Android crash course

https://tech.showmax.com
@ShowmaxDevs
Android crash course
From zero to hero
michal.ursiny@showmax.com
Sample project:
https://github.com/Showmax/GithubUsersSearch

@ShowmaxDevs
Why develop for Android
● Because android rules! At least for Showmax users #1
platform
● Development easily available on any platform, be it
Windows, Linux, MacOS, ChromeOS
● Vast target audience with variety of devices and form
factors, phones, tablets, wear os (watches), android TVs,
android auto, IOT

@ShowmaxDevs
How to start - Android Studio
● Just download Android Studio - official IDE based on IntelliJ
IDEA
● Configure your emulator or enable developer mode on your
device
● Get acquainted with Android Studio

@ShowmaxDevs
Kotlin vs Java
● Code compiled to JAVA bytecode whatever you write your
app with
● Kotlin resolves nullability issue - forces you to avoid dreaded
NullPointerException in compile time and has number of
features that helps you write more concise code (data classes)
● However, Java is still fully supported and some newer Java
APIs are available

@ShowmaxDevs
You know why and how
Let’s look deeper into features and specifics of Android
development

@ShowmaxDevs
Start new project from template
Good as a starting point
Definitely not a complete solution,
often a bit outdated.

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Task #1
● Create a new project from template
● Run on emulator / device
● Try to modify some title/string

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What version ?
● Basically you don’t want to support
anything older than 5.0 from technical
point of view, business-wise at Showmax
we do support from 4.4 and it’s pain
● Starting 5.0 Android has new runtime
called ART with much better memory
handling / garbage collection + a lot of
improvements in UI, support for
VectorDrawables

@ShowmaxDevs
New APIs - not available on older versions ?
● Often you will notice that used classes are not from platform
API, but rather from compatibility libraries (AppCompat,
AndroidX), which provides compatible back-ported
versions/layers, which enables you to write code knowing it
will run on older versions as well, maybe sometimes with
some degradation; some components exists only in these
libraries and aren’t actually part of platform (eg.:
ConstraintLayout), but de-facto considered as such)

@ShowmaxDevs
Project structure overview
● Different views on project - android view vs. project view
● app module
● src - your kotlin/java source code
● res - your resources, images, strings, values
● AndroidManifest.xml - defines entry point to your app
● build.gradle under your app module - build & dependencies
configurations

@ShowmaxDevs
Basic building blocks of Android app
Application
Activity
Fragment
View
View
Activity
Fragment
Fragment
View
View
Others: Services, Broadcast receivers, Content Providers,... we ignore here
You may think of Activity
like screen; Activity can
contain one or multiple
Fragments for better re-
usability
View is like Button,
TextView, etc.

@ShowmaxDevs
Fragments reusability

@ShowmaxDevs
Build UI
● Layouts are written in XML using build in Android Studio
Editor
● Nowadays your root element is often ConstraintLayout and all
its children are laid out by setting up constraints
● ViewGroup(s): ConstraintLayout, LinearLayout,
FrameLayout,... - may contain multiple other View(s)

@ShowmaxDevs
Task #2 - build simple UI
1. Edit layout file from newly created project, make sure your
root element is ConstraintLayout
2. Add EditText and Button constrained horizontally and
vertically
3. Attach OnClickListener to Button and display Toast

@ShowmaxDevs
Binding views
● Every view has to have an id to be viewable
● Oldschool findViewById - always an option
● ViewBinding - sweet spot
● DataBinding
● 3rd party tools like Butterknife
● Jetpack Compose

@ShowmaxDevs
Themes & Styles
Application has a root theme, which defines basic look & feel
Material Components library recommended, provides latest
updated components
https://github.com/material-components/material-components-
android/blob/master/docs/getting-started.md

@ShowmaxDevs
Task #3: change to Material theme
1. Add material components library
2. Change application theme
3. Update layout to use TextInputLayout / TextInputEditText
instead of plain EditText

@ShowmaxDevs
Take advantage of Resource system
● drawables - your images/vector drawables
● layouts
● values - strings, dimens, integers, bools
Use qualifiers to your advantage:
● Locales - values-cs-rCZ
● Orientation - layout-land / layout-port
● Display size - layout-sw600 (smallest-width)

@ShowmaxDevs
Device independent pixels
As different devices have different screen sizes and density of
pixels, we are avoiding pixels, but rather using dp - device
independent pixels, so that the sizes are relatively same on
different devices.
For fonts there are sp - which are scaled by user preference
All dimens should be references from resources.

@ShowmaxDevs
Lifecycles - here comes the pain
● Activities and Fragments are subject to lifecycles
● You are not creating them, they are created by system (you
are just creating Intent and asking system to create it or
submit Fragment transaction to FragmentManager) and you
are just being given callbacks

@ShowmaxDevs
Lifecycles activity / fragment
Hint: print these out if you are going
for Android developer interview ;-)

@ShowmaxDevs
Lifecycles - take away
● Activities and Fragments may disappear as system see fit
● When they are in background, system may kill them
● During configuration changes like orientation change/rotation they are
recreated
● You really cannot depend they live
● They give you chance to save your state and restore it, but
that’s pretty much boiler plate and you don’t want to do it

@ShowmaxDevs
ViewModels to the rescue
Activity
Fragment
View
ViewModel
state: LiveData
survives configuration changes
Your business
logic updates
state
click!
UI logic
Fragment observes
LiveData state from
viewModel
DUMB!

@ShowmaxDevs
ViewModels - more info
● https://developer.android.com/topic/libraries/architecture/
viewmodel
● Avoid putting business logic to Activities/Fragments (it’s
BAD, BAD, BAD!)- treat them as dumb view layer only
responsible to update its views and send events to ViewModel

@ShowmaxDevs
Permissions
To be able to gain access to certain system features app needs to
declare permissions in AndroidManifest.xml
● like android.permission.INTERNET
● dangerous permissions you need to ask user to give you that
permission like LOCATION, RECORD_AUDIO,
READ_CONTACTS,...

@ShowmaxDevs
REST API - Retrofit
● Library for REST API communication
● Industry standard, otherwise a lot of boilerplate code and
manual parsing (no fun)
● 1. Create data objects
● 2. Define interface
● 3. Create Retrofit client with configured converter using
selected deserializer (preferably JSON, possibly XML and
more)
https://square.github.io/retrofit/
interface ShowmaxApi {
@GET("catalogue/search")
suspend fun search(@Query("q") query: String): SearchResponse
}

@ShowmaxDevs
Retrofit - usage
● Network calls (and possibly other long running tasks) needs
to happen on background thread
● Retrofit can generate suspend functions, which you can
launch in coroutine scope with viewModel support

@ShowmaxDevs
Displaying results - RecyclerView
● Used to display lists & grids
● You need to create Adapter

@ShowmaxDevs
Image loading
● ImageView is your go to View for displaying images
● No native remote URL displaying capability
● Image Loading libraries:
● Glide (that’s what we use)
● Picasso
● Fresco (from Facebook)
● Coil (Kotlin first library)
● ...

@ShowmaxDevs
Further improvements
● Introduce Dependency Injection
● Apply obfuscation to your release builds
● buildTypes (debug/release) /productFlavors
(staging/production) if needed
● Publish on Google Play store
PROFIT!

@ShowmaxDevs
Thank you - Q&A
Contact me:
michal.ursiny@showmax.com
Twitter: @ursimon

Android crash course

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