Android message mechanism (2)

1. The message queue of Android is like a tunnel. The message is like a vehicle. It is first-in-first-out.

2. The message sending thread does not block the thread, while the message receiving thread blocks the thread. This is the handler mechanism of Android. After handler finishes processing a message object, it will continue to fetch the next message for processing.

3. There is no global messagequeue in Android. Different APK files cannot be communicated through messagequeue.

4. android UI cannot be updated directly by using the Java thread, because Android view is not completely designed by the thread. However, Android provides several methods for developers to update the UI in the thread, as follows:

Activity. runonuithread (runnable)
View. Post (runnable)
View. postdelayed (runnable, long)
Hanlder