41 Observer pattern

Observer:

defines a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.

Principles:

Strive for loosely coupled designs between objects that interact. (Observer pattern)

Class diagram:

Java's built-in Observer Pattern

abstract class:

java.util.observerable

(1)must be extended

(2)must call setChaged() before notifyObservers()

interface:

java.util.observer

=============================================================

class:

 android.database.Observable<T>    ↳android.database.ContentObservableabstract class:

android.database.ContentObserver

=============================================================

abstract class:

android.content.ContentProvider

android.content.ContentResolver

android.database.ContentObserver

ContentProvider-->ContentResolver-->ContentObserver

Context.getContentResolver();