title: Action bar supplied by the window decor issue
body: <p>I am getting following error </p>
  
  <p>Caused by: java.lang.<strong>IllegalStateException</strong>: This Activity already has an action bar supplied by the window decor. Do not request Window.<strong>FEATURE_ACTION_BAR</strong> and set windowActionBar to false in your theme to use a Toolbar instead. </p>
  
  <p>I have tried answers like this</p>
  
  <p><strong>getSupportActionBar().hide();
  before setContentView(R.layout.activity_main);</strong> </p>
  
  <p>but not sloved.how to solve?</p>