title: getFragmentManager() cannot resolved on Custom Dialog
body: <p>I have a custom DialogBox,</p>
  
  <pre><code>public class DialogBoxLogInPop extends DialogBox implements View.OnClickListener {
  //...some code...
  }
  </code></pre>
  
  <p>On the main activity there is a button, OnClicked on that button a Sign In Dialog Box will pop out. and when the condition is reach, it will prompt the user to a certain fragment.</p>
  
  <pre><code>if (username.trim().length() &gt; 0 &amp;&amp; password.trim().length() &gt; 0) {
          if (tTable_Contacts.checkifexist(username, password)) {
  
              FragmentManager fragmentManager = getFragmentManager();
              fragmentManager.beginTransaction()
                      .replace(R.id.content, mFragment_member).addToBackStack(null).commit();
  
              dismiss();
  
          } else {
              ETLoginDialogEmail.setError("Username is not valid.");
              ETLoginDialogPassword.setError("Password is not valid.");
  
          }
      } 
  </code></pre>
  
  <p>My problem is that, the function getFragmentManager() is cannot be resolved.
  Can anyone help me how to fix this problem?</p>
  
  <p>Thank you in advance.</p>