android(4): 类库的学习

 android里面的类很多，都是有层次的。一般学习都是学一个忘一个，不成系统。很难有深刻的印象。

为此，在这里将学习过的类都记录下来。

1.android-widget

PopupWindow

简介：A popup window that can be used to display an arbitrary view. The popup window is a floating container that appears on top of the current activity.

2. android-app

AlertDialog

简介：A subclass of Dialog that can display one, two or three buttons. If you only want to display a String in this dialog box, use the setMessage() method. If you want to display a more complex view, look up the FrameLayout called "custom" and add your view to it: