In the first five chapters, we got quite proficient with a whole array of widgets and other UI elements. We also built a broad selection of UI layouts. In this chapter and the previous three, we have explored Java and the Android Activity life cycle in quite significant depth, especially considering how quickly we have done it.

We have, to a small extent, interacted between our Java code and our UI. We have called our methods by setting the onClick attribute and we have loaded our UI layouts using the setContentView method. We haven't, however, really made a proper connection between our UI and our Java code.

What we really need to do now is bring these things together so that we can begin to display and manipulate our data using the Android UI. To achieve this, we need to understand a bit more about classes.

Classes have been lurking in our code since Chapter 1, Beginning Android and Java, and we have even used them a bit. Hitherto, however, we haven't tackled them properly other than constantly referring to Chapter 10, Object-Oriented Programming. In the next chapter (number 10), we will quickly get to grips with classes and then we can finally start to build apps where the UI designs and our Java code work in perfect harmony.