Nested Scrolling Layout

NestedScrollCoordinatorLayout.java

import android.content.Context;
import android.support.annotation.Nullable;
import android.support.design.widget.CoordinatorLayout;
import android.support.v4.view.NestedScrollingChild2;
import android.support.v4.view.NestedScrollingChildHelper;
import android.support.v4.view.ViewCompat;
import android.util.AttributeSet;
import android.view.View;

public class NestedScrollCoordinatorLayout extends CoordinatorLayout implements NestedScrollingChild2 {

    private NestedScrollingChildHelper mChildHelper;

    public NestedScrollCoordinatorLayout(Context context) {
        super(context);
        mChildHelper = new NestedScrollingChildHelper(this);
        setNestedScrollingEnabled(true);
    }

    public NestedScrollCoordinatorLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        mChildHelper = new NestedScrollingChildHelper(this);
        setNestedScrollingEnabled(true);
    }

    public NestedScrollCoordinatorLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mChildHelper = new NestedScrollingChildHelper(this);
        setNestedScrollingEnabled(true);
    }

    @Override
    public boolean isNestedScrollingEnabled() {
        return mChildHelper.isNestedScrollingEnabled();
    }

    @Override
    public void setNestedScrollingEnabled(boolean enabled) {
        mChildHelper.setNestedScrollingEnabled(enabled);
    }

    @Override
    public boolean hasNestedScrollingParent() {
        return mChildHelper.hasNestedScrollingParent();
    }

    @Override
    public boolean hasNestedScrollingParent(int type) {
        return mChildHelper.hasNestedScrollingParent(type);
    }

    @Override
    public boolean onStartNestedScroll(View child, View target, int axes, int type) {
        boolean superResult = super.onStartNestedScroll(child, target, axes, type);
        return startNestedScroll(axes, type) || superResult;
    }

    @Override
    public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
        boolean superResult = super.onStartNestedScroll(child, target, nestedScrollAxes);
        return startNestedScroll(nestedScrollAxes) || superResult;
    }

    @Override
    public void onNestedPreScroll(View target, int dx, int dy, int[] consumed, int type) {
        dispatchNestedPreScroll(dx, dy, consumed, null, type);
        if (consumed[1] == 0) {
            super.onNestedPreScroll(target, dx, dy, consumed, type);
        }
    }

    @Override
    public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
        dispatchNestedPreScroll(dx, dy, consumed, null);
        if (consumed[1] == 0) {
            super.onNestedPreScroll(target, dx, dy, consumed, ViewCompat.TYPE_TOUCH);
        }
    }

    @Override
    public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int type) {
        super.onNestedScroll(target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, type);
        dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, null, type);
    }

    @Override
    public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
        super.onNestedScroll(target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);
        dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, null);
    }

    @Override
    public void onStopNestedScroll(View target, int type) {
        super.onStopNestedScroll(target, type);
        stopNestedScroll(type);
    }

    @Override
    public void onStopNestedScroll(View target) {
        super.onStopNestedScroll(target);
        stopNestedScroll();
    }

    @Override
    public boolean onNestedPreFling(View target, float velocityX, float velocityY) {
        boolean superResult = super.onNestedPreFling(target, velocityX, velocityY);
        return dispatchNestedPreFling(velocityX, velocityY) || superResult;
    }

    @Override
    public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) {
        boolean superResult = super.onNestedFling(target, velocityX, velocityY, consumed);
        return dispatchNestedFling(velocityX, velocityY, consumed) || superResult;
    }

    @Override
    public boolean startNestedScroll(int axes, int type) {
        return mChildHelper.startNestedScroll(axes, type);
    }

    @Override
    public boolean startNestedScroll(int axes) {
        return mChildHelper.startNestedScroll(axes);
    }

    @Override
    public void stopNestedScroll() {
        mChildHelper.stopNestedScroll();
    }

    @Override
    public void stopNestedScroll(int type) {
        mChildHelper.stopNestedScroll(type);
    }

    @Override
    public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, @Nullable int[] offsetInWindow, int type) {
        return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow, type);
    }

    @Override
    public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, @Nullable int[] offsetInWindow) {
        return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow);
    }

    @Override
    public boolean dispatchNestedPreScroll(int dx, int dy, @Nullable int[] consumed, @Nullable int[] offsetInWindow) {
        return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, ViewCompat.TYPE_TOUCH);
    }

    @Override
    public boolean dispatchNestedPreScroll(int dx, int dy, @Nullable int[] consumed, @Nullable int[] offsetInWindow, int type) {
        return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type);
    }

    @Override
    public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
        return mChildHelper.dispatchNestedPreFling(velocityX, velocityY);
    }

    @Override
    public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
        return mChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);
    }
}

