title: Activity doesn't start after it started once
body: <p>My project starts an activity (say A) from <code>Application</code> class, some option in the activity A needs to launch another activity (say B), now depends on some network conditions, <code>application</code> class may need to start activity A (currently activity B is shown). but this time (this is the second time that activity B is going to start) activity B is not shown. I use the following code to start activity:
  <br /><br /></p>
  
  <pre><code>Intent main_act= new Intent(app.this,main_activity.class);
  startActivity(main_act);
  </code></pre>