Extension for BottomSheet.BottomSheetBehavior which invokes an function when sheet is collapsed, this can be useful is the sheet need to display new data

BottomSheetExt.kt

/**
 * Call to populate new data for Bottomsheet.
 * If Bottomsheet is shown it will collapse first, then it will invoke doWhenCollapsed
 */
inline fun <reified T : View> BottomSheetBehavior<T>.colapseAndShow(noinline doWhenCollapsed: () -> Unit) {
    when (state) {
        STATE_EXPANDED,
        STATE_HALF_EXPANDED -> {
            addBottomSheetCallback(WaitForCollapsedState(this, doWhenCollapsed))
            return // don't change state again for following conditions
        }
        STATE_COLLAPSED,
        STATE_HIDDEN -> {
            doWhenCollapsed()
            state = BottomSheetBehavior.STATE_EXPANDED
            return
        }
    }
}

/**
 * Callback handler which waits until sheet is collapsed to invoke function
 */
class WaitForCollapsedState<T : View>(
    private val bottomSheet: BottomSheetBehavior<T>,
    private val doWhenCollapsed: () -> Unit
) :
    BottomSheetBehavior.BottomSheetCallback() {

    init {
        bottomSheet.state = STATE_COLLAPSED
    }

    override fun onSlide(bottomSheet: View, slideOffset: Float) {
        // ignore
    }

    override fun onStateChanged(view: View, newState: Int) {
        when (newState) {
            STATE_EXPANDED,
            STATE_HALF_EXPANDED,
            STATE_HIDDEN,
            STATE_DRAGGING,
            STATE_SETTLING -> {
                // do nothing
            }
            STATE_COLLAPSED -> {
                bottomSheet.removeBottomSheetCallback(this)
                doWhenCollapsed()
            }
        }
    }

}