Doesn't work when user scroll up. You have to implement NestedScrollingChild3 and method dispatchNestedScroll. It will work.
Add this:

override fun onNestedScroll(
        target: View,
        dxConsumed: Int,
        dyConsumed: Int,
        dxUnconsumed: Int,
        dyUnconsumed: Int,
        type: Int,
        consumed: IntArray
    ) {
        super.onNestedScroll(
            target,
            dxConsumed,
            dyConsumed,
            dxUnconsumed,
            dyUnconsumed,
            type,
            consumed
        )
        dispatchNestedScroll(
            dxConsumed,
            dyConsumed,
            dxUnconsumed,
            dyUnconsumed,
            null,
            type,
            consumed
        )
    }

    override fun dispatchNestedScroll(
        dxConsumed: Int,
        dyConsumed: Int,
        dxUnconsumed: Int,
        dyUnconsumed: Int,
        offsetInWindow: IntArray?,
        type: Int,
        consumed: IntArray
    ) {
        mChildHelper.dispatchNestedScroll(
            dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow, type, consumed
        )
    }

Doesn't work when user scroll up. You have to implement NestedScrollingChild3 and method dispatchNestedScroll. It will work. Add this:

override fun onNestedScroll(
        target: View,
        dxConsumed: Int,
        dyConsumed: Int,
        dxUnconsumed: Int,
        dyUnconsumed: Int,
        type: Int,
        consumed: IntArray
    ) {
        super.onNestedScroll(
            target,
            dxConsumed,
            dyConsumed,
            dxUnconsumed,
            dyUnconsumed,
            type,
            consumed
        )
        dispatchNestedScroll(
            dxConsumed,
            dyConsumed,
            dxUnconsumed,
            dyUnconsumed,
            null,
            type,
            consumed
        )
    }

    override fun dispatchNestedScroll(
        dxConsumed: Int,
        dyConsumed: Int,
        dxUnconsumed: Int,
        dyUnconsumed: Int,
        offsetInWindow: IntArray?,
        type: Int,
        consumed: IntArray
    ) {
        mChildHelper.dispatchNestedScroll(
            dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow, type, consumed
        )
    }

Thx! It was really helpful :)

This solution works, but based on my experience, it has some subtle nested scrolling bugs when there is more than one level of nesting. I spent a few days fixing it, and this seems to be the most reliable version:

class NestedScrollCoordinatorLayout @JvmOverloads constructor(
    context: Context,
    attrs: AttributeSet? = null,
    defStyleAttr: Int = 0,
) : CoordinatorLayout(context, attrs, defStyleAttr), NestedScrollingChild3 {

    private val helper = NestedScrollingChildHelper(this)

    init {
        isNestedScrollingEnabled = true
    }

    override fun onStartNestedScroll(child: View, target: View, axes: Int, type: Int): Boolean {
        val superResult = super.onStartNestedScroll(child, target, axes, type)
        return startNestedScroll(axes, type) || superResult
    }

    override fun onStartNestedScroll(child: View, target: View, axes: Int): Boolean {
        val superResult = super.onStartNestedScroll(child, target, axes)
        return startNestedScroll(axes) || superResult
    }

    override fun onNestedPreScroll(target: View, dx: Int, dy: Int, consumed: IntArray, type: Int) {
        val parentConsumed = intArrayOf(0, 0)
        val thisConsumed = intArrayOf(0, 0)
        // Dispatch the pre-scroll to the scrolling parent for it to consume first
        dispatchNestedPreScroll(dx, dy, parentConsumed, null, type)
        // Then let this view consume the rest
        super.onNestedPreScroll(
            target,
            dx - parentConsumed[0],
            dy - parentConsumed[1],
            thisConsumed,
            type,
        )
        // The final total consumed must take into account both the parent and this view's
        // consumed
        consumed[0] += thisConsumed[0] + parentConsumed[0]
        consumed[1] += thisConsumed[1] + parentConsumed[1]
    }

    override fun onNestedPreScroll(target: View, dx: Int, dy: Int, consumed: IntArray) {
        val parentConsumed = intArrayOf(0, 0)
        val thisConsumed = intArrayOf(0, 0)
        // Dispatch the pre-scroll to the scrolling parent for it to consume first
        dispatchNestedPreScroll(dx, dy, parentConsumed, null)
        // Then let this view consume the rest
        super.onNestedPreScroll(
            target,
            dx - parentConsumed[0],
            dy - parentConsumed[1],
            thisConsumed,
        )
        // The final total consumed must take into account both the parent and this view's
        // consumed
        consumed[0] += thisConsumed[0] + parentConsumed[0]
        consumed[1] += thisConsumed[1] + parentConsumed[1]
    }

