定义

将一个复杂对象的构建与它的表示分离,使得同样的构建过程可以创建不同的表示

你看懂了吗? 反正我是一脸懵逼

UML类图

解读:

  • Product产品类: 产品抽象类
  • Builder: 抽象Builder类,规划产品组建,一般是由子类实现具体的组建过程
  • ConcreteBuilder: 具体的Builder类
  • Director: 统一组建过程

好吧, 还是说的有点虚呀, 来一个简单例子

简单实现

Computer抽象类类：Product角色，即产品抽象类

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/**
 * Created by allever on 17-5-18.
 * 计算机抽象类: Product角色*/
public abstract class Computer {
    private String strBoard;
    private String strDisplay;
    private String strOS;
    protected Computer(){}
    /**CPU核心数*/
    public void setBoard(String board){
        this.strBoard = board;
    }
    public void setDisplay(String display){
        this.strDisplay = display;
    }
    public void setStrOS(String os){
        this.strOS = os;
    }
    @Override
    public String toString() {
        String result = "Computer:\nboard=" + strBoard + "\ndisplay = " + strDisplay + "\nOS = " + strOS;
        return result;
    }
}

MacBook类，具体Computer类

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/**
 * Created by allever on 17-5-18.
 */
public class MacBook extends Computer {
    protected MacBook(){}
}

##Builder抽象类
负责规范产品组建，一般是由子类实现具体的组建过程

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/**
 * Created by allever on 17-5-18.
 * 抽象Builder类*/
public abstract class Builder {
    public abstract void buildBoard(String board);
    public abstract void buildDisplay(String display);
    public abstract void buildOS(String os);
    public abstract Computer build();
}

MacBookBuilder：具体Builder类，ConcreteBuilder角色

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/**
 * Created by allever on 17-5-18.
 * Builder实现类*/
public class MacBookBuilder extends Builder {
    private Computer computerMacBook = new MacBook();
    @Override
    public void buildBoard(String board) {
        computerMacBook.setBoard(board);
    }
    @Override
    public void buildDisplay(String display) {
        computerMacBook.setDisplay(display);
    }
    @Override
    public void buildOS(String os) {
        computerMacBook.setStrOS(os);
    }
    @Override
    public Computer build() {
        return computerMacBook;
    }
}

Director类：同一组装过程

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/**
 * Created by allever on 17-5-18.
 * Director类： 负责构建Computer*/
public class Director {
    private Builder builder = null;
    public Director(Builder builder){
        this.builder = builder;
    }
    //构建对象
    public void construct(String board, String display, String os){
        builder.buildBoard(board);
        builder.buildDisplay(display);
        builder.buildOS(os);
    }
}

客户端调用

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Builder builder = new MacBookBuilder();
Director director = new Director(builder);
director.construct("英特尔酷睿i7","15.6寸","Ubuntu 16.04");
Log.d(TAG, builder.build().toString());
Toast.makeText(BuildPatternsActivity.this,builder.build().toString(),Toast.LENGTH_LONG).show();

小提示

通常,Director角色会被省略,直接使用Builder构建对象,这个Builder通常为链式调用,即buildXXX()方法返回自身,return this;

修改后的Builder类

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/**
 * Created by allever on 17-5-18.
 * 抽象Builder类*/
public abstract class Builder {
    public abstract Builder buildBoard(String board);
    public abstract Builder buildDisplay(String display);
    public abstract Builder buildOS(String os);
    public abstract Computer build();
}

MacBookBuilder:

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/**
 * Created by allever on 17-5-18.
 * Builder实现类*/
public class MacBookBuilder extends Builder {
    private Computer computerMacBook = new MacBook();
    @Override
    public MacBookBuilder buildBoard(String board) {
        computerMacBook.setBoard(board);
        return this;
    }
    @Override
    public MacBookBuilder buildDisplay(String display) {
        computerMacBook.setDisplay(display);
        return this;
    }
    @Override
    public MacBookBuilder buildOS(String os) {
        computerMacBook.setStrOS(os);
        return this;
    }
    @Override
    public Computer build() {
        return computerMacBook;
    }
}

在客户端中的调用

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Builder builder = new MacBookBuilder();
//Director director = new Director(builder);
//director.construct("英特尔酷睿i7","15.6寸","Ubuntu 16.04");
Log.d(TAG, builder.buildBoard("英特尔酷睿i7")
                    .buildDisplay("15.6寸")
                    .buildOS("Max OS")
                    build().toString());

现在你是不是感觉到很熟悉的呢? 就像Android中构建一个Notification对象

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Notification notification = new NotificationCompat.Builder(this)
        .setContentTitle("This is content title")
        .setContentText("This is content text")
        .setSmallIcon(R.mipmap.ic_launcher)
        .setLargeIcon(BitmapFactory.decodeResource(getResources(),R.mipmap.ic_launcher))
        .setWhen(System.currentTimeMillis())
        //设置点击行为
        .setContentIntent(pendingIntent)
        //点击后消失
        .setAutoCancel(true)
        //设置声音
        .setSound(Uri.fromFile(new File("/system/media/audio/ringtones/Luna.ogg")))
        //设置震动 震动1s 静止1s 震动1s 要申明权限
        .setVibrate(new long[]{0, 1000,1000,1000})
        //设置呼吸灯闪烁
        .setLights(Color.GREEN, 1000, 1000)
        //设置默认
        .setDefaults(NotificationCompat.DEFAULT_ALL)
        //设置长文本
        .setStyle(new NotificationCompat.BigTextStyle().bigText("An Activity is an application component that provides a screen with which users can interact in order to do something, such as dial the phone, take a photo, send an email, or view a map."))
        //设置展开大图,,设置了长文本会看不到
        .setStyle(new NotificationCompat.BigPictureStyle().bigPicture(BitmapFactory.decodeResource(getResources(),R.mipmap.expensive)))
        //设置通知重要程度
        .setPriority(NotificationCompat.PRIORITY_MAX)
        .build();