模仿京东-上下左右滑动冲突

android:layout_width="match_parent"
android:layout_height="wrap_content"

public class NestedScrollLayout extends NestedScrollView {
    private View topView; //头部的View
    private ViewGroup contentView; // ViewPager中的ReyclerView
    private static final String TAG = "NestedScrollLayout"; //TAG

    public NestedScrollLayout(Context context) {
        this(context, null);
        init();
    }

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

    public NestedScrollLayout(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        this(context, attrs, defStyleAttr, 0);
        init();
    }

    public NestedScrollLayout(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private FlingHelper mFlingHelper; // veltociy和distance的转换

    int totalDy = 0;
    /**
     * 用于判断RecyclerView是否在fling
     */
    boolean isStartFling = false;
    /**
     * 记录当前滑动的y轴加速度
     */
    private int velocityY = 0;

    private void init() {
        mFlingHelper = new FlingHelper(getContext());
        setOnScrollChangeListener(new View.OnScrollChangeListener() { //监听自己（NestedScrollView）滑动
            @Override
            public void onScrollChange(View v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {
                if (isStartFling) {
                    totalDy = 0;
                    isStartFling = false;
                }
                if (scrollY == 0) { // 到达顶部的时候
                    Log.i(TAG, "TOP SCROLL");
                   // refreshLayout.setEnabled(true);
                }
                // topView完全消失了，该子View处理了
                if (scrollY == (getChildAt(0).getMeasuredHeight() - v.getMeasuredHeight())) {
                    Log.i(TAG, "BOTTOM SCROLL");
                    dispatchChildFling();
                }
                //在RecyclerView fling情况下，记录当前RecyclerView在y轴的偏移
                totalDy += scrollY - oldScrollY;
            }
        });
    }

    private void dispatchChildFling() {
        if (velocityY != 0) { // 滑动的速度，和distance可以相互转换
            // 转换成距离
            Double splineFlingDistance = mFlingHelper.getSplineFlingDistance(velocityY);
            if (splineFlingDistance > totalDy) {
                // 转换成velocityY
                childFling(mFlingHelper.getVelocityByDistance(splineFlingDistance - Double.valueOf(totalDy)));
            }
        }
        // 处理完之后，恢复默认值
        totalDy = 0;
        velocityY = 0;
    }

    private void childFling(int velY) {
        RecyclerView childRecyclerView = getChildRecyclerView(contentView); // 找到子View（RecyclerView）
        if (childRecyclerView != null) {
            childRecyclerView.fling(0, velY); //fling事件传出去
        }
    }

    @Override
    public void fling(int velocityY) { // 自己的fling
        super.fling(velocityY);
        if (velocityY  0 && getScrollY() 

public class FlingHelper {
    private static float DECELERATION_RATE = ((float) (Math.log(0.78d) / Math.log(0.9d)));
    private static float mFlingFriction = ViewConfiguration.getScrollFriction();
    private static float mPhysicalCoeff;

    public FlingHelper(Context context) {
        mPhysicalCoeff = context.getResources().getDisplayMetrics().density * 160.0f * 386.0878f * 0.84f;
    }

    private double getSplineDeceleration(int i) {
        return Math.log((double) ((0.35f * ((float) Math.abs(i))) / (mFlingFriction * mPhysicalCoeff)));
    }

    private double getSplineDecelerationByDistance(double d) {
        return ((((double) DECELERATION_RATE) - 1.0d) * Math.log(d / ((double) (mFlingFriction * mPhysicalCoeff)))) / ((double) DECELERATION_RATE);
    }

    public double getSplineFlingDistance(int i) {
        return Math.exp(getSplineDeceleration(i) * (((double) DECELERATION_RATE) / (((double) DECELERATION_RATE) - 1.0d))) * ((double) (mFlingFriction * mPhysicalCoeff));
    }

    public int getVelocityByDistance(double d) {
        return Math.abs((int) (((Math.exp(getSplineDecelerationByDistance(d)) * ((double) mFlingFriction)) * ((double) mPhysicalCoeff)) / 0.3499999940395355d));
    }
}