How to avoid blocking of scrolling itself when using setNestedScrollingEnabled(false)?

Question

Background

We have quite a complex layout that has CollapsingToolbarLayout in it, together with a RecyclerView at the bottom.

In certain cases, we tempora

Answer 1

I want to present a nice alternative, mainly based on the one here :

AppBarLayoutEx.kt

class AppBarLayoutEx : AppBarLayout {
    private var isAppBarExpanded = true
    private val behavior = AppBarLayoutBehavior()
    private var onStateChangedListener: (Boolean) -> Unit = {}
    var enableExpandAndCollapseByDraggingToolbar: Boolean
        get() = behavior.canDrag
        set(value) {
            behavior.canDrag = value
        }

    var enableExpandAndCollapseByDraggingContent: Boolean
        get() = behavior.acceptsNestedScroll
        set(value) {
            behavior.acceptsNestedScroll = value
        }

    constructor(context: Context) : super(context)
    constructor(context: Context, attrs: AttributeSet) : super(context, attrs)

    init {
        addOnOffsetChangedListener(
                AppBarLayout.OnOffsetChangedListener { _, verticalOffset ->
                    isAppBarExpanded = verticalOffset == 0
                    onStateChangedListener(isAppBarExpanded)
                })
    }

    override fun setLayoutParams(params: ViewGroup.LayoutParams?) {
        super.setLayoutParams(params)
        (params as CoordinatorLayout.LayoutParams).behavior = behavior
    }

    fun toggleExpandedState() {
        setExpanded(!isAppBarExpanded, true)
    }

    fun setOnExpandAndCollapseListener(onStateChangedListener: (Boolean) -> Unit) {
        this.onStateChangedListener = onStateChangedListener
    }

    private class AppBarLayoutBehavior : AppBarLayout.Behavior() {
        var canDrag = true
        var acceptsNestedScroll = true

        init {
            setDragCallback(object : AppBarLayout.Behavior.DragCallback() {
                override fun canDrag(appBarLayout: AppBarLayout) = canDrag
            })
        }

        override fun onStartNestedScroll(parent: CoordinatorLayout, child: AppBarLayout, directTargetChild: View,
                                         target: View, nestedScrollAxes: Int, type: Int) = acceptsNestedScroll
    }
}

Usage: besides using it in the layout XML file, you can disable/enable the expanding of it using:

appBarLayout.enableExpandAndCollapseByDraggingToolbar = true/false

appBarLayout.enableExpandAndCollapseByDraggingContent = true/false