在安卓4.4.2的关于蓝牙开发的一个sample BluetoothChat中，调试时，老是出错：Attempt to invoke virtual method 'void android.app.ActionBar.setTitle
上网查了一下，是这么说的：
（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:
所以我就把源代码中的：
private final void setStatus(int resId)
private final void setStatus(CharSequence subTitle)
这两个方法注释掉，就可以正常运行了。