pandulapeter

enum class TransitionType {
    SIBLING, DETAIL, MODAL
}

inline fun <reified T : Fragment> FragmentManager.handleReplace(
    tag: String = T::class.java.name,
    addToBackStack: Boolean = false,
    @IdRes containerId: Int = R.id.fragment_container,
    transitionType: TransitionType? = null,
    crossinline newInstance: () -> T

pandulapeter

abstract class BaseFragment<B : ViewDataBinding, VM : BaseViewModel>(@LayoutRes private val layoutResourceId: Int) : Fragment() {

    private var realBinding: B? = null
    protected val binding: B get() = realBinding ?: throw IllegalStateException("Trying to access the binding outside of the view lifecycle.")
    protected abstract val viewModel: VM

    final override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? =
        DataBindingUtil.inflate<B>(inflater, layoutResourceId, container, false).also {
            realBinding = it
        }.root

pandulapeter

abstract class BaseFragment<B : ViewDataBinding, VM : BaseViewModel>(@LayoutRes private val layoutResourceId: Int) : Fragment() {

    protected var binding by AutoClearedValue<B>()
    protected abstract val viewModel: VM

    final override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? =
        DataBindingUtil.inflate<B>(inflater, layoutResourceId, container, false).also {
            binding = it
        }.root

pandulapeter

class AutoClearedValue<T : Any> : ReadWriteProperty<Fragment, T>, LifecycleObserver {
    private var _value: T? = null

    override fun getValue(thisRef: Fragment, property: KProperty<*>): T =
        _value ?: throw IllegalStateException("Trying to call an auto-cleared value outside of the view lifecycle.")

    override fun setValue(thisRef: Fragment, property: KProperty<*>, value: T) {
        thisRef.viewLifecycleOwner.lifecycle.removeObserver(this)
        _value = value
        thisRef.viewLifecycleOwner.lifecycle.addObserver(this)

pandulapeter

class MusicPlayerFragment : Fragment() {
    private val playlistId by lazy { arguments.playlistId }
    private val songIndex by lazy { arguments.songIndex }

    companion object {
        private var Bundle.playlistId by BundleDelegate.String("key_playlist_id")
        private var Bundle.songIndex by BundleDelegate.Int("key_song_index")

        fun newInstance(playlistId: String, songIndex: Int) = MusicPlayerFragment().apply {
            arguments = Bundle().apply {

pandulapeter

class GameActivity : AppCompatActivity() {
    private var Bundle.score by BundleDelegate.Int("key_score")
    private var score = 0

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        savedInstanceState?.let { score = it.score }
    }

    override fun onSaveInstanceState(outState: Bundle) {

pandulapeter

sealed class Screen {
    abstract val screenName: String

    object Menu : Screen() {
        override val screenName = "Menu screen"
    }

    object Leaderboard : Screen() {
        override val screenName = "Leaderboard screen"
    }

pandulapeter

class IntervalDelegate(
    var value: Int,
    val minValue: Int,
    val maxValue: Int
) : ReadWriteProperty<Any?, Int> {
    
    override fun getValue(thisRef: Any?, property: KProperty<*>) = value
    
    override fun setValue(thisRef: Any?, property: KProperty<*>, value: Int) {
        this.value = value.coerceIn(minValue, maxValue)

pandulapeter

sealed class BundleDelegate<T>(protected val key: kotlin.String) : ReadWriteProperty<Bundle, T> {

    class Int(key: kotlin.String) : BundleDelegate<kotlin.Int>(key) {

        override fun getValue(thisRef: Bundle, property: KProperty<*>) = thisRef.getInt(key)

        override fun setValue(thisRef: Bundle, property: KProperty<*>, value: kotlin.Int) = thisRef.putInt(key, value)
    }

    class String(key: kotlin.String) : BundleDelegate<kotlin.String>(key) {

pandulapeter

class SharedPrefManager(context: Context) {
    private val preferences = PreferenceManager.getDefaultSharedPreferences(context.applicationContext)
    var booleanField by PreferenceFieldDelegate.Boolean("boolean_field")
    var intField by PreferenceFieldDelegate.Int("int_field")
    var stringField by PreferenceFieldDelegate.String("string_field")

    private sealed class PreferenceFieldDelegate<T>(protected val key: kotlin.String) : ReadWriteProperty<SharedPrefManager, T> {

        class Boolean(key: kotlin.String) : PreferenceFieldDelegate<kotlin.Boolean>(key) {