title: Reorder existing activity to the top when start it from other applications
body: <p>I have application A, and application B.</p>
  
  <p>In A, it has a, b, c activities.</p>
  
  <p>In B, it has x activity and there is a button to launch b activity in A.</p>
  
  <p>Assume in back stack there are already activities a, b, c (c at the top) in task 1.</p>
  
  <p>Now get c to start an activity x, result in x is created in task2. (Based on what I read from <a href="https://inthecheesefactory.com/blog/understand-android-activity-launchmode/en" rel="nofollow">the introduction</a> on lollipop).</p>
  
  <p>Then click the button in x, it will start b activity. b is then created in a separate task. I consider it normal because the launch mode is standard. If I launch b with <code>Intent.FLAG_ACTIVITY_BROUGHT_TO_FRONT</code> flag (For some reasons, I cannot give b <code>singleTask</code> launch mode, so use the flag instead). b is brought to front, however, c is killed (Based on what I read, this is expected behavior). </p>
  
  <p>Now I want to know how can I just reorder b to the top without destroying c? which will make the back stack become a, c, b.</p>
  
  <p>I have tried <code>FLAG_ACTIVITY_REORDER_TO_FRONT</code> but does not work. </p>