iOS like over scroll effect on Android

Question

I want to implement the iOS-like bounce overscroll effect in my app.

I came across this link which suggests creating a custom ScrollView. But the problem is

Answer 1

Thanks to Xaver Kapeller, I have written my solution with overriding fling and little additions, using kotlin and androidx

Add coordinator dependency

implementation "androidx.coordinatorlayout:coordinatorlayout:1.1.0"

Create a new class that extends CoordinatorLayout.Behavior

import android.content.Context
import android.util.AttributeSet
import android.view.View
import android.view.ViewGroup
import android.view.animation.AccelerateDecelerateInterpolator
import androidx.coordinatorlayout.widget.CoordinatorLayout
import androidx.core.view.ViewCompat

class OverScrollBehavior(context: Context, attributeSet: AttributeSet)
: CoordinatorLayout.Behavior() {

companion object {
    private const val OVER_SCROLL_AREA = 4
}

private var overScrollY = 0

override fun onStartNestedScroll(
    coordinatorLayout: CoordinatorLayout,
    child: View,
    directTargetChild: View,
    target: View,
    axes: Int,
    type: Int
): Boolean {
    overScrollY = 0
    return true
}

override fun onNestedScroll(
    coordinatorLayout: CoordinatorLayout,
    child: View,
    target: View,
    dxConsumed: Int,
    dyConsumed: Int,
    dxUnconsumed: Int,
    dyUnconsumed: Int,
    type: Int,
    consumed: IntArray
) {
    if (dyUnconsumed == 0) {
        return
    }

    overScrollY -= (dyUnconsumed/OVER_SCROLL_AREA)
    val group = target as ViewGroup
    val count = group.childCount
    for (i in 0 until count) {
        val view = group.getChildAt(i)
        view.translationY = overScrollY.toFloat()
    }
}

override fun onStopNestedScroll(
    coordinatorLayout: CoordinatorLayout,
    child: View,
    target: View,
    type: Int
) {
    // Smooth animate to 0 when the user stops scrolling
    moveToDefPosition(target)
}

override fun onNestedPreFling(
    coordinatorLayout: CoordinatorLayout,
    child: View,
    target: View,
    velocityX: Float,
    velocityY: Float
): Boolean {
    // Scroll view by inertia when current position equals to 0
    if (overScrollY == 0) {
        return false
    }
    // Smooth animate to 0 when user fling view
    moveToDefPosition(target)
    return true
}

private fun moveToDefPosition(target: View) {
    val group = target as ViewGroup
    val count = group.childCount
    for (i in 0 until count) {
        val view = group.getChildAt(i)
        ViewCompat.animate(view)
            .translationY(0f)
            .setInterpolator(AccelerateDecelerateInterpolator())
            .start()
    }
}

}

Create XML file with CoordinatorLayout and NestedScrollView

And don't forget to add

app:layout_behavior=".OverScrollBehavior" // Or your file name

field to your NestedScrollView XML markup