Writing our first Java code

So, we now know the code that will output to logcat or the user's screen. But where do we put the code? To answer this question, we need to understand that the onCreate method in HelloWorldActivity.java executes as the app is preparing to be shown to the user. So, if we put our code at the end of this method, it will run just as the user sees it. Sounds good.

Tip

We know that to execute the code in a method, we need to call it. We have wired our buttons up to call a couple of methods, topClick and bottomClick. Soon, we will write these methods. But who or what is calling onCreate? The answer to this mystery is that Android itself calls onCreate in response to the user clicking the app icon to run the app. In Chapter 6, The Android Lifecycle, we will look deeper, and it will be clear exactly what code executes and when. You don't need to completely comprehend this now. I just wanted to give you an overview of what was going on.

Let's quickly try this...