RecyclerView中嵌套RecycleView導致自動跳到頁面頂部或者中間的問題

在最外層RecyclerView 佈局文件中設置

android:descendantFocusability="blocksDescendants"

解釋一下：
在ViewGroup中有方法如下

/**
     * This view will get focus before any of its descendants.
     */
    public static final int FOCUS_BEFORE_DESCENDANTS = 0x20000;

    /**
     * This view will get focus only if none of its descendants want it.
     */
    public static final int FOCUS_AFTER_DESCENDANTS = 0x40000;

    /**
     * This view will block any of its descendants from getting focus, even
     * if they are focusable.
     */
    public static final int FOCUS_BLOCK_DESCENDANTS = 0x60000;

/**
     * Set the descendant focusability of this view group. This defines the relationship
     * between this view group and its descendants when looking for a view to
     * take focus in {@link #requestFocus(int, android.graphics.Rect)}.
     *
     * @param focusability one of {@link #FOCUS_BEFORE_DESCENDANTS}, {@link #FOCUS_AFTER_DESCENDANTS},
     *   {@link #FOCUS_BLOCK_DESCENDANTS}.
     */
  public void setDescendantFocusability(int focusability) {
        switch (focusability) {
            case FOCUS_BEFORE_DESCENDANTS:
            case FOCUS_AFTER_DESCENDANTS:
            case FOCUS_BLOCK_DESCENDANTS:
                break;
            default:
                throw new IllegalArgumentException("must be one of FOCUS_BEFORE_DESCENDANTS, "
                        + "FOCUS_AFTER_DESCENDANTS, FOCUS_BLOCK_DESCENDANTS");
        }
        mGroupFlags &= ~FLAG_MASK_FOCUSABILITY;
        mGroupFlags |= (focusability & FLAG_MASK_FOCUSABILITY);
    }