title: Download and show the Thumbnail
body: <p>I try to download a picture from URL to SD card/Download.
  And I try to show its thumbnail in imageview.
  Now I had below code:</p>
  
  <pre><code>try {
  Download(URL);  //download picture to SD card/Download
  File myfile = new File(Environment.getExternalStorageDirectory() + "/Download/", filename);
  Drawable photo = null; 
  photo = Drawable.createFromPath(myfile.getPath());
  imageview.setBackgroundDrawable(photo);
  }
  </code></pre>
  
  <p>It show the original picture.
  But when the picture is large.
  The memory error occurs.
  So I want to show the smaller picture.
  How should I do to generate the thumbnail and show it?
  Or how to use the thumbnail generate by Android system?</p>