title: next and previous buttons in walkthrough
body: <p>Am trying to build an app intro walkthrough using the flutter package:   <code>transformer_page_view</code> like this:</p>
  
  <pre><code>return new Scaffold(
      backgroundColor: Color(0xFF202020),
      body: new TransformerPageView(
          loop: true,
          transformer: new ThreeDTransformer(),
          itemBuilder: (BuildContext context, int index) {
            return Container(
              height: MediaQuery.of(context).size.height,
              width: MediaQuery.of(context).size.width,
              color: Colors.white,
              child: Stack(
                children: &lt;Widget&gt;[
                  .....
                        ],
                      ),
                    ),
                    alignment: Alignment.bottomCenter,
                  )
                ],
              ),
            );
          },
          itemCount: 2));
  </code></pre>
  
  <p>everything is working fine as i wanted.. but i have a next and previous buttons... i want when click on next it goes to index = 1 and when click on previous it goes to index = 0 ...</p>
  
  <p>i tried something like this:</p>
  
  <pre><code>onPressed: () {
     if (index == 0 ){
        loginPage();
     }else{
        setState(() {
          index = 0;
        });
     }
   },
  </code></pre>
  
  <p>but this is didn't work ... any ideas how to achieve this?</p>