) != -1) {
              baf.append((byte) current);
           }
           long endTime = System.currentTimeMillis(); //maybe

           /* Convert the Bytes read to a String. */
           FileOutputStream fos = new FileOutputStream(file);
           fos.write(baf.toByteArray());
           fos.flush();
           fos.close();

          File done = new File(context.getFilesDir() + "/temp/" + fileName);
          Log.d("DownloadManager", "Location being searched: "+ context.getFilesDir() + "/temp/" + fileName);
          double size = done.length();
          if(done.exists()) {
              done.delete();
          }

          Log.d("DownloadManager", "download ended: " + ((endTime - startTime) / 1000) + " secs");
          double rate = (((size / 1024) / ((endTime - startTime) / 1000)) * 8);
          rate = Math.round( rate * 100.0 ) / 100.0;
          String ratevalue;
          if(rate > 1000)
             ratevalue = String.valueOf(rate / 1024).concat(" Mbps");
          else
             ratevalue = String.valueOf(rate).concat(" Kbps"); 
          Log.d("DownloadManager", "download speed: "+ratevalue);       
   } catch (IOException e) {
       Log.d("DownloadManager", "Error: " + e);
   }

Example output

示例输出

10-08 15:09:52.658: D/DownloadManager(13714): download ended: 70 secs
10-08 15:09:52.662: D/DownloadManager(13714): download speed: 585.14 Kbps

Thanks in advance for the help. If there is a better method, please let me know.

在此先感谢您的帮助。如果有更好的方法，请告诉我。

采纳答案by njzk2

Following on my comments, here is an example of how to read several bytes from the stream

根据我的评论，这是一个如何从流中读取几个字节的示例

//Define InputStreams to read from the URLConnection.
InputStream is = ucon.getInputStream();
BufferedInputStream bis = new BufferedInputStream(is);

//I usually use a ByteArrayOutputStream, as it is more common.
ByteArrayOutputStream baos = new ByteArrayOutputStream();
int red = 0;
// This size can be changed
byte[] buf = new byte[1024];
while ((red = bis.read(buf)) != -1) {
    baos.write(buf, 0, red);
}

What this does is it reads into a byte[] buffer, and return the amount of read bytes. This is in turn written to the OutputStream, specifying the amount of bytes to write.

它的作用是读入 byte[] 缓冲区，并返回读取的字节数。这依次写入 OutputStream，指定要写入的字节数。

ByteArrayOutputStreamalso have a toByteArraythat behaves similarly.

ByteArrayOutputStream也有一个toByteArray行为类似的。

Alternatively, you can also write directly to the file, if you consider that the write to file operation is significantly faster than the read function :

或者，您也可以直接写入文件，如果您认为写入文件操作明显快于读取功能：

// Simply start by defining the fileoutputstream
FileOutputStream fos = new FileOutputStream(file);
int red = 0;
// This size can be changed
byte[] buf = new byte[1024];
while ((red = bis.read(buf)) != -1) {
    // And directly write to it.
    fos.write(buf, 0, red);
}
long endTime = System.currentTimeMillis(); //maybe
// Flush after, as this may trigger a commit to disk.
fos.flush();
fos.close();

Moreover, if you really only care about the download speed, it is not mandatory to write to the file, or to anywhere, this would be sufficient :

此外，如果您真的只关心下载速度，则不需要写入文件或任何地方，这样就足够了：

long size = 0;
byte[] buf = new byte[1024];
while ((red = bis.read(buf)) != -1) {
    size += red;
}