🖕🏻 🔃 👩🏾‍🎤 نحن نحرك RecyclerView بسهولة دون التبديل إلى ViewPager2 🧑🏽 🧖🏾 👨🏽‍💻

,
ViewPager ( ViewPager2) RecyclerView.
,
. support library 24.2.0
, ..
SnapHelper hildView
, ViewPager
. ViewPager2, , ViewPager
(ViewPager2 —
RecyclerView ,
ViewPager
api).

? . -,
RecyclerView PageTransformer
hildView (
« »). -,
ViewPager2 final,
onInterceptTouchEvent (
),
recyclerView.

,
RecyclerView ViewPager2
MotionLayout, ,
ViewPager.PageTransformer RecyclerView -
ViewPager2 .

, , :

ViewPager
sticky-
“” (BottomSheetBehavior)
—
.
? -
- " " :

ConstraintLayout
recyclerView . BottomSheetCallback
BottomSheetBehavior:

class DinosaursActivity : AppCompatActivity(), SelectorTransformListener, ItemChangeListener {

    private lateinit var bottomSheetBehavior: BottomSheetBehavior<FrameLayout>

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        setupBottomSheetBehavior()
    }

    private fun setupBottomSheetBehavior() {
        bottomSheetBehavior = BottomSheetBehavior.from(layoutBottomSheet).apply {
            state = BottomSheetBehavior.STATE_EXPANDED
            setBottomSheetCallback(object : BottomSheetBehavior.BottomSheetCallback() {
                override fun onStateChanged(bottomSheet: View, newState: Int) {}

                override fun onSlide(bottomSheet: View, offset: Float) {
                  //      
                    selector.transformation(offset)
                }
            })
        }
    }
}

transformation, “”
.

class AnimatedSelector(context: Context, attrs: AttributeSet? = null) :
    ConstraintLayout(context, attrs), SnapListener {

    constructor(context: Context) : this(context, null)

    init {
        LayoutInflater.from(context).inflate(R.layout.layout_animated_selector, this, true)
        horizontalAdapter = InfinityAdapter()
        verticalAdapter = DefaultAdapter()
        horizontalRecycler.layoutManager =
            LinearLayoutManager(context, RecyclerView.HORIZONTAL, false)
        verticalRecycler.layoutManager =
            LinearLayoutManager(context, RecyclerView.VERTICAL, false)
        horizontalRecycler.adapter = horizontalAdapter
        verticalRecycler.adapter = verticalAdapter
        }

    fun transformation(progress: Float) {
      //           
        val verticalProgress = if (progress < 0.6f) progress / 0.6f else 1f
        val horizontalProgress = 1f - (if (progress > 0.6f) (progress - 0.6f) / 0.4f else 0f)
      //        -
      }     
}

—
ViewPager.PageTransformer.

— ItemViewTransformer
transformItemView, transformPage
ViewPager.PageTransformer:

abstract class ItemViewTransformer {

   fun attachToRecycler(recycler: RecyclerView) {}

   private fun updatePositions() {}

   abstract fun transformItemView(view: View, position: Float)
}

attachToRecycler recyclerView
RecyclerView.AdapterDataObserver RecyclerView.OnScrollListener:

    fun attachToRecycler(recycler: RecyclerView) {
        check(recycler.layoutManager is LinearLayoutManager) { "Incorrect LayoutManager Type" }
        this.layoutManager = recycler.layoutManager as LinearLayoutManager
        this.recyclerView = recycler
        this.attachedAdapter = recycler.adapter as RecyclerView.Adapter<*>

        dataObserver = object : RecyclerView.AdapterDataObserver() {
            override fun onChanged() {
                updatePositions()
            }

            override fun onItemRangeChanged(positionStart: Int, itemCount: Int) {
                onChanged()
            }

            override fun onItemRangeChanged(positionStart: Int, itemCount: Int, payload: Any?) {
                onChanged()
            }

            override fun onItemRangeInserted(positionStart: Int, itemCount: Int) {
                onChanged()
            }

            override fun onItemRangeRemoved(positionStart: Int, itemCount: Int) {
                onChanged()
            }

            override fun onItemRangeMoved(fromPosition: Int, toPosition: Int, itemCount: Int) {
                onChanged()
            }
        }
        attachedAdapter.registerAdapterDataObserver(dataObserver)

        scrollListener = object : RecyclerView.OnScrollListener() {
            override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
            }

            override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
                updatePositions()
            }
        }

        recyclerView.addOnScrollListener(scrollListener)
    }

updatePosition transformItemView
childView
( childViews
/ ):

    private fun updatePositions() {
        val childCount = layoutManager.childCount
        for (i in 0 until childCount) {
            val view = layoutManager.getChildAt(i)
            view?.let {
                val position: Float = if (layoutManager.orientation == RecyclerView.HORIZONTAL) {
                    (view.left - currentFrameLeft) / (view.measuredWidth + view.marginLeft + view.marginRight)
                } else {
                    (view.top - currentFrameLeft) / (view.measuredHeight + view.marginTop + view.marginBottom)
                }
                transformItemView(view, position)
            }
        }
    }

, , ,
pageTransformer, - ,
recyclerView.

