装饰者模式

1.概述

所谓装饰，就是添加点特性或者说是行为，具体就是动态扩展对象功能，又称为包装模式。比如女生化妆。

2.UML结构图

image.png

3.代码实现：以化妆为例

Costmeic:共同接口

/**
 * Created by zhouwen on 2019/7/12 
 */
public abstract class Costmeic {

    public abstract void makeUp();
}

ConcreteCosmetic：被装饰者对象

/**
 * Created by zhouwen on 2019/7/12 
 */
public class ConcreteCosmetic extends Costmeic{
    @Override
    public void makeUp() {
        Logger.getLogger("ConcreteCosmetic").info("简单化妆");
    }
}

CosmeticDecorator：抽象装饰者，内部持有被装饰者的引用

/**
 * Created by zhouwen on 2019/7/12 
 */
public abstract class CosmeticDecorator extends Costmeic {

    private Costmeic mCostmeic;
    public CosmeticDecorator(Costmeic costmeic) {
        mCostmeic = costmeic;
    }

    @Override
    public void makeUp() {
        mCostmeic.makeUp();
    }
}

ConcreteCosmeticA：具体装饰者

/**
 * Created by zhouwen on 2019/7/12 
 */
public class ConcreteCosmeticA extends CosmeticDecorator {


    public ConcreteCosmeticA(Costmeic costmeic) {
        super(costmeic);
    }

    @Override
    public void makeUp() {
        super.makeUp();
        heavyMakeup();
        rouge();
    }

    private void rouge() {
        Logger.getLogger("ConcreteCosmeticA").info("涂深红口红");
    }

    private void heavyMakeup() {
        Logger.getLogger("ConcreteCosmeticA").info("加浓妆");
    }


}

ConcreteCosmeticB：具体装饰者

/**
 * Created by zhouwen on 2019/7/12 
 */
public class ConcreteCosmeticB extends CosmeticDecorator {

    public ConcreteCosmeticB(Costmeic costmeic) {
        super(costmeic);
    }

    @Override
    public void makeUp() {
        super.makeUp();
        heavyMakeup();
        rouge();
    }
    private void rouge() {
        Logger.getLogger("ConcreteCosmeticB").info("涂淡红口红");
    }

    private void heavyMakeup() {
        Logger.getLogger("ConcreteCosmeticB").info("淡妆");
    }

}

WrapperClient:场景类

/**
 * Created by zhouwen on 2019/7/12 
 */
public class WrapperClient {


    public void test(){

        Costmeic costmeic = new ConcreteCosmetic();

        ConcreteCosmeticA concreteCosmeticA = new ConcreteCosmeticA(costmeic);
        concreteCosmeticA.makeUp();

        ConcreteCosmeticB concreteCosmeticB = new ConcreteCosmeticB(costmeic);
        concreteCosmeticB.makeUp();

    }
}

4.与代理模式的区别

装饰模式是对对象的功能扩展，而代理模式是对对象进行控制，不做扩展。

5.android中Context的应用就是使用装饰者模式。