Kotlin Android Tutorial

Content

This is a tutorial project to show how to setup and use Kotlin in Android Project. I have recently started going to the gym, and I found out that it would be easier if I had application to assist me. I am calling this application 'Workout'.

Work on this application goes in steps, each step either integrates some new functionality or demonstrates usage of specific feature of Kotlin Language.

Each step has its own tag (name in the round brackets), and a corresponding video on Youtube.

1 Project Setup (project-setup)

https://youtu.be/zfmT8fVlMhY

• Creating new Project in Android Studio
• Initialising GIT

2 Kotlin Integration (kotlin-integration)

https://youtu.be/8HuBoPYb0gw

• Adding Kotlin plugins to build.gradle
• Converting Java Code into Kotlin Code

3 Kotlin View Injections (view-injections)

https://youtu.be/cs4YZg3P4Ik

• Adding Kotlin Android Extensions Plugin
  apply plugin: 'kotlin-android-extensions'
• Using auto-generated properties for views in View Class (Activity)
  import kotlinx.android.synthetic.main.home.*

4 Anko Integration (anko-integration)

https://youtu.be/SG77qTm38nw

• Code Cleanup
• Adding Anko library to the project
  compile "org.jetbrains.anko:anko:$versions.anko"
• Examples of one line functions (Kotlin introduces specific syntax)
  fun isThisAJoke() = "NO Its not a Joke"

5 Splash Screen (splash-screen)

https://youtu.be/kUI1LRmPCBo

• Adding Anko Design library to the project
  compile "org.jetbrains.anko:anko-design:$versions.anko"
• Examples of Anko usage:
  snackbar
doAsync
uiThread
startActivity<HomeActivity>()

6 Splash Screen according to Google Guidelines (google-splash)

https://youtu.be/r9KPvkAk0BM

• Implementation of Splash Screen to enhance User Experience
• Based on: https://www.bignerdranch.com/blog/splash-screens-the-right-way/

7 Dagger Integration (dagger-integration)

https://youtu.be/F0OwtSrhh0o

• Integration of dagger into Android Kotlin Project.
• Creation and usage of 'Extension Function'
  fun AppCompatActivity.component() : ApplicationComponent = (application as Application).component
• Creation and usage of 'Extension Property'
  val AppCompatActivity.component: ApplicationComponent get() = (application as Application).component

8 Counter Initial (counter-initial)

https://youtu.be/v7pe5JN_eLs

• Using CountDownTimer for executing task after interval.
• Introduction to 'val' property
  val name: String = "tomasz"
• Introduction to 'var' property
  @Inject lateinit var context: Context
• Introduction to anonymous class in kotlin
  val timer = object : CountDownTimer(...

9 Lateinit, Nullability (lateinit-nullability)

https://youtu.be/0N72ZisrwSE

• Lateinit var property
  lateinit var onFinishFunction: () -> Unit)
• Nullability in practice
  private var onFinishFunction: (() -> Unit)? = null
• Function/Lambda as a property
  lateinit var onTickFunction: (Long) -> Unit
• Function/Lambda as a method argument
  fun onFinish(onFinishFunction: () -> Unit) {
• Invocation of Function/Lambda
  onFinishFunction.invoke()
onFinishFunction()

10 Dagger Injections, Val Property (dagger-val-property)

https://youtu.be/DXamJSAHyGQ

• Adding new Dagger Module
• Initializing component with two Modules
• Creating Singleton object in Module
• Val Property Lazy Initialization
  private val ringtone by lazy {
RingtoneManager.getRingtone(context, RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION))
}
• Val Property with Getter
  private val flags: Int
get() = PowerManager.SCREEN_BRIGHT_WAKE_LOCK or PowerManager.ACQUIRE_CAUSES_WAKEUP

11 Method with Default Arguments (default-arguments-method)

https://youtu.be/mbXjX3xeOL0

• Method with Default Arguments
  fun replaceFragment(fragment: Fragment, tag: String = fragment.javaClass.name, addToBackStack: Boolean = false) {
• Constructor with Default Arguments
  class ContentFragmentManager(private val activity: FragmentActivity, private val contentLayoutId: Int = R.id.contentFrame) {
• Showing Fragment inside Activity
• Creating ContentFragmentManager to replace fragments in FrameLayout

12 Abstract Property, Open Modifier (abstract-open-property)

https://youtu.be/W08I-X7fWVw

• Creating BaseFragment
• Creating Abstract Property
  protected abstract val layoutResourceId: Int
• Creating Open Property
  open protected val menuResourceId: Int? = null
• Making 'Java Virtual method' final
  final override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?)

13 Custom Property Setter (custom-property-setter)

https://youtu.be/xyzYjlaSkAs

• Creating Custom Property Setter
  var delegate: Delegate? = null
set(value) {
field = value
notifyStateChanged()
}
• Creating Data Model
• Creating Data Manager

14 String Templates (string-templates)

https://youtu.be/jM3YmULqUcQ

• String Template with value
  timerText.text = "$value"
• String Template with expression
  seriesNumberText.text = "${exerciseDataManager.exerciseData.seriesNumber}"

15 Elvis Operator, Equality (elvis-operator-equality)

https://youtu.be/Wn9-JarDvok

• Using Elvis Operator
  fragmentManager.fragments.firstOrNull { it?.isVisible ?: false }
• Using equality '==' sign correctly
  if (currentFragment?.javaClass != fragment.javaClass) {

16 Dagger Subcomponent, Custom Scope (dagger-subcomponent)

https://youtu.be/xRRRujQly-0

• Creating Dagger Module for specific Activity
• Creating Dagger Subcomponent
  @Subcomponent(modules = arrayOf(ExerciseModule::class))
• Creating Custom Scope to be used by Subcomponent
  annotation class ActivityScope

17 Anko Alert Dialog (anko-alert-dialog)

https://youtu.be/qOxt4xOas2M

• Creating Alert Dialog using Anko Library

Useful links

[Kotlin.org] (https://kotlinlang.org/)

[Kotlink.Anko] (https://github.com/Kotlin/anko/)

[Dagger] (https://github.com/google/dagger)

Developed By

Tomasz Morcinek
tomasz.morcinek@gmail.com
tomasz.morcinek.dev@gmail.com

License

You are free to do whatever you want with it.