如何使用Java/Android正確測量下載速度

Question

我正在嘗試在我的Android應用程序中執行一個AsyncTask類，以分析下載和上傳的網絡連接速度。我現在正在下載部分，但我沒有得到我期望的結果。我正在一個Wifi網絡上進行測試，這個網絡的速度一直保持在15Mbps以下，但是從我的應用程序中得到的結果更差不多在1pbs左右。當我在設備上運行速度測試apk時，我測試的速度大約爲3.5Mbps。該功能起作用，似乎只有它的一半速度。下面的代碼應該產生準確的結果嗎？

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); 
    } 

實施例輸出

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 

預先感謝您的幫助。如果有更好的方法，請告訴我。

Answer 1

繼我的意見，在這裏是如何從流

//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); 
} 

這樣做是它讀成一個byte []緩衝區中讀取幾個字節，並返回讀取的字節量的例子。這又被寫入到OutputStream中，指定要寫入的字節數量。

ByteArrayOutputStream也有一個toByteArray行爲相似。

另外，您也可以直接寫入文件，如果你考慮到文件操作寫比讀功能顯著快：

// 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，如果你真的只關心下載速度，它不是強制性的寫入文件或任何地方，這將是足夠的：

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