设计模式之命令模式

命令模式

命令模式UML.png

class GameBoy{
    public void toLeft(){
        //左移
    }
    public void toRight(){
        //右移
    }
    public void toTop(){
        //上移
    }
    public void toBottom(){
        //下移
    }
    public void toA(){
        //A键出拳
    }
    public void toB(){
        //B键踢腿
    }
}

GameBoy,游戏机类

interface Command{
    void execute();
}

按钮接口

class LeftCommand implements Command{
    private GameBoy gameBoy;
    public LeftCommand(GameBoy gameBoy){
        this.gameBoy = gameBoy;
    }
    public void execute(){
        gameBoy.toLeft();
    }
}

class RightCommand implements Command{
    private GameBoy gameBoy;
    public RightCommand(GameBoy gameBoy){
        this.gameBoy = gameBoy;
    }
    public void execute(){
        gameBoy.toRight();
    }
}   

class TopCommand implements Command{
    private GameBoy gameBoy;
    public TopCommand(GameBoy gameBoy){
        this.gameBoy = gameBoy;
    }
    public void execute(){
        gameBoy.toTop();
    }
}   

class BottomCommand implements Command{
    private GameBoy gameBoy;
    public BottomCommand(GameBoy gameBoy){
        this.gameBoy = gameBoy;
    }
    public void execute(){
        gameBoy.toBottom();
    }
}   

class ACommand implements Command{
    private GameBoy gameBoy;
    public ACommand(GameBoy gameBoy){
        this.gameBoy = gameBoy;
    }
    public void execute(){
        gameBoy.toA();
    }
}   


class BCommand implements Command{
    private GameBoy gameBoy;
    public BCommand(GameBoy gameBoy){
        this.gameBoy = gameBoy;
    }
    public void execute(){
        gameBoy.toB();
    }
}   

上述六个类是具体的按键 上下左右AB键

class Buttons{
    private Command leftCommand,rightCommand,topCommand,bottomCommand,aCommand,bCommand;
    public Buttons(Command leftCommand, Command rightCommand, Command topCommand, Command bottomCommand, Command aCommand, Command bCommand){
        this.leftCommand = leftCommand;
        this.rightCommand = rightCommand;
        this.topCommand = topCommand;
        this.bottomCommand = bottomCommand;
        this.aCommand = aCommand;
        this.bCommand = bCommand;
    }
    public void toLeft(){
        leftCommand.execute();
        //左移
    }
    public void toRight(){
        rightCommand.execute();
        //右移
    }
    public void toTop(){
        topCommand.execute();
        //上移
    }
    public void toBottom(){
        bottomCommand.execute();
        //下移
    }
    public void toA(){
        ACommand.execute();
        //A键出拳
    }
    public void toB(){
        BCommand.execute();
        //B键踢腿
    }
    
}

键盘按钮类，开关类

public class Client{
    public static void main(String[] args){
        GameBoy gameBoy = new GameBoy();//游戏机先创建出来
        // 上下左右AB命令
        Command leftCommand,rightCommand,topCommand,bottomCommand,aCommand,bCommand;
        leftCommand = new LeftCommand(gameBoy);
        rightCommand = new RightCommand(gameBoy);
        topCommand = new TopCommand(gameBoy);
        bottomCommand = new BottomCommand(gameBoy);
        aCommand = new ACommand(gameBoy);
        bCommand = new BCommand(gameBoy);
        
        // 具体操作的按键
        Buttons buttons = new Buttons(leftCommand,rightCommand,topCommand,bottomCommand,aCommand,bCommand);
        //按键按下执行操作
        buttons.toLeft();
        buttons.toRight();
        buttons.toTop();
        buttons.toBottom();
        buttons.toA();
        buttons.toB();
    }       
}

个人总结

上述用例讲的是一个小游戏机运用了命令模式，将按钮这个动作请求和具体实现功能解耦。功能上的解耦伴随的代价是类的数量的增多，在实际开发中根据场景来考量是否采用。