No adapter attached; skipping layout 原因、解决办法

    void dispatchLayout() {
        if (mAdapter == null) {
            Log.e(TAG, "No adapter attached; skipping layout");
            // leave the state in START
            return;
        }
        if (mLayout == null) {
            Log.e(TAG, "No layout manager attached; skipping layout");
            // leave the state in START
            return;
        }
        ....
      }

        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
        mRecyclerView.setLayoutManager(linearLayoutManager);

    /**
     * @param context       Current context, will be used to access resources.
     * @param orientation   Layout orientation. Should be {@link #HORIZONTAL} or {@link
     *                      #VERTICAL}.
     * @param reverseLayout When set to true, layouts from end to start.
     */
    public LinearLayoutManager(Context context, int orientation, boolean reverseLayout) {
        setOrientation(orientation);
        setReverseLayout(reverseLayout);
        setAutoMeasureEnabled(true);
    }

mRecyclerView.setLayoutManager(new LinearLayoutManager(mContext));

    /**
     * Creates a vertical LinearLayoutManager
     *
     * @param context Current context, will be used to access resources.
     */
    public LinearLayoutManager(Context context) {
        this(context, VERTICAL, false);
    }