EmmanuelGuther

private Object increaseVersionCode() {
    Properties versionProps = new Properties()
    def versionPropsFile = file('version.properties')
    if (versionPropsFile.exists())
        versionProps.load(new FileInputStream(versionPropsFile))
    def code = (versionProps['VERSION_CODE'] ?: "410").toInteger() + 1
    versionProps['VERSION_CODE'] = code.toString()
    versionProps.store(versionPropsFile.newWriter(), null)
    return code
}

EmmanuelGuther

/** USAGE -> ('a'..'z').randomString(6) */
fun ClosedRange<Char>.randomString(lenght: Int) =
        (1..lenght)
                .map { (Random().nextInt(endInclusive.toInt() - start.toInt()) + start.toInt()).toChar() }
                .joinToString("")

EmmanuelGuther

fun generateRandomLocationInsideRadius(x0: Double, y0: Double, radius: Int): LatLng {
    val random = Random()
    // Convert radius from meters to degrees
    val radiusInDegrees = (radius / 111000f).toDouble()
    val u = random.nextDouble()
    val v = random.nextDouble()
    val w = radiusInDegrees * sqrt(u)
    val t = 2.0 * Math.PI * v
    val x = w * cos(t)
    val y = w * sin(t)

EmmanuelGuther

fun TextView.afterTextChangedDelayed(afterTextChanged: (String) -> Unit) {
    this.addTextChangedListener(object : TextWatcher {
        var timer: CountDownTimer? = null

        override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
        }

        override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
        }

EmmanuelGuther

fun TextView.showCountIncrementAnimation(from: Int? = 0, to: Int?) {
    var duration: Long? = null
    val animator = ValueAnimator()
    animator.setObjectValues(from, to)// here you set the range, from 0 to "count" value
    animator.addUpdateListener { animation -> this.text = animation.animatedValue.toString() }
    duration = when (to) {
        in 0..4 -> 200
        in 5..10 -> 1000
        in 11..50 -> 3000
        else -> 2000

EmmanuelGuther

Elvis Operator
When we have a nullable reference r, we can say "if r is not null, use it, otherwise use some non-null value x":

val l: Int = if (b != null) b.length else -1
Along with the complete if-expression, this can be expressed with the Elvis operator, written ?::

val l = b?.length ?: -1
If the expression to the left of ?: is not null, the elvis operator returns it, otherwise it returns the expression to the right. Note that the right-hand side expression is evaluated only if the left-hand side is null.

Note that, since throw and return are expressions in Kotlin, they can also be used on the right hand side of the elvis operator. This can be very handy, for example, for checking function arguments:

EmmanuelGuther

/** A viewpager with possibilities of being blocked the swipe */
class BViewPager(context: Context, attrs: AttributeSet) : ViewPager(context, attrs) {

    private var enabledSwipe: Boolean = false

    init {
        this.enabledSwipe = true
    }

    override fun onTouchEvent(event: MotionEvent): Boolean = when {

EmmanuelGuther

class LuhnValidator {
    fun isValid(cardNumber: String): Boolean {
        var s1 = 0
        var s2 = 0
        val reverse = StringBuffer(cardNumber).reverse().toString()
        for (i in reverse.indices) {
            val digit = Character.digit(reverse[i], 10)
            when {
                i % 2 == 0 -> s1 += digit
                else -> {

EmmanuelGuther

const val CARD_NUMBER_SEPARATOR = " "
const val CARD_DATE_SEPARATOR = "/"

fun EditText.creditCardNumberFormatter(afterTextChanged: (String) -> Unit) {
    var count = 0

    this.addTextChangedListener(object : TextWatcher {
        override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
        }

EmmanuelGuther

/**
 * A lifecycle-aware observable that sends only new updates after subscription, used for events like
 * navigation and Snackbar messages.
 *
 *
 * This avoids a common problem with events: on configuration change (like rotation) an update
 * can be emitted if the observer is active. This LiveData only calls the observable if there's an
 * explicit call to setValue() or call().
 *
 *