Line by Line Walkthrough
In arrowpad.h we define the ArrowPad subclass which is a subclass of QWidget. In the screenshot above, the central widget with the four buttons is an ArrowPad.
 class ArrowPad : public QWidget
 {
     Q_OBJECT
When lupdate is run it not only extracts the source texts but it also groups them into contexts. A context is the name of the class in which the source text appears. Thus, in this example, "ArrowPad" is a context: it is the context of the texts in the ArrowPad class. The Q_OBJECT macro defines tr(x) in ArrowPad like this:
 qApp->translate("ArrowPad", x)
Knowing which class each source text appears in enables Qt Linguist to group texts that are logically related together, e.g. all the text in a dialog will have the context of the dialog's class name and will be shown together. This provides useful information for the translator since the context in which text appears may influence how it should be translated. For some translations keyboard accelerators may need to be changed and having all the source texts in a particular context (class) grouped together makes it easier for the translator to perform any accelerator changes without introducing conflicts.
In arrowpad.cpp we implement the ArrowPad class.
武汉部分大学生依赖手机 起床刷微博睡前聊微信
 　　“起床刷微博，睡前聊微信，上课看‘人人’，路上淘商城。”这句话在武汉不少校园网上甚为流传，也是许多大学生的真实生活写照。为了了解手机对大学生日常生活带来的影响，华中师范大学教育部人文社会科学研究项目课题组在武汉部分高校进行了一次调查。

　　据介绍，该课题组在武汉大学、华中师范大学、中国地质大学（武汉）、湖北大学、华中师大武汉传媒学院等7所高校共发放问卷1400份，回收有效问卷1256份。结果显示，80.8%的学生使用的都是方便上网的智能手机，其中57.3%的学生坦言自己是手机网民，对各种上网软件十分熟悉；47%的大学生表示手机时刻不能离身，14%的大学生称若离开移动的手机网络世界会很痛苦。

　　在问到“过度依赖手机对生活有何影响”时，35%的学生称会耗费学习时间，22.6%的学生认为会影响人际关系。一名参与调查的大学生表示，许多同学都有边走边玩手机的习惯，就连聊天都心不在焉。同时，也有57%的学生认为手机能帮助他们走在资讯前沿，缓解各种压力。

　　对此调查结果，该课题组负责人周挥辉建议，高校应多开展富有特点的校园文化活动，并通过课程、讲座引导大学生形成科学的网络文化价值观。同时，大学生也应学会自制、自律，理性上网。