父类:返回值是泛型；

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
public class Helper<T extends Helper> {
     protected T child;
     public Helper() {
            child = (T) this;
        }
     public T setText(@IdRes int viewId,String textStr) {
            ...
            checkChild();
            return child;
        }
     protected void checkChild() {
            if (child == null)
                throw new IllegalStateException("child must be set in child's Constructor!" +
                        "not method:initDefaultValueAnimator");
        }
}

子类:制定泛型 + 继承父类

  • 光继承，就已经包含扩展能力了。
  • warpper方法其实装饰器模式

    用到的地方:例如一个方法的参数是Helper类型，并且无法改变参数的类型。继而用装饰器扩展其功能

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
public class ExtraHelper<T extends ExtraHelper> extends Helper<T> {


    protected ExtraHelper(Helper helper) {
        super(helper.getContext(), helper.getHolder(), helper.getAdapter());
        child = (T) this;
    }

    public static ExtraHelper<ExtraHelper> wrapper(Helper helper) {
        return new ExtraHelper(helper);
    }

    public T heihei() {
        System.out.println("heihei!");
        checkChild();
        return child;
    }

    public T heihei2() {
        System.out.println("heihei2!");
        checkChild();
        return child;
    }
}

最后的使用

1
ExtraHelper.wrapper(helper).setText(R.id.tv, data).heihei().heihei2()

Demo
Demo2