About a week ago, someone on /r/androiddev asked the question “What are the things that every Junior Android Developer should know?”. Being the kind of guy that I am, I was browsing the subreddit at work (whilst compiling, obviously) and got an answer in early which people seemed to like a lot. So this is mostly just me expanding on my points.

Skillset

If you’re looking to come onboard as a Junior, there’s a few things that I’d expect you to know. None of them particularly in-depth, of course (not in a patronising way), but for me to see that you’re interested in the field and learning as much as you can, I’d want to see at least some low-level knowledge in the following areas:

The Activity Lifecycle

It’s Android. There’s no getting away from it. These events are absolutely crucial to developing an app that doesn’t crash when you accidentally rotate the screen because you’re browsing in bed.

On first glance this diagram doesn’t look all that friendly:

But in reality, I don’t expect a Junior to know the whole thing off by heart. As long as you’re aware of onCreate, onPause, onResume and onDestroy, what causes them and their implications, then you’re off to a good start. If you’re a bit unsure, check out the official docs. If you give an example as to how the lifecycle could cause a memory leak, I’d be mightily impressed.

Android Components

The building blocks of any app. There’s only 4 major components: Activities, Services, Content Providers and Broadcast Receivers, and each has an important part to play in creating an Android app. You won’t necessary need all of them in a single app (for instance, in my professional career I’ve never needed to write a Content Provider), but I’d still 100% like to see that a candidate can explain roughly what each one does and what they might use one for.

Persistence Options

There’s a handful of options for persisting data on Android, and each has their own pros, cons and use-cases. There’s a helpful guide on the Android Developer website which explains how to use each type, and again I’d want to see if you can recall them and in broad strokes what you might use each type for.

Networking

This is a biggie and there’s an awful lot to know, but for someone wanting to go for a Junior position there’s only a couple of things that I’d deem essential.
Basic REST knowledge is a must, and if you can’t make a simple GET or POST request from an Android app then you’ll want to get back to hacking together some basic apps. Pretty much every app I can think of makes REST requests, and this knowledge is fundamental. Android’s Volley class is a good place to start if you want to learn the absolute basics, but in an ideal world you’ll know that it’s a pretty outdated way of doing things.

As such, if you’ve used an alternative such as Retrofit then you’ll be in a good place. There are a handful of other possible ways to do networking on Android but almost all of them are pretty niche now – Retrofit is super simple, pairs nicely with the power and flexibility of OkHttp and is regularly updated with great features by the extraordinary team at Square.

Alongside that, some knowledge of serialisation would be great. Experience of Gson, Jackson, Moshi or similar is a great sign, as nobody in 2017 should be plucking values manually out of JSON.

Android Studio Skills

Android Studio has come an awfully long way since the first alpha rolled out several years ago now, back in the dark days when everyone used Eclipse. Even as a Junior, I’d want to see some indication that you know the program pretty well – navigating everywhere by hand is a bad sign and horribly unproductive, so I like to see people using shortcuts a lot. In fact one of my favourite interview questions is to ask a candidate's favourite shortcut, as there are so many that I regularly learn something new.

To be clear, I’m not expecting you to be a ninja by any stretch. But knowing your tools to a reasonable level shows interest in the craft. Knowing a few of these will make you dramatically more productive and make pair programming much less painful.
If you’re still using IntelliJ that’s fine too, and if you’re using Eclipse… well, I think I’d be more curious as to why than anything else.

Git

Another important one. Amazingly there are people these days who work without using a VCS system, and that’s a really big red flag for me. If you’re not using git right now you should be, and whilst the learning curve is a little steep the payoff is huge. Admittedly it can be difficult to see the benefit if you’ve solely worked by yourself up to this point – until you’ve realised that you’ve made a horrible error 6 hours into refactoring and want to revert to how the app was when it worked. This guide is no-nonsense and will get you started, and to be honest you don’t need any more than that.

Even if you just use git from a GUI like the excellent SourceTree, that’s fine with me.

Of course there are a handful of other VCS systems out there and knowing any of them is great – but git is the most widely used by far.

Design Patterns

This one is perhaps less essential, and I’m sure many use some of the more common patterns without realising that they’re classified as ‘design patterns’. But if you know the basics such as Builders, Singletons and Factory Methods and where you might use them (or even where you can find an example in the Android SDK), then that’s great.

If you happen to own or even just know about The Gang of Four or Effective Java, bonus points for you. Talking of which:

Bonus Points

• You’ve ever written a Unit test, or understand why writing them on Android can be so amazingly difficult
• You own at least one of the all-time classic development books
• You’ve dabbled with other languages, Kotlin in particular
• You’ve published something to the Play Store

Other Stuff

Of course there are other attributes that I really like to see in someone applying for a Junior Developer role, which can mostly be filed under ‘soft skills’.
In my opinion, the role of a Junior is mostly to learn as much as they can as quickly as possible so that they can contribute meaningfully to the product. By and large, Juniors are assigned initially simple work by a Senior that will gradually take them deeper and deeper into the stack, building the developers confidence and skills along the way.

As such, to be a good Junior I think it’s critical to have good autodidact skills, and to an extent you can prove that with what I would call peripheral knowledge. You might not know how to use it, but you know that RxJava is so hot right now and it’s been on your TODO list for some other time. A lot of blogs talk about Kotlin, so that’s on there too. You’ve heard about the awful world where we had to maintain compatibility with Gingerbread. You have some idea of what the next version of Android is bringing to the table. That sort of thing.

Anything that shows that you’ve read around a bit is a really great sign, even if you’re only aware of some libraries/techniques/common issues/features.
To that end, I’d hope that you’re signed up to the excellent Android Weekly, browse /r/androiddev, and can maybe name a couple of the most influential people in the industry and follow their blogs, Mediums, Twitter accounts etc. Maybe you listen to Fragmented too.

Ultimately what I want to see more than almost anything else is some passion for the platform. I’ve been tinkering with Android for 6 years now and developing for 4, and I still get excited when I see an update from the Android team. I wasn’t expecting the Android O preview until months after it was actually announced, and I immediately flashed the (rather unstable) alpha to my device because I just had to have a play and find out what was new.

I love checking out new devices when they get announced, I race to get the latest updates from APKMirror, I’ve flashed countless custom ROMs and bricked a few devices over the years. I always watch I/O when it’s on, and one day I’ll finally make the pilgrimage to Mountain View. I own several Android t-shirts, which for an adult male is ridiculous. If you can relate to any of that; you’re my kind of developer.

Android is the most rapidly adopted technology in history, and I’m excited to be involved in it. If that excites you and you can tick off the majority of the boxes I’ve listed here then I’d like to work with you, and I look forward to teaching you as much as I can about the platform that I love.