jacobmoncur

class App: Application() {
    companion object {
        lateinit var database: MyDatabase
    }
    override fun onCreate() {
        super.onCreate()
        App.database =  Room.databaseBuilder(this, MyDatabase::class.java, "my-database").build()

    }
}

jacobmoncur

Kotlin! (kotlinlang.org)


// Kotlin is...
// A Statically typed programming language
// for the JVM,
// Android
// and the browser

jacobmoncur

class Cacheable<T>(val key: String, val default: T, val valueSet: (value: T) -> Unit = {})  {
    val type: Type = object : TypeToken<T>(){}.type
    var value: T by Delegates.observable(default) { prop, old, new ->
        new?.let { valueSet(it) }
    }

    operator fun getValue(thisRef: Any?, property: KProperty<*>): T {
        if(value == null) { value = Cacher.getFromCache(key, default, type) }
        return value ?: default

jacobmoncur

Variables

val firstName: String = "Luke"

val lastName = "Skywalker" // `String` type is inferred


val immutableInt = 20 // `val` is immutable

jacobmoncur

Nullable

// Optional listener
listenerInterface?.notifyOfSomething()


// `elvis operator` ?: allows for default value
val likeCount = comment?.likes ?: 0

jacobmoncur

Delegated Properties

class Example {
    var p: String by Delegate()
}


class Delegate {
    operator fun getValue(refr: Any?, prop: KProperty<*>): String {

jacobmoncur

When

when(currentButtonState){
    ButtonState.GONE -> setupGoneButton(duration)
    ButtonState.BEGIN -> setupStartButton(duration)
    ButtonState.PROGRESS -> setupProgress()
    ButtonState.SUCCESS -> setupSuccessButton()
}

jacobmoncur

Extension Functions

Animator anim = ObjectAnimator.ofFloat(mainView, "translationY", 500.f);
anim.setInterpolator(new AccelerateDecelerateInterpolator());
anim.setDuration(300);
anim.setStartDelay(100);

Animator anim1 = ObjectAnimator.ofFloat(otherView, "translationY", 200.f);
anim1.setInterpolator(new AccelerateDecelerateInterpolator());

jacobmoncur

val snapshot = try {
    cache[key] ?: return null
} catch (e: IOException) {
    // Give up because the cache cannot be read.
      return null
}

jacobmoncur

Lambdas

button.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        doSomethingAmazing();
    }
});