Take a look at Sencha Touch Profiles
If you are looking for a lovely explanation of how this could be implemented check => Loading different views for different profiles
Question
I am building a cross platform Application using Sencha Touch. The application is for both mobiles and tablets. The MainPage of the application contains a list and a form. Now I want that when the device is tablet, the list should appear in the left side of the device in 1/3rd of the screen width. and the form should appear in the remaining page. But when the device is mobile, entire screen should be filled with form only and I need to provide a button at the top of the page, clicking on which will open up the list. How should I proceed?
Solution
Take a look at Sencha Touch Profiles
If you are looking for a lovely explanation of how this could be implemented check => Loading different views for different profiles
OTHER TIPS
you can do this by checking the condition in initialize function on main page. And you can write your code by checking condition whether it is tablet or not.