Loopers, MessageQueues, and Handlers provide one of the facilities for processes and threads to communicate with each other. They are also one of the basis to implement the Services of Android framework. The relationship between these classes and how they interact with each other are not so easy to be seen through at the first glance. And that's why there are so many articles talking about them. This post does not intend to show they are used, but focus on the relationship between them.
