title: updating too much notifications cause lag, how to improve it?
body: <p>I am downloading multiple files in parallel (more than <strong>10</strong>) using Async task (The code is in a different .java file than the Main.java).<br>
  I spawn many Async task and each task will call onProgress about every 2 seconds<br>
  in the Async task onProgress method, it will update a text and progress bar in the notification bar </p>
  
  <pre><code>Main.notification.contentView.setProgressBar(R.id.status_progress, 100, percentCompleted, false); // percentCompleted is calculated
  Main.notification.contentView.setTextViewText(R.id.status_text, title);
  Main.nm.notify(value, Main.notification);
  </code></pre>
  
  <p>Note that I declare and initialize the "notification" and "nm" in Main.java as public static. (so I can easily call them in my async task which is in another .java file)</p>
  
  <pre><code>public static Notification notification;
  public static NotificationManager nm;
  </code></pre>
  
  <p>When I am downloading about <strong>5</strong> files in parallel, it is still working fine (no obvious lag).<br>
  But when I am downloading more than <strong>10</strong> files in parallel, the notification bar become very lag.<br>
  It even crashed when when I am downloading <strong>20</strong> files in parallel with error "unfortunately system ui has stopped", and my notification bar disappear totally (must reboot phone).</p>
  
  <p>What is the better way of updating multiple notification like this, but with no lag?   </p>
  
  <p>Please note that the lag is not caused by the download in the Async task. I have tried the download without showing notification in notification bar, and it has no lag at all. (Galaxy S3 Quad Cores Exynos)</p>
  
  <p><img src="https://i.stack.imgur.com/EX3dQ.png" alt="enter image description here"></p>