两种类型：STARTING_WINDOW_TYPE_SNAPSHOT（任务快照-截屏-用于热起）、STARTING_WINDOW_TYPE_SPLASH_SCREEN（冷起）

启动一个activty

frameworks\base\core\java\android\app\Instrumentation.java#execStartActivity

frameworks\base\services\core\java\com\android\server\wm\ActivityTaskManagerService.java#startActivity

初始化 ActivityStarter ，并且执行启动

frameworks\base\services\core\java\com\android\server\wm\ActivityStarter.java#execute

frameworks\base\services\core\java\com\android\server\wm\ActivityStarter.java#executeRequest

frameworks\base\services\core\java\com\android\server\wm\ActivityStarter.java#startActivityUnchecked

frameworks\base\services\core\java\com\android\server\wm\ActivityStarter.java#startActivityInner

frameworks\base\services\core\java\com\android\server\wm\Task.java#resumeTopActivityInnerLocked

显示StartingWindow

frameworks\base\services\core\java\com\android\server\wm\ActivityRecord.java#showStartingWindow

frameworks\base\services\core\java\com\android\server\wm\ActivityRecord.java#addStartingWindow

frameworks\base\services\core\java\com\android\server\wm\ActivityRecord.java#scheduleAddStartingWindow

frameworks\base\services\core\java\com\android\server\wm\StartingSurfaceController.java#createSplashScreenStartingSurface

frameworks\base\services\core\java\com\android\server\wm\StartingSurfaceController.java#createTaskSnapshotSurface

frameworks\base\services\core\java\com\android\server\wm\TaskOrganizerController.java#addStartingWindow

在WMShell中添加StartingWindow

frameworks\base\libs\WindowManager\Shell\src\com\android\wm\shell\ShellTaskOrganizer.java#addStartingWindow

根据不同的type添加对应的StartingWindow，如果是Snapshot类型的StartingWindow会在主动调用WMS的addwindow和relayout方法，而SplashScreen类型的会走ViewRootImpl的流程

frameworks\base\libs\WindowManager\Shell\src\com\android\wm\shell\startingsurface\StartingWindowController.java#addStartingWindow

frameworks\base\libs\WindowManager\Shell\src\com\android\wm\shell\startingsurface\StartingSurfaceDrawer.java#addSplashScreenStartingWindow

Window第一帧绘制完毕

frameworks\base\services\core\java\com\android\server\wm\WindowManagerService.java#finishDrawingWindow

更新 mDrawState改成COMMIT_DRAW_PENDING

frameworks\base\services\core\java\com\android\server\wm\WindowStateAnimator.java#finishDrawingLocked

遍历Window

frameworks\base\services\core\java\com\android\server\wm\DisplayContent.java#mApplySurfaceChangesTransaction

更新mDrawState状态为READY_TO_SHOW

frameworks\base\services\core\java\com\android\server\wm\WindowStateAnimator.java#commitFinishDrawingLocked

针对于不同类型的window处理的方式不一样。如果是StartingWindow就会显示StartingWindow

frameworks\base\services\core\java\com\android\server\wm\WindowState.java#performShowLocked

        if (mAttrs.type != TYPE_APPLICATION_STARTING) {
            mActivityRecord.onFirstWindowDrawn(this, mWinAnimator);
        } else {
            mActivityRecord.onStartingWindowDrawn();
        }

当是App第一帧绘制完毕时，会移除StartingWindow

frameworks\base\services\core\java\com\android\server\wm\ActivityRecord.java#onFirstWindowDrawn

frameworks\base\services\core\java\com\android\server\wm\ActivityRecord.java#removeStartingWindow

frameworks\base\services\core\java\com\android\server\wm\StartingSurfaceController$ShellStartingSurface.java#remove

frameworks\base\services\core\java\com\android\server\wm\TaskOrganizerController.java#removeStartingWindow

frameworks\base\services\core\java\com\android\server\wm\TaskOrganizerController$TaskOrganizerCallbacks.java#removeStartingWindow

调用WMShell来移除Window

frameworks\base\libs\WindowManager\Shell\src\com\android\wm\shell\ShellTaskOrganizer.java#removeStartingWindow

frameworks\base\libs\WindowManager\Shell\src\com\android\wm\shell\startingsurface\StartingSurfaceDrawer.java#removeStartingWindow

frameworks\base\libs\WindowManager\Shell\src\com\android\wm\shell\startingsurface\StartingSurfaceDrawer.java#removeWindowInner

frameworks\base\services\core\java\com\android\server\wm\WindowManagerService.java#removeWindow