title: Saving transaction like header and detail using volley
body: <p>I am new for using <code>Volley</code> in <code>Android</code>. Now I want to save my transaction with these steps:  </p>
  
  <ol>
  <li><p><code>Android</code> will call the service to get <code>RequestID</code> ( auto generated id from system ), then</p></li>
  <li><p><code>RequestID</code> will be used as one of parameter for any execution of detail transaction, then</p></li>
  <li><p>If all detail transaction is successfully executed, go to another activity.</p></li>
  </ol>
  
  <p>FYI : I use <code>ProgressDialog</code> for updating any progress for steps above.</p>
  
  <p>My theory is like this:</p>
  
  <ol>
  <li><p>I set message of Progress Dialog like "Sending your request to server", then</p></li>
  <li><p>I use String Request to executed the header request, then</p></li>
  <li><p><code>onResponse</code> function of header execution, I get the Response ID from returned JSON, then</p></li>
  <li><p>try to add to <code>RequestQueue</code> again of any detail transaction with specified param ( like <code>RequestID</code>, etc ) and</p></li>
  <li><p>I also check if <code>onResponse</code> of any executed detail transaction if it is last detail transaction or not,</p></li>
  <li><p>If it is last detail transaction, I try to dismiss Progress Dialog.</p></li>
  </ol>
  
  <p>When I run the application, it stuck at second detail transaction ( I have 3 detail transaction ).</p>
  
  <p>How can I set the sequence of <code>volley</code> request since I know that <code>volley</code> is asynchronous task, that can't predict the sequence of execution?</p>
  
  <p>If you need the code, please let me know.</p>
  
  <p>Thanks.</p>