Implementing NestedScrollingChild issues

Question

I was trying some examples I got for implementing NestedScrollingChild for a custom view.

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context=".MainActivity">

    <android.support.design.widget.AppBarLayout
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            android:theme="@style/AppTheme.AppBarOverlay"
            app:layout_scrollFlags="scroll|enterAlways"
            app:popupTheme="@style/AppTheme.PopupOverlay"/>

    </android.support.design.widget.AppBarLayout>

    <com.ayeauto.custom.NestedScrollingChildView
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="bottom">
        </com.ayeauto.custom.NestedScrollingChildView>

</android.support.design.widget.CoordinatorLayout>

This example works fine and I could see that the ToolBar collapses with the scrolling on NestedScrollingChildView . But if I make the following change then the scrolling on the NestedScrollingChildView has no effect ie. if I scroll over it the ToolBar not collapsing

<com.ayeauto.custom.NestedScrollingChildView
            xmlns:android="http://schemas.android.com/apk/res/android"
            android:id="@+id/viewpager"
            android:layout_width="match_parent"
            android:layout_height="300dp"
            android:layout_gravity="bottom">
            </com.ayeauto.custom.NestedScrollingChildView>

ie, if I give height a size then it is not working. I am using android support library 23.1.1

import android.content.Context;
import android.support.v4.view.GestureDetectorCompat;
import android.support.v4.view.NestedScrollingChild;
import android.support.v4.view.NestedScrollingChildHelper;
import android.support.v4.view.ViewCompat;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;


public class NestedScrollingChildView extends View implements NestedScrollingChild, GestureDetector.OnGestureListener {
    private final NestedScrollingChildHelper mNestedScrollingChildHelper;
    private GestureDetectorCompat mDetector;

    public NestedScrollingChildView(Context context) {
        this(context, null);
    }

    public NestedScrollingChildView(Context context, AttributeSet attrs) {
        this(context, null, 0);
    }

    public NestedScrollingChildView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mNestedScrollingChildHelper = new NestedScrollingChildHelper(this);
        mDetector = new GestureDetectorCompat(context, this);
        setNestedScrollingEnabled(true);
    }

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

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

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

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

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

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

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

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

    @Override
    public void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        mNestedScrollingChildHelper.onDetachedFromWindow();
    }

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

    @Override
    public boolean onTouchEvent(MotionEvent event){
        final boolean handled = mDetector.onTouchEvent(event);
        if (!handled && event.getAction() == MotionEvent.ACTION_UP) {
            stopNestedScroll();
        }
        return true;
    }

    @Override
    public boolean onDown(MotionEvent e) {
        startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL);
        return true;
    }

    @Override
    public void onShowPress(MotionEvent e) {
    }

    @Override
    public boolean onSingleTapUp(MotionEvent e) {
        return false;
    }

    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
        dispatchNestedPreScroll(0, (int) distanceY, null, null);
        dispatchNestedScroll(0, 0, 0, 0, null);
        return true;
    }

    @Override
    public void onLongPress(MotionEvent e) {

    }

    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        return true;
    }
}

I got the code from here It uses android support library 22.2.1, I changed to 23.1.1 because I face this issue for a custom view I created which was working in 22.2.1 but stop working in 23.1.1