在安卓4.4.2的關於藍牙開發的一個sample BluetoothChat中，調試時，老是出錯：Attempt to invoke virtual method 'void android.app.ActionBar.setTitle
上網查了一下，是這么說的：
（http://www.tuicool.com/articles/IRzUR3M）
The LayoutManager is probably the most interesting part of theRecyclerView . This class is responsible for layouting all child views. There isone default implementation available: LinearLayoutManager which you can use for vertical as well as horizontal lists.
You have to set a LayoutManager for your RecyclerView otherwise you will see an exception at Runtime:
所以我就把源代碼中的：
private final void setStatus(int resId)
private final void setStatus(CharSequence subTitle)
這兩個方法注釋掉，就可以正常運行了。