Looper Handler Mssage

1. A handler has only one queue;
2. When invoking the Handler.post (Runnable Runnable) method, the Runnable is encapsulated as a message;
3. When the queue executes, it determines whether the current message encapsulates the runnable, and if it is closed, executes the runnable directly, and if not, passes the current message to Handlemessage (message msg) for processing;
4. Handler can be set at the time of instantiation a callback

Looper Handler Mssage