android os 记事本功能的练习例子，包括UI,SQlite的操作，分三个阶段完成功能，文件名结尾为_Solution的文件是解决方案，可以对应该文件练习，代码有注释-android os Notepad function of exercise examples, including the UI, SQlite operation, completion in three phases, the file name ends with _Solution file is the sol