设计模式学习之路-备忘录模式

备忘录模式，在不破坏封装性的前提下，捕获一个对象的内部状态，并在该对象之外保存这个状态。这样以后就可将该对象恢复到原先保存的状态。

这个模式也很简单，最主要是一种思想。逻辑缜密的人在设计框架时必然走到这里。我们看看UML类图。

 

基本逻辑代码：

class Originator{ private String state; public Memento createMemento(){  return (new Memento(state)); } public void setMemento(Memento m{   state = m.state;  }  public void show(){  //输出state }}

class Memento{ private String state; public Memento(String state){  this.state = state; } poublic String getState(){   return state; }}

class Caretaker{ private Memento m;  public void saveMemento(Memento m){  this.m = m;} public Memento getMemento(){  return m; }}

客户端调用

static void mian(String[] args){  Originator o = new Originator();  o.state = "on";  Caretaker c = new Caretaker();  c.setMemento(o.createMemento());  o.state = "off";  o.setMemento(c.getMemento()):}

代码一看都能明白，很简单。相信大家很多人小时候都玩过卡带游戏，带保存进度的那种游戏。每次在一个节点保存进度，在进入下一个节点，一旦失败了。可以恢复节点处的状态，这个就是典型的备忘录模式。这里就以游戏有例子。

备忘录类

package com.abings.mementomodel.MementoModel;/** * Created by HaomingXu on 2016/9/13. */public class Memento {    public String name;//姓名    public String sex;//性别    public String style;//职业    public String attckZB;//攻击装备    public String defineZB;//防御装备    public String lifeZB;//指环装备    public int attack;//攻击力    public int define;//防御值    public int life;//生命值    public int lan;//法力值    public Memento(String name, String sex, String style, String attckZB, String defineZB, String lifeZB, int attack, int define, int life, int lan) {        this.name = name;        this.sex = sex;        this.style = style;        this.attckZB = attckZB;        this.defineZB = defineZB;        this.lifeZB = lifeZB;        this.attack = attack;        this.define = define;        this.life = life;        this.lan = lan;    }    public Memento(){    }    public int getLan() {        return lan;    }    public void setLan(int lan) {        this.lan = lan;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getSex() {        return sex;    }    public void setSex(String sex) {        this.sex = sex;    }    public String getStyle() {        return style;    }    public void setStyle(String style) {        this.style = style;    }    public String getAttckZB() {        return attckZB;    }    public void setAttckZB(String attckZB) {        this.attckZB = attckZB;    }    public String getDefineZB() {        return defineZB;    }    public void setDefineZB(String defineZB) {        this.defineZB = defineZB;    }    public String getLifeZB() {        return lifeZB;    }    public void setLifeZB(String lifeZB) {        this.lifeZB = lifeZB;    }    public int getAttack() {        return attack;    }    public void setAttack(int attack) {        this.attack = attack;    }    public int getDefine() {        return define;    }    public void setDefine(int define) {        this.define = define;    }    public int getLife() {        return life;    }    public void setLife(int life) {        this.life = life;    }    @Override    public String toString() {        return "玩家{" +                "姓名：'" + name + '\'' +                "\n 性别：'" + sex + '\'' +                "\n 职业：'" + style + '\'' +                "\n 攻击装备：'" + attckZB + '\'' +                "\n 防御装备：'" + defineZB + '\'' +                "\n 指环：'" + lifeZB + '\'' +                "\n 攻击力：" + attack +                "\n 防御力：" + define +                "\n 生命值：" + life +                "\n 魔法值：" + lan +                '}';    }}

玩家类

package com.abings.mementomodel.Builder;import com.abings.mementomodel.MementoModel.Memento;/** * Created by HaomingXu on 2016/9/13. */public class Player extends Memento {    public Player(String name, String sex, String style, String attckZB, String defineZB, String lifeZB, int attack, int define, int life, int lan) {        super(name, sex, style, attckZB, defineZB, lifeZB, attack, define, life, lan);    }    public Player(){    }    //创建备忘录    public Memento createMemento(){        return (new Memento(name,sex,style,attckZB,defineZB,lifeZB,attack,define,life,lan));    }    //恢复状态    public void setMemento(Memento memento){        this.name = memento.getName();        this.sex = memento.getSex();        this.style = memento.getStyle();        this.attckZB = memento.getAttckZB();        this.defineZB = memento.getDefineZB();        this.lifeZB = memento.getLifeZB();        this.attack = memento.getAttack();        this.define = memento.getDefine();        this.life = memento.getLife();        this.lan = memento.getLan();    }    public void fightWithBoss(){        this.life = 0;        this.lan = 0;    }    @Override    public String toString() {        return super.toString();    }}