3. Sticky-

sticky-
.
:

class BouncingTransformer(currentItemViewOffset: Int) : ItemViewTransformer(currentItemViewOffset) {
    override fun transformItemView(view: View, position: Float) {
        when {
            position > -1f && position < 0 -> {
                view.scaleX = 1f
                view.scaleY = 1f
                view.translationX = 0f
            }
            position >= 0f && position < 0.5f -> {
                view.scaleY = 1f - 0.2f * position / 0.5f
                view.scaleX = 1f - 0.2f * position / 0.5f
                view.translationX = view.width * 0.4f - view.width * 0.4f * (0.5f - position) / 0.5f
            }
            position >= 0.5f && position < 1f -> {
                view.scaleY = 0.8f
                view.scaleX = 0.8f
                view.translationX = view.width * (0.9f - position)
            }
            position >= 1f && position < 2f -> {
                view.scaleY = 0.8f
                view.scaleX = 0.8f
                view.translationX = -view.width * 0.1f
            }
        }
    }
}

BouncingTransformer
recyclerView:

    LayoutInflater.from(context).inflate(R.layout.layout_animated_selector, this, true)
        horizontalAdapter = InfinityAdapter()
        horizontalRecycler.layoutManager = ScrollDisablingLayoutManager(context, RecyclerView.HORIZONTAL, false)
        horizontalRecycler.adapter = horizontalAdapter
        bouncingTransformer = BouncingTransformer(-cardShift)
                .apply { attachToRecycler(horizontalRecycler) }
    }

sticky-:

-, , , ,
ItemDecoration.

4. -

value- onUpdate:

abstract class ItemViewAnimatorUpdater {

    fun attachToRecycler(recycler: RecyclerView): ItemViewAnimatorUpdater {}

    fun update(progress: Float = 0f) {}

    abstract fun onUpdate(view: View, visiblePosition: Int, adapterPosition: Int, progress: Float)
}

attachToRecycler recyclerView:

    fun attachToRecycler(recycler: RecyclerView): ItemViewAnimatorUpdater {
        check(recycler.layoutManager is LinearLayoutManager) { "Incorrect LayoutManager Type" }
        this.layoutManager = recycler.layoutManager as LinearLayoutManager
        this.recyclerView = recycler
        return this
    }

update
:

    fun update(progress: Float = 0f) {
        val childCount = layoutManager.childCount
        for (i in 0 until childCount) {
            val view = layoutManager.getChildAt(i)
            view?.let {
                val visiblePosition = if (layoutManager.orientation == RecyclerView.HORIZONTAL) {
                    view.right.toFloat() / (view.measuredWidth + view.marginLeft + view.marginRight)
                } else {
                    view.bottom.toFloat() / (view.measuredHeight + view.marginTop + view.marginBottom)
                }
                val adapterPosition = recyclerView.getChildAdapterPosition(view)
                onUpdate(view, ceil(visiblePosition).toInt(), adapterPosition, progress)
            }
        }
    }

“” recyclerView
onUpdate:

class EmergingUpdater(private val horizontalOffset: Int, private val verticalOffset: Int) : ItemViewAnimatorUpdater() {
    override fun onUpdate(view: View, visiblePosition: Int, adapterPosition: Int, progress: Float) {
        view.translationX = progress * (visiblePosition) * horizontalOffset
        if (visiblePosition > 1) {
            view.translationY = -verticalOffset * visiblePosition + (1 - progress) * visiblePosition * verticalOffset
        }
    }
}

, ,
BottomSheetCallback. :

“”
:

class ScatterUpdater(private val leftOffset: Int, private val rightOffset: Int) : ItemViewAnimatorUpdater() {
    override fun onUpdate(view: View, visiblePosition: Int, adapterPosition: Int, progress: Float) {
        if (visiblePosition == 1) {
            view.translationX = -progress * leftOffset
        } else {
            view.translationX = progress * rightOffset - view.width * 0.1f
        }
    }
}

childView.
. ,
ItemViewAnimatorUpdater:

class SlideLeftWithExcludeUpdater(private val excludedPosition: Int, private val leftOffset: Int) : ItemViewAnimatorUpdater() {
    override fun onUpdate(view: View, visiblePosition: Int, adapterPosition: Int, progress: Float) {
        if (adapterPosition != excludedPosition) {
            view.translationX = -progress * leftOffset
        }
    }
}

ItemAnimator:

class RemoveItemAnimator(private val leftOffset: Int, private val duration: Long) : DefaultItemAnimator() {
    override fun animateRemove(holder: RecyclerView.ViewHolder): Boolean {
        val animator = ValueAnimator.ofFloat(0f, 1f)
        animator.addUpdateListener { valueAnimator ->
            holder.itemView.translationX = -(valueAnimator.animatedValue as Float) * leftOffset
        }
        animator.addListener(object : Animator.AnimatorListener {
            override fun onAnimationRepeat(p0: Animator?) {
            }

            override fun onAnimationEnd(p0: Animator?) {
                animator.removeAllListeners()
            }

            override fun onAnimationCancel(p0: Animator?) {
            }

            override fun onAnimationStart(p0: Animator?) {
            }
        })
        animator.duration = duration
        animator.start()
        return false
    }
}

class SlideRightUpdater(private val rightOffset: Int) : ItemViewAnimatorUpdater() {
    override fun onUpdate(view: View, visiblePosition: Int, adapterPosition: Int, progress: Float) {
        if (visiblePosition == 1) {
            view.translationX = 0f
        } else {
            view.translationX = progress * rightOffset - view.width * 0.1f
        }
    }
}

.
:

ViewPager, , ,
, data building
ViewPager.PageTransformer —
RecyclerView — ,
, ItemAtimator, ItemDecoration
.

, . !

نحن نحرك RecyclerView بسهولة دون التبديل إلى ViewPager2

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