Note that we create an instance of our KeypadAdapter on Line 25 and set this instance as the adapter of our GridView on Line 28. Another thing I want you to notice in the code above is the findViewById call on Line 21. As I noted in previous section, we use the value of the id attribute we have assigned to our GridView in our layout XML (main.xml).
When you run the TouchCalculator at this point, you will see the following UI which is almost the same as our mock up.