我可以用构建器模式制作抽象片段 class 吗？

Question

我制作了一些片段扩展了topFragment class。但它有可变参数——自定义监听器、一些模型等。

public abstract class TopFragment extend Fragment {
    public interface OnCustomListener {
        void onCustomListener();
    }
    protected OnCustomListener onCustomListener;
    protected int importantValue;
    protected String importantString;

    protected abstract void doSomething();

    public static class Builder() {
        protected OnCustomListener onCustomListener;
        protected int importantValue;
        protected String importantString;

        public Builder(OnCustomListener onCustomListener) {
            this.onCustomListener = onCustomListener;
        }

        public Builder setValue(int value) {
            this.importantValue = value;
            return this;
        }

        public Builder setString(String value) {
            this.importantString = value;
            return this;
        }
    }
}

这是第二个片段class

public class SecondFragment extend TopFragment {
    @Override
    protected void doSomething() {
        // do something.
    }
}

public class ThirdFragment extend TopFragment {
    @Override
    protected void doSomething() {
        // do something.
    }
}

TopFragment fragment = new SecondFragment(); 有用。那么如何使用构建器创建继承片段 class 的实例？

Answer 1

class 的外部环境的实现绑定到 Builder，有一个私有的 Constructor，它接受一个 Builder 对象作为参数，例如

public class ThirdFragment extend TopFragment {
    @Override
    protected void doSomething() {
        // do something.
    }

   private ThirdFragment(Builder builder) {
      // use the members of builder to build your object
   } 
}

并且 Builder 本身有一个调用该构造函数的 build() 方法。例如

    public ThirdFragment build() {
        return new ThirdFragment(this);
    }

现在Fragment既不能有私有构造函数也不能有带参数的构造函数，所以你不能真正使用Builder模式。

我可以用构建器模式制作抽象片段 class 吗？

Can I make abstract fragment class with builder pattern?

android

builder-pattern

android-fragments