Android in-depth design mode (a) delegate mode

(a) Introduction to the model of entrustment

The delegate mode is one of the basic design patterns. delegate, which is to let another object help you do things.

Many other patterns, such as state mode, policy mode, and visitor pattern, are essentially delegate patterns in more special situations.

The delegate pattern allows us to use aggregations instead of inheritance, java-combinations better than inheritance.

The simplest Java delegate mode

Class Realprinter {    void print () {        System.out.println ("Real Printer");}    } Class Printer {     realprinter realprinter = new Realprinter ();     public void print () {        realprinter.print ();     }}

/** * Simple Delegate mode *  * @author Peter_wang * @create-time 2014-5-19 pm 5:39:42 */public class Delegationdemo {    /**     * @param args */public    static void Main (string[] args) {        Printer Printer = new Printer ();        Printer.print ();    }}

(ii) The delegation mode in Android

The Listerner event in Android is a delegate mode, such as a button click event. Let's simulate how the entire click event is using the delegate model.

/** * Analog Basic View *  * @author Peter_wang * @create-time 2014-5-19 pm 5:03:55 */public Class View {    private onclicklist Ener Monclicklistener;    /**     * Analog Click event */public    void Clickevent () {        if (monclicklistener! = null) {            Monclicklistener.onclick (this);        }    }    public void Setonclicklistener (Onclicklistener onclicklistener) {        this.monclicklistener = Onclicklistener;    }    /**     * Click event interface     *      * @author peter_wang     * @create-time 2014-5-19 pm 5:05:45    */Public Interface Onclicklistener {public        void OnClick (View v);    }}

/** * Analog button *  * @author Peter_wang * @create-time 2014-5-19 pm 5:17:57 */public class Button    extends View {}

/** * Simulated basic Activity class *  * @author Peter_wang * @create-time 2014-5-19 pm 5:20:38 */public class Activity {public    STA tic void Main (string[] args) {        activity activity = new activity ();        Activity.oncreate ();    }    /**     * Analog OnCreate method     *    /protected void OnCreate () {    }}

/** * Commissioned Simulation page *  * @author Peter_wang * @create-time 2014-5-19 pm 5:19:22 */public class delegationactivity    extends A Ctivity    implements Onclicklistener {    private Button Mbutton;    @Override    protected void OnCreate () {        super.oncreate ();        Mbutton = new Button ();        Mbutton.setonclicklistener (this);        Analog Click event        mbutton.clickevent ();    }    @Override public    void OnClick (View v) {        if (v = = Mbutton) {            System.out.println ("OnClick () is callback!");        }    }}