前言

本文来自《Head Fist 设计模式》一书的实例，这里仅仅是个人笔记记录

需求

我需要一杯咖啡，但是需要加牛奶和白糖，请算出价格

我们可以拆解为咖啡，装饰着牛奶和白糖，例如像下面这样套着

/**     * 咖啡+牛奶+白糖     *      * 所谓装饰描述： 即原味咖啡的基础上，装饰： 牛奶 MilkCondiment，再装饰：白糖 SugarCondiment     */    private void updateUI() {        BaseBaverage mCoffee = new Coffee();        BaseBaverage mMilkCoffee = new MilkCondiment(mCoffee);        BaseBaverage mSugarMilkCoffee = new SugarCondiment(mMilkCoffee);        String result = mSugarMilkCoffee.getDiscribtion() + " cost = " + mSugarMilkCoffee.cost();        tv_info.setText(result);        Log.d(Contants.TAG, result);        //运行结果  Coffee + MilkCondiment + SugarCondiment cost = 22    }

上述不管是咖啡，还是配料牛奶、白糖都是继承同一个基类或超类，来着这样就可以上述进行相互组合了。

装饰者基类

package com.su.decoratormode.domain;public abstract class BaseBaverage {    // 便于知悉子类谁谁谁    public abstract String getDiscribtion();    // 价格咯    public abstract int cost();}

主料咖啡类

package com.su.decoratormode.domain;public class Coffee extends BaseBaverage {
       private static final int mCost = 15;    @Override    public String getDiscribtion() {        return Coffee.class.getSimpleName();    }    @Override    public int cost() {        return mCost;    }}

配料-牛奶

package com.su.decoratormode.domain;public class MilkCondiment extends BaseBaverage {
       private int mCost = 5;    private BaseBaverage mBaseBaverage;    public MilkCondiment(BaseBaverage mBaseBaverage) {        this.mBaseBaverage = mBaseBaverage;    }    @Override    public String getDiscribtion() {        return mBaseBaverage.getDiscribtion() + " + " + MilkCondiment.class.getSimpleName();    }    @Override    public int cost() {        return mCost + mBaseBaverage.cost();    }}

配料-白糖

package com.su.decoratormode.domain;public class SugarCondiment extends BaseBaverage {
       private int mCost = 2;    private BaseBaverage mBaseBaverage;    public SugarCondiment(BaseBaverage mBaseBaverage) {        this.mBaseBaverage = mBaseBaverage;    }    @Override    public String getDiscribtion() {        return mBaseBaverage.getDiscribtion() + " + " + SugarCondiment.class.getSimpleName();    }    @Override    public int cost() {        return mCost + mBaseBaverage.cost();    }}