Choreographer is the one which acts like a interface between application view system and lower layer display system for rendering the views. ViewRootImpl is the ViewParent or root below which only Activity window DecorView will be attached. All the view layouts set by the activity through setContentView() will attached the DecorView whose parent is ViewRootImpl. Actually ViewRootImpl is not a View its just a ViewParent which handled and manages the View Hierarchies for displaying, handling input events etc.

In Android What is VSYNC and its usage? VSYNC is the event posted periodically by the kernal at fixed interval where the input handling, Animation and Window drawing happening synchroniiously at the same VSYNC interval. Below have given the detail explanation about the VSYNC event before VSYNC is introduced and after VSYNC is introduced. Before VSYNC is introduced: Before VSYNC is introduced then there was no synchronization happening for Input, animation and draw.

Aspect-oriented programming entails breaking down program logic into “concerns” (cohesive areas of functionality). This means, that with AOP, we can add executable blocks to some source code without explicitly changing it. This programming paradigm pretends that “cross-cutting concerns” (the logic needed at many places, without a single class where to implement them) should be implemented once and injected it many times into those places. Code injection becomes a very important part of AOP: it is useful for dealing with the mentioned “concerns” that cut across the whole application, such as logging or performance monitoring, and, using it in this way, should not be something used rarely as you might think, quite the contrary; every programmer will come into a situation where this ability of injecting code, could prevent a lot of pain and frustration.