   <div>
  Added in <a href="../../../../guide/topics/manifest/uses-sdk-element.html#ApiLevels">API level 1</a></div>
        
  

      </div>
    <div class="jd-details-descr">
      
  <div class="jd-tagdata jd-tagdescr"><p>Attempts to cancel execution of this task.  This attempt will
 fail if the task has already completed, has already been cancelled,
 or could not be cancelled for some other reason. If successful,
 and this task has not started when <code>cancel</code> is called,
 this task should neve