设计模式（四）装饰器模式

装饰器模式

1、意图

动态增加功能，相比于继承更加灵活

2、类图

Component(VisualComponent)：定义一个对象接口，可以给这些对象动态地添加职责。ConcreteComponent(TextView)：定义一个对象，可以给这个对象添加一些职责。

Decorator：维持一个指向Component对象的指针，并定义一个与Component接口一致的接口。ConcreteDecorator(BorderDecorator、ScrollDecorator)：向组件添加职责。

3、实现

public interface Component {
    void draw();
}

public class ConcreteComponent implements Component{

    @Override
    public void draw() {
        System.out.println("展示一个窗口");
    }
}

 抽象类实现接口

public abstract class Decorator implements Component{
    public Component component;

    Decorator(Component component){
        this.component=component;
    }

    @Override
    public void draw() {
        component.draw();
    }
}

public class ConcreteDecorator1 extends Decorator{
    ConcreteDecorator1(Component component) {
        super(component);
    }

    @Override
    public void draw() {
        System.out.println("给窗口加边框");
        super.draw();
    }
}

public class ConcreteDecorator2 extends Decorator{
    ConcreteDecorator2(Component component) {
        super(component);
    }

    @Override
    public void draw() {
        System.out.println("给窗口加滚动条");
        super.draw();
    }
}

public class test {
    public static void main(String[] args) {
        Component concreteComponent=new ConcreteComponent();
        Decorator decorator1=new ConcreteDecorator1(concreteComponent);
        decorator1.draw();
        System.out.println("------------------------------");
        Decorator decorator2=new ConcreteDecorator2(concreteComponent);
        decorator2.draw();
    }
}

4、效果