android 窗口焦点介绍

背景

我们经常会遇到一种Application does not hava focused window的ANR异常，这种异常一般是没有焦点窗口FocusedWindow导致,且这类异常只会发生在key事件的派发，因为key事件是需要找到一个焦点窗口然后再派发，而触摸事件只需要找到当前显示的窗口即可

关键日志

window

在dumpsys window中查看mCurrentFocus和mFocusedApp

  mCurrentFocus=Window{f96644 u0 NotificationShade}mFocusedApp=ActivityRecord{e9566ee u0 com.android.launcher3/.uioverrides.QuickstepLauncher} t12}

mCurrentFocus指的是当前的焦点窗口
mFocusedApp指的是当前的焦点Activity

查看有没有LAST ANR

WINDOW MANAGER LAST ANR (dumpsys window lastanr)<no ANR has occurred since boot>

这里没有LAST ANR，如果有，mCurrentFocus会显示null

input

在dumpsys input中查看FocusedApplications和FocusedWindows

  FocusedApplications:displayId=0, name='ActivityRecord{e9566ee u0 com.android.launcher3/.uioverrides.QuickstepLauncher} t12}', dispatchingTimeout=5000msFocusedWindows:displayId=0, name='f96644 NotificationShade'

如果发生ANR，焦点窗口以dumpsys input为主

event log

05-18 19:22:55.806   580   607 I input_focus: [Focus request f96644 NotificationShade,reason=UpdateInputWindows]
05-18 19:22:55.837   580   675 I input_focus: [Focus leaving e225d94 com.android.launcher3/com.android.launcher3.uioverrides.QuickstepLauncher (server),reason=Waiting for window because NO_WINDOW]
05-18 19:22:55.855   580   675 I input_focus: [Focus entering f96644 NotificationShade (server),reason=Window became focusable. Previous reason: NOT_VISIBLE]

request 和 entering正常情况下是一一对应，打印了entering则表示真正的焦点已经进入到对应的窗口
发生Application does not hava focused window时，一般request 有打印，我们可以通过是否有entering的打印来分析
1.entering部分有打印，代表焦点已经在input里面，但是仍然有ANR，就需要从input角度分析
2.entering部分未打印，代表input没有被触发焦点窗口设置到input，需排查SurfaceFlinger或WMS