分屏流程

WindowSurfacePlacer$Traverser -->performSurfacePlacement -->WindowAnimator --> animate

Task --> dispatchTaskInfoChangedIfNeeded

ActivityTaskManagerService -- >WindowOrganizerController --> TaskOrganizerController

-->dispatchPendingEvents --> onTaskInfoChanged

TaskOrganizer --> onTaskInfoChanged

ShellTaskOrganizer -->onTaskInfoChanged

LegacySplitScreenTaskListener --> onTaskInfoChanged -->handleTaskInfoChanged

LegacySplitScreenController ->startEnterSplit --> update -- > addDivider

DividerView