定義:將一個(gè)復(fù)雜對(duì)象的構(gòu)建與它的表示分離,使得同樣地構(gòu)建過(guò)程可以創(chuàng)建不同的表示

使用場(chǎng)景示例
我們有一個(gè)產(chǎn)品,它包含了很多屬性

    public class Product{
        private String name;
        private String num;
        private String price;
        private String weight;
    }

在構(gòu)造的時(shí)候通常我們使用構(gòu)造函數(shù)進(jìn)行初始化,但是面對(duì)許多需要初始化的屬性并且有時(shí)并不需要初始化所有的屬性.?構(gòu)造函數(shù)就要重載,并且?guī)еL(zhǎng)長(zhǎng)的參數(shù),而建造模式就是把構(gòu)建分離出來(lái)
下面是代碼

public class Product {
    private String name;
    private String num;
    private String price;
    private String weight;

    public Product(Builder builder) {
        this.name = builder.name;
        this.num = builder.num;
        this.price = builder.price;
        this.weight = builder.weight;
    }

    public static class Builder {
        private String name;
        private String num;
        private String price;
        private String weight;

        public Builder setName(String name) {
            this.name = name;
            return this;
        }

        public Builder setNum(String num) {
            this.num = num;
            return this;
        }

        public Builder setPrice(String price) {
            this.price = price;
            return this;
        }

        public Builder setWeight(String weight) {
            this.weight = weight;
            return this;
        }

        public Product create() {
            return new Product(this);
        }

    }

}

Product.Builder builder = new Product.Builder();
Product product = builder.setName("macbook").setNum("10").create();

這種模式隨處可見(jiàn),典型的AlertDialog

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());

        LayoutInflater inflater = getActivity().getLayoutInflater();
        View view = inflater.inflate(R.xxx, null);
        builder.setView(view).setNegativeButton(DISMISS, null);
        return builder.create();
    }

還有URI

Uri uri = new Uri.Builder()
    .scheme("xxx")
    .path(String.valueOf(R.drawable.xxx))
    .build();