伪顶部悬浮，最简单的方式scrollview嵌套recycleView，悬浮+翻页效果

仅需自定义scrollView即可实现。

@Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
    super.onScrollChanged(l, t, oldl, oldt);
    mT = t;

    Log.i(TAG, "onScrollChanged: t:" + t + "-----oldt:" + oldt + "----getHeight-" + getHeight());
    if (t < oldt && isDown) {
        if (mT < getHeight() - 1) {
            smoothScrollToPrePage();
        }
    }
}

@Override
public boolean onTouchEvent(MotionEvent ev) {
    switch (ev.getAction()) {
        case MotionEvent.ACTION_DOWN:
            break;
        case MotionEvent.ACTION_MOVE:

            break;
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_CANCEL:
            if (!isDown) {
                if (mT > getHeight() / 8) {
                    smoothScrollToNextPage();
                } else {
                    smoothScrollToPrePage();
                }
            }

            return true;
    }
    return super.onTouchEvent(ev);
}

private boolean isDown = false;

private void smoothScrollToNextPage() {
    smoothScrollTo(0, 10000);
    Log.i(TAG, "smoothScrollToNextPage: getY" + getY() + "---getHeight" + getHeight() + "---getHeight" + getHeight());
    isDown = true;
}

private void smoothScrollToPrePage() {
    smoothScrollTo(0, 0);
    Log.i(TAG, "smoothScrollToPrePage: getY" + getY() + "---getHeight" + getHeight() + "---getHeight" + getHeight());
    isDown = false;
}

@Override
public boolean onInterceptTouchEvent(MotionEvent e) {
    int action = e.getAction();
    switch (action) {
        case MotionEvent.ACTION_DOWN:
            downY = (int) e.getRawY();
            break;
        case MotionEvent.ACTION_MOVE:
            int moveY = (int) e.getRawY();
            if (isDown) {
                if (Math.abs(moveY - downY) < mTouchSlop) {
                    return false;
                }
            } else {
                if (Math.abs(moveY - downY) > mTouchSlop) {
                    return true;
                }
            }
    }
    return super.onInterceptTouchEvent(e);
}