Listener and Adapter Listener&adapter

Why do I need adapter? Short answer: Simplifying

"Event Source" can register (addxxxlistener) Listener object and Send event object

WindowListener listener = ...; Frame.addwindowlistener (listener);

Specific event corresponding to a specific listener interface (Listener interface);

 Public Interface windowlistener{   void  windowopened (windowevent e);    void windowclosing (WindowEvent e);}

In order to handle a particular event, the listener implements the corresponding interface , which in Java means all methods (windowopened, windowclosing) that need to implement the interface . ）
But the listener may only be interested in one of these methods, and other methods don't need to do anything, so it can be tedious to implement:

class Implements windowlistener{    publicvoid  windowclosing (windowevent e) {        if  (user agrees)             System.exit (0);    }      Public void windowopened (WindowEvent e) {}    ...}

To simplify, each AWT listener interface with multiple methods has an adapter (Adapter) class that implements all the methods in the interface, but each method does nothing. Need to construct monitoring
Terminator_b, you only need to extend (extends) this adapter and overriding the function of interest. ：

In practice, when you create a listener class, we define the listener as an anonymous intrinsic to the event source, as follows:

Frame.addwindowlistener (new  windowadapter () {     publicvoid  Windowclosing (WindowEvent e) {          if(user agrees)              System.exit (0);     }});

Listener and Adapter Listener&adapter