关于 PopupWindow 响应 Back 按键收起

The reason the background cannot be null is because of what happens in

PopupWindow#preparePopup

. If it detects

background != null

it creates an instance of

PopupViewContainer

and calls

setBackgroundDrawable

on that and puts your content view in it.

PopupViewContainer

is basically a

FrameLayout

that listens for touch events and the

KeyEvent.KEYCODE_BACK

event to dismiss the window. If background == null, it doesn't do any of that and just uses your content view. You can, as an alternative to depending on

PopupWindow

to handle that, extend your root

ViewGroup

to behave the way you want.

PopupWindow

PopupViewContainer

PopupViewContainer

PopupWindow

ViewGroup 来处理监听。