package com.abings.mementomodel.Builder;/** * Created by HaomingXu on 2016/9/13. */public abstract class Builder {    public abstract void setLan() ;    public abstract void setName() ;    public abstract void setSex() ;    public abstract void setStyle() ;    public abstract void setAttckZB() ;    public abstract void setDefineZB() ;    public abstract void setLifeZB() ;    public abstract void setAttack() ;    public abstract void setDefine() ;    public abstract void setLife() ;    public abstract Player getPlayer();}

建造者中指挥者

package com.abings.mementomodel.Builder;/** * Created by HaomingXu on 2016/9/13. */public class Director {    public static Player cratePlayer(Builder builder){        builder.setName();        builder.setSex();        builder.setAttack();        builder.setAttckZB();        builder.setDefine();        builder.setDefineZB();        builder.setLan();        builder.setLifeZB();        builder.setLife();        builder.setStyle();        return builder.getPlayer();    }}

package com.abings.mementomodel.MementoModel;/** * Created by HaomingXu on 2016/9/13. */public class Caretaker {    private Memento memento;    public Memento getMemento() {        return memento;    }    public void setMemento(Memento memento) {        this.memento = memento;    }}

客户端

package com.abings.mementomodel;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import com.abings.mementomodel.Builder.Director;import com.abings.mementomodel.Builder.Player;import com.abings.mementomodel.Builder.ZhanShiPlayer;import com.abings.mementomodel.MementoModel.Caretaker;public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        //创建角色，魔族战士        Player player = Director.cratePlayer(new ZhanShiPlayer());        //到了保存记录节点        Caretaker caretaker = new Caretaker();        //打boss之前保存状态        caretaker.setMemento(player.createMemento());        //打Boss之前的状态        Log.i("Tag", player.toString());        //单挑BOSS失败了        player.fightWithBoss();        //单挑之后的状态        Log.i("Tag", player.toString());        //读取记录，满血复活        player.setMemento(caretaker.getMemento());        //读取记录之后的状态        Log.i("Tag", player.toString());    }}

运行结果：

09-13 12:58:13.615 27181-27181/com.abings.mementomodel I/Tag: 玩家{姓名：'魔尊重楼'                                                               性别：'男'                                                               职业：'魔族战士'                                                               攻击装备：'魔族至尊饮血剑'                                                               防御装备：'魔族至尊反甲'                                                               指环：'魔族至尊狂澜铠甲'                                                               攻击力：3500                                                               防御力：3000                                                               生命值：6000                                                               魔法值：1500}09-13 12:58:13.615 27181-27181/com.abings.mementomodel I/Tag: 玩家{姓名：'魔尊重楼'                                                               性别：'男'                                                               职业：'魔族战士'                                                               攻击装备：'魔族至尊饮血剑'                                                               防御装备：'魔族至尊反甲'                                                               指环：'魔族至尊狂澜铠甲'                                                               攻击力：3500                                                               防御力：3000                                                               生命值：0                                                               魔法值：0}09-13 12:58:13.615 27181-27181/com.abings.mementomodel I/Tag: 玩家{姓名：'魔尊重楼'                                                               性别：'男'                                                               职业：'魔族战士'                                                               攻击装备：'魔族至尊饮血剑'                                                               防御装备：'魔族至尊反甲'                                                               指环：'魔族至尊狂澜铠甲'                                                               攻击力：3500                                                               防御力：3000                                                               生命值：6000                                                               魔法值：1500}

运用起来也很简单，客户端代码相当简洁。代码的扩展性，灵活性，维护性，可复用性都得到了一定的提升。只是这里面的逻辑有点绕。多学多用才是真理、git:

https://github.com/SingleShu/MementoModel