Android Basics

28 May 2020

Working through the Google codelabs tutorials, I am learning the basics about Android. It’s interesting to see how tightly coupled the app development process is with the underlying operating system, something that desktop development would never experience. I feel like I still don’t know enough about the strange syntaxes of Kotlin. Seems like a lot of method calls are used contextually, like cancelAll() just works because it’s inside a NotificationManager. This is surely easy to use, but it might be difficult to tell where the method definition comes from at a glance.

Intent

Intent is basically an entry point to your app, that captures the Application Context, and a specific Activity that this intent will launch. A PendingIntent will allow other applications or the OS to trigger your app, even if your app is not running. A Broadcast is a special Intent that mirror the pub-sub design pattern, and you can have BroadcastReceiver that process the incoming Intent.

Fragment

Fragment is basically a view, and the things that need to be started when running the view, such as creating a Notification Channel to send notifications, initialize a ViewModel to store UI data and such.

ViewModel

ViewModel serves to separate data from the UI. Since the UI might get redrawn because of screen-rotation, split-screen and such, we don’t want to lose the user entered data when that happens. ViewModel helps store that data.

Strings

No strings that show up in the UI should be in the code. The standard android pattern stores all the strings in a separate file, and retrieve them in code by applicationContext.getString(R.string.something). This allows easy translation and changes to wording, since they are all centralized.