GestureBinding
AddCallback
PointerEvent
entry.target.handleEvent
hover/add
down
add(this)
HitTest->add子View循环向下查找
RendererBinding.hitTest
dispatchEvent
PointerRouter.route
_RouteEntry.route
RendererBinding
hitTest
RenderObject.hitTest
HitTestTarget
handleEvent
_hitTests
add(renderView)
RenderObject
remove
up
_handlePointerEvent
调用Callback
PointerRouter
_RouteEntry
pointerRouter.route
PointerRouter.addRoute
