title: how to add back button in navigation bar in sencha touch?
body: <p>In <code>Innerdata.js</code>, i have a <code>a</code> tag and on tap event i navigate it to the <code>Group.js</code>. </p>
  
  <p><code>Gruop.js</code> contain some html.I try to add here navigation bar with back button. Here the only Navigation bar is display no back button. Now this is where I fall down, I can't figure out why the Back button is not display.</p>
  
  <p>I am trying to add Back button in navigation bar in <code>Group.js</code> page so when i click this button i navigate to the <code>Inner.js</code> page.so what is the problem  here?</p>
  
  <p><code>Inner.js:</code></p>
  
  <pre><code>Ext.define('chat.view.Inner', {
      extend: 'Ext.Panel',
      xtype:'Inner',
      config: {
          items: [
              {xtype:'Innerdata'}
          ]
      }
  });
  </code></pre>
  
  <p><code>Innerdata.js:</code></p>
  
  <pre><code>Ext.define('chat.view.Innerdata',{
      extend:'Ext.Panel',
      xtype:'Innerdata',
      config: {
          items: [
              {
                  html:'&lt;a class="groupimg"&gt;&lt;img src="stylesheets/images/groupchat.png"/&gt;&lt;/a&gt;',
                  listeners: [
                  {
                      element: 'element',
                      delegate: 'a.groupimg',
                      event: 'tap',
                      fn: function() {
                          console.log('One!');
                          Ext.Viewport.setActiveItem(Ext.create('chat.view.Group'));
                      }
                  }
                  ]
              },
          ]
      }
  });
  </code></pre>
  
  <p><code>Group.js:</code></p>
  
  <pre><code>Ext.define('chat.view.Group', {
      extend: 'Ext.navigation.View',
      //extend: 'Ext.Panel',
      xtype:'Group',
  
      config:{
          items: [
                  {html:'&lt;div&gt;Hello Hello Hello Hello&lt;/div&gt;'}
                      ]
      },
      onBackButtonTap:function(){
          this.callParent(arguments); 
      }
  
  });    
  </code></pre>
  
  <p>here is the screen shot of <code>Group.js</code> page, i am trying to add Back button in Blue bar.
  <img src="https://i.stack.imgur.com/HSJMt.png" alt="enter image description here"></p>