Question

我正在尝试在我的Android应用程序中执行AsyncTask类，该类分析下载和上载的网络连接速度。我现在正在处理下载部分，但我没有得到我期望的结果。我正在Wifi网络上进行测试，该网络可以始终如一地获得15Mbps的下行/上行速度，但是，我从应用程序中获得的结果大约只有1Mpbs。当我在设备上运行速度测试apk时，我正在测试它大约3.5Mbps。该功能起作用，似乎只是它应该的速度的一半。以下代码是否应该产生准确的结果？

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);
   }

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

提前感谢您的帮助。如果有更好的方法，请告诉我。

Answer 1

在我的评论之后，这是一个如何从流中读取几个字节的例子

//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);
}

这样做是读入byte []缓冲区，并返回读取字节数。然后将其写入OutputStream，指定要写入的字节数。

ByteArrayOutputStream也有toByteArray行为相似。

或者，如果您认为写入文件操作比读取函数快得多，您也可以直接写入文件：

// 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();

此外，如果您真的只关心下载速度，则不必写入文件或任何地方，这就足够了：

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

如何使用Java / Android正确测量下载速度

1 个答案: