PopupWindow的属性及用法

PopupWindow可实现弹窗效果，但是，Popupwidow没有默认布局，需要我们自己设置。
一.PopupWindow的API
构造方法摘要
PopupWindow() 
          Create a new empty, non focusable popup window of dimension (0,0).
 //创建一个空的、没有获取焦点的、长宽尺寸均为0的popup window
PopupWindow(Context context) 
          Create a new empty, non focusable popup window of dimension (0,0).
 //创建一个空的、没有获取焦点的、长宽尺寸均为0的popup window
PopupWindow(Context context, AttributeSet attrs) 
          Create a new empty, non focusable popup window of dimension (0,0).
 //创建一个空的、没有获取焦点的、长宽尺寸均为0的popup window
PopupWindow(Context context, AttributeSet attrs, int defStyle) 
          Create a new empty, non focusable popup window of dimension (0,0).
 //创建一个空的、没有获取焦点的、长宽尺寸均为0的popup window
PopupWindow(int width, int height) 
          Create a new empty, non focusable popup window.
 //创建一个没有获取焦点的、宽为width长为height的popup window
PopupWindow(View contentView) 
          Create a new non focusable popup window which can display the contentView.
 //创建一个没有获取焦点的、显示contentView的popup window
PopupWindow(View contentView, int width, int height) 
          Create a new non focusable popup window which can display the contentView.
 //创建一个没有获取焦点的、宽为width长为height显示contentView的popup window
PopupWindow(View contentView, int width, int height, boolean focusable) 
          Create a new popup window which can display the contentView.
 //创建一个根据focusable来判断是否获取焦点的、宽为width长为height显示contentView的popup window
方法摘要
 void dismiss() 
          Dispose of the popup window.
 //使popup window消失
 int getAnimationStyle() 
          Return the animation style to use the popup appears and disappears
 //返回该popup window出现或消失的动画类型，返回值为整型
 Drawable getBackground() 
          Return the drawable used as the popup window's background.
 //返回popup window的背景，返回值为Drawable类型
 View getContentView() 
          Return the view used as the content of the popup window.
 //返回popup window展示的内容,返回值为一个View
 int getHeight() 
          Return this popup's height MeasureSpec
 //返回该popup window的高度值，返回值为int型
 int getInputMethodMode() 
          Return the current value in setInputMethodMode(int).
 //返回当前popup window对输入法的设置模式
 int getMaxAvailableHeight(View anchor) 
          Returns the maximum height that is available for the popup to be completely shown.
 //返回能使当前popup window完整显示的最大高度
 int getMaxAvailableHeight(View anchor, int yOffset) 
          Returns the maximum height that is available for the popup to