    override fun onNestedScroll(
        target: View,
        dxConsumed: Int,
        dyConsumed: Int,
        dxUnconsumed: Int,
        dyUnconsumed: Int,
        type: Int,
        consumed: IntArray,
    ) {
        val parentConsumed = intArrayOf(0, 0)
        val thisConsumed = intArrayOf(0, 0)
        // Dispatch the newsted-scroll to the scrolling parent for it to consume first
        dispatchNestedScroll(
            dxConsumed,
            dyConsumed,
            dxUnconsumed,
            dyUnconsumed,
            null,
            type,
            thisConsumed,
        )
        // Then let this view consume the rest
        super.onNestedScroll(
            target,
            dxConsumed + thisConsumed[0],
            dyConsumed + thisConsumed[1],
            dxUnconsumed - thisConsumed[0],
            dyUnconsumed - thisConsumed[1],
            type,
            parentConsumed,
        )
        // The final total consumed must take into account both the parent and this view's
        // consumed
        consumed[0] += thisConsumed[0] + parentConsumed[0]
        consumed[1] += thisConsumed[1] + parentConsumed[1]
    }

    override fun onNestedScroll(
        target: View,
        dxConsumed: Int,
        dyConsumed: Int,
        dxUnconsumed: Int,
        dyUnconsumed: Int,
        type: Int,
    ) {
        dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, null, type)
        super.onNestedScroll(target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, type)
    }

    override fun onNestedScroll(
        target: View,
        dxConsumed: Int,
        dyConsumed: Int,
        dxUnconsumed: Int,
        dyUnconsumed: Int,
    ) {
        dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, null)
        super.onNestedScroll(target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed)
    }

    override fun onStopNestedScroll(target: View, type: Int) {
        super.onStopNestedScroll(target, type)
        stopNestedScroll(type)
    }

    override fun onStopNestedScroll(target: View) {
        super.onStopNestedScroll(target)
        stopNestedScroll()
    }

    override fun onNestedPreFling(target: View, velocityX: Float, velocityY: Float): Boolean {
        val superResult = super.onNestedPreFling(target, velocityX, velocityY)
        return dispatchNestedPreFling(velocityX, velocityY) || superResult
    }

    override fun onNestedFling(
        target: View,
        velocityX: Float,
        velocityY: Float,
        consumed: Boolean,
    ): Boolean {
        val superResult = super.onNestedFling(target, velocityX, velocityY, consumed)
        return dispatchNestedFling(velocityX, velocityY, consumed) || superResult
    }

    override fun isNestedScrollingEnabled(): Boolean = helper.isNestedScrollingEnabled

    override fun setNestedScrollingEnabled(enabled: Boolean) {
        helper.isNestedScrollingEnabled = enabled
    }

    override fun hasNestedScrollingParent(type: Int): Boolean =
        helper.hasNestedScrollingParent(type)

    override fun hasNestedScrollingParent(): Boolean = helper.hasNestedScrollingParent()

    override fun startNestedScroll(axes: Int, type: Int): Boolean =
        helper.startNestedScroll(axes, type)

    override fun startNestedScroll(axes: Int): Boolean = helper.startNestedScroll(axes)

    override fun stopNestedScroll(type: Int) {
        helper.stopNestedScroll(type)
    }

    override fun stopNestedScroll() {
        helper.stopNestedScroll()
    }

    override fun dispatchNestedScroll(
        dxConsumed: Int,
        dyConsumed: Int,
        dxUnconsumed: Int,
        dyUnconsumed: Int,
        offsetInWindow: IntArray?,
        type: Int,
        consumed: IntArray,
    ) {
        helper.dispatchNestedScroll(
            dxConsumed,
            dyConsumed,
            dxUnconsumed,
            dyUnconsumed,
            offsetInWindow,
            type,
            consumed,
        )
    }

    override fun dispatchNestedScroll(
        dxConsumed: Int,
        dyConsumed: Int,
        dxUnconsumed: Int,
        dyUnconsumed: Int,
        offsetInWindow: IntArray?,
        type: Int,
    ): Boolean = helper.dispatchNestedScroll(
        dxConsumed,
        dyConsumed,
        dxUnconsumed,
        dyUnconsumed,
        offsetInWindow,
        type,
    )

    override fun dispatchNestedScroll(
        dxConsumed: Int,
        dyConsumed: Int,
        dxUnconsumed: Int,
        dyUnconsumed: Int,
        offsetInWindow: IntArray?,
    ): Boolean = helper.dispatchNestedScroll(
        dxConsumed,
        dyConsumed,
        dxUnconsumed,
        dyUnconsumed,
        offsetInWindow,
    )

    override fun dispatchNestedPreScroll(
        dx: Int,
        dy: Int,
        consumed: IntArray?,
        offsetInWindow: IntArray?,
        type: Int,
    ): Boolean = helper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type)

    override fun dispatchNestedPreScroll(
        dx: Int,
        dy: Int,
        consumed: IntArray?,
        offsetInWindow: IntArray?,
    ): Boolean =
        helper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow)

    override fun dispatchNestedPreFling(velocityX: Float, velocityY: Float): Boolean =
        helper.dispatchNestedPreFling(velocityX, velocityY)

    override fun dispatchNestedFling(
        velocityX: Float,
        velocityY: Float,
        consumed: Boolean,
    ): Boolean =
        helper.dispatchNestedFling(velocityX, velocityY, consumed)
}