How is the internal dispatch mechanism implemented in the system?

In Android, the dispatcher mechanism is responsible for handling and distributing events, messages, and tasks between threads and application components.

The core internal dispatching mechanism in Android is implemented through the Looper class and its associated MessageQueue:

• Looper — is a message processing loop that continuously retrieves messages from the queue and passes them to the handler (Handler).
• MessageQueue — is the message queue where tasks and events are accumulated for processing.
• Handler — is an object that receives messages from the Looper and performs the corresponding actions.

Working principle:

1. In each thread that requires message processing, a Looper is created.
2. The Looper starts a loop that retrieves messages from the MessageQueue.
3. Each message is passed to the Handler associated with that Looper.
4. The Handler processes the message by invoking the necessary code.

This allows efficient management of asynchronous tasks and UI updates (which must be performed on the main thread).

Example:

Handler handler = new Handler(Looper.getMainLooper());
handler.post(() -> {
    // Code that runs on the main thread
});

Thus, the internal dispatching in Android is built on a message processing loop (Looper), a message queue, and handlers (Handler), which ensure sequential and thread-safe event processing.