<android.support.v7.widget.RecyclerViewandroid:id="@+id/recycler_view"android:layout_width="match_parent"android:layout_height="match_parent"app:layout_behavior="@string/appbar_scrolling_view_behavior"/>當RecyclerView外面再加一層 SwipeRefreshLayout的時候app:layout_behavior="@string/appbar_scrolling_view_behavior"這句話為什么要放到上一層？變成這樣：<android.support.v4.widget.SwipeRefreshLayoutandroid:id="@+id/swipe_refresh"android:layout_width="match_parent"android:layout_height="match_parent"app:layout_behavior="@string/appbar_scrolling_view_behavior"><android.support.v7.widget.RecyclerViewandroid:id="@+id/recycler_view"android:layout_width="match_parent"android:layout_height="match_parent" /></android.support.v4.widget.SwipeRefreshLayout>為什么要把app:layout_behavior="@string/appbar_scrolling_view_behavior"放到上一層呢？