Data binding tracking

DataBindingTrackingExample.kt

inline fun <V : View, I> V.trackInstance(
    newInstance: I?,
    @IdRes instanceResId: Int,
    onDetached: V.(I) -> Unit = {},
    onAttached: V.(I) -> Unit = {}
) {
    ListenerUtil.trackListener(this, newInstance, instanceResId).let { oldInstance ->
        if (oldInstance !== newInstance) { // referential comparison
            oldInstance?.let { onDetached(oldInstance) }
            newInstance?.let { onAttached(newInstance) }
        }
    }
}

// trackInstance example with DefaultTimeBar from ExoPlayer:

// can't use kotlin Function1 as it's generic :'(
interface LongBindingConsumer {
    fun invoke(value: Long)
}

// no inverse binding here as there's no way to get the position like SeekBar
@BindingAdapter(
    "onScrubStart",
    "onScrubMove",
    "onScrubStop", requireAll = false
)
fun DefaultTimeBar.bind(
    onScrubStart: LongBindingConsumer?,
    onScrubMove: LongBindingConsumer?,
    onScrubStop: LongBindingConsumer?
) {
    trackInstance(
        newInstance = if (onScrubStart != null || onScrubMove != null || onScrubStop != null) {
            object : TimeBar.OnScrubListener {
                override fun onScrubStart(timeBar: TimeBar?, position: Long) {
                    onScrubStart?.invoke(position)
                }

                override fun onScrubMove(timeBar: TimeBar?, position: Long) {
                    onScrubMove?.invoke(position)
                }

                override fun onScrubStop(timeBar: TimeBar?, position: Long, canceled: Boolean) {
                    onScrubStop?.invoke(position)
                }
            }
        } else null,
        instanceResId = R.id.timebar_on_scrub_listener, // create ID for everything you want to track
        onDetached = { removeListener(it) },
        onAttached = { addListener(it) }
    )
}