android設計模式二十三式（三）——建造者模式（Builder）

Build模式/建造者模式

Build模式，在開發中非常常見，也很實用，最常見的，就是創建Dialog的時候，用起來，有點像鏈式調用，看一下我用build模式寫的一個Data對象的調用方法。

創建一個Data對象

 Data data = new Data.Builder()
                .category(getCategory())
                .owner(getOwner())
                .content(getContent())
                .keys(getKeys())
                .uuid(uuid)
                .build();

這樣就可以了，省去了繁瑣的set方法，也不用在Data對象中寫入繁瑣的不同的有參構造函數來創建對象，有了build類，我們可以隨意傳入參數個數，調用build方法建造出一個對象。

靜態內部類的Build對象，避免了內部類對外部類引用從而導致內存泄漏，靜態內部類的生命週期，和普通類一樣，new出來創建，系統回收，注意處理好靜態內部類的靜態成員變量引用，建議靜態內部類中不要寫靜態的成員變量。

public class Data {
    private String uuid,owner,category,content;
    private Keys keys;

    public Data() {

    }

    private Data(Builder builder) {
        this.uuid = builder.uuid;
        this.owner = builder.owner;
        this.category = builder.category;
        this.content = builder.content;
        this.keys = builder.keys;
    }

    public String getUuid() {
        return uuid;
    }

    public void setUuid(String uuid) {
        this.uuid = uuid;
    }

    public String getOwner() {
        return owner;
    }

    public void setOwner(String owner) {
        this.owner = owner;
    }

    public String getCategory() {
        return category;
    }

    public void setCategory(String category) {
        this.category = category;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public Keys getKeys() {
        return keys;
    }

    public void setKeys(Keys keys) {
        this.keys = keys;
    }

    public static class Builder {
        private String uuid,owner,category,content;
        private Keys keys;

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

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

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

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

        public Builder keys(Keys keys){
            this.keys = keys;
            return this;
        }

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