使用RecyclerView的自定义NestedScrollingParent不会丢失

Question

我创建了一个实现NestedScrollingParent的LinearLayout，然后在其中放置了一些视图（ImageView，View，RecyclerView），但是fling操作有一些问题。 视频：https://youtu.be/3liTZtKKcew

 <com.lsl.md.nested.MyNestedLinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <ImageView
            android:id="@+id/imageView"
            android:layout_width="match_parent"
            android:layout_height="300dp"
            android:scaleType="centerCrop"
            android:src="@mipmap/material_flat" />

        <View
            android:layout_width="match_parent"
            android:layout_height="48dp"
            android:background="@color/colorPrimary" />


        <android.support.v7.widget.RecyclerView
            android:id="@+id/recycler_view"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:background="@color/colorAccent" />

    </com.lsl.md.nested.MyNestedLinearLayout>

这里我创建了一个扩展LinearLayout并实现NestedScrollingParent的类，问题是当惯性滑动到RecyclerView的顶部时，上面的ImageView没有响应滑动

public class MyNestedLinearLayout extends LinearLayout implements NestedScrollingParent {
    private static final String TAG = "MyNestedLinearLayout";
    private NestedScrollingParentHelper parentHelper;
    private ImageView imageView;
    private int imageHeight;

    private OverScroller mScroller;

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

    public MyNestedLinearLayout(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public MyNestedLinearLayout(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        parentHelper = new NestedScrollingParentHelper(this);
        mScroller = new OverScroller(context);
    }


    /*NestedScrollingParent*/
    @Override
    public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
//        return target instanceof RecyclerView;
        return (nestedScrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0;
    }

    @Override
    public void onNestedScrollAccepted(View child, View target, int nestedScrollAxes) {
        Log.i(TAG, "onNestedScrollAccepted: ...");
        parentHelper.onNestedScrollAccepted(child, target, nestedScrollAxes);
    }

    @Override
    public void onStopNestedScroll(View target) {
        Log.i(TAG, "onStopNestedScroll: ...");
        parentHelper.onStopNestedScroll(target);
    }

    @Override
    public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
        Log.i(TAG, "onNestedScroll: ...");
    }

    @Override
    public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
        if (dy > 0) {
            if (getScrollY() < imageHeight) {
                scrollBy(0, dy);
                consumed[1] = dy;
            }
        }
        if (dy < 0 && !ViewCompat.canScrollVertically(target, -1)) {
            if (getScrollY() > 0) {
                scrollBy(0, dy);
                consumed[1] = dy;
            }
        }
        Log.i(TAG, "onNestedPreScroll: ...dy:");

    }

    @Override
    public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) {
        Log.i(TAG, "onNestedFling: ..." + velocityY);

        return false;
    }

    @Override
    public boolean onNestedPreFling(View target, float velocityX, float velocityY) {
        if (getScrollY() >= imageHeight) return false;
        fling((int) velocityY);
        return true;
    }

    @Override
    public int getNestedScrollAxes() {
        Log.i(TAG, "getNestedScrollAxes: ...");
        return parentHelper.getNestedScrollAxes();
    }

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
        imageView = (ImageView) getChildAt(0);
    }

    @Override
    public void scrollTo(@Px int x, @Px int y) {
        if (y < 0) {
            y = 0;
        }
        if (y > imageHeight) {
            y = imageHeight;
        }
        super.scrollTo(x, y);

    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        imageView = (ImageView) getChildAt(0);
        measureChildWithMargins(imageView, widthMeasureSpec, 0, MeasureSpec.UNSPECIFIED, 0);
        imageHeight = imageView.getMeasuredHeight();
        super.onMeasure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(MeasureSpec.getSize(heightMeasureSpec) + imageHeight,
                MeasureSpec.EXACTLY));
    }


    public void fling(int velocityY) {
        mScroller.fling(0, getScrollY(), 0, velocityY, 0, 0, 0, imageHeight);
        invalidate();
    }

    @Override
    public void computeScroll() {
        super.computeScroll();
        if (mScroller.computeScrollOffset()) {
            scrollTo(0, mScroller.getCurrY());
            invalidate();
        }
    }
}