W/ViewRootImpl:由于没有窗口焦点而取消事件:MotionEvent？

Question

每次从儿童活动回到父活动时,我都会收到此错误消息？

 W/ViewRootImpl: Cancelling event due to no window focus: MotionEvent { action=ACTION_CANCEL, actionButton=0, id[0]=0, x[0]=440.365, y[0]=825.35156, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=1186212, downTime=1185113, deviceId=0, source=0x1002 } 

有人遇到过这样的错误吗？