Writing our first Kotlin code

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

Tip

We know that to execute the code in a function, we need to call it. We have wired our buttons up to call a couple of functions, such as topClick and bottomClick. Soon, we will write these functions. But who or what is calling onCreate? The answer to this mystery is that Android itself calls onCreate in response to the user clicking on the app icon to run the app. In Chapter 6, The Android Lifecycle, we will look deeper, and it will be clear what exactly the 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...