Android常用设计模式

记一下Android常用的设计模式：

1.单例模式：

/** 单例模式* */public class Singleton {    private static volatile Singleton singleton = null;    private Singleton() {    }    public static Singleton getInstance() {        if (singleton == null) {            synchronized (Singleton.class) {                if (singleton == null) {                    singleton = new Singleton();                }            }        }        return singleton;    }}

2.建造者模式：

/** * 建造者模式 */public class Person {    private String name;    private String age;    private double height;    private double weight;    public Person(Builder builder) {        this.name = name;        this.age = age;        this.height = height;        this.weight = weight;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getAge() {        return age;    }    public void setAge(String age) {        this.age = age;    }    public double getHeight() {        return height;    }    public void setHeight(double height) {        this.height = height;    }    public double getWeight() {        return weight;    }    public void setWeight(double weight) {        this.weight = weight;    }    static class Builder {        private String name;        private int age;        private double height;        private double weight;        public Builder name(String name) {            this.name = name;            return this;        }        public Builder age(int age) {            this.age = age;            return this;        }        public Builder height(double height) {            this.height = height;            return this;        }        public Builder weight(double weight) {            this.weight = weight;            return this;        }        public Person build() {            return new Person(this);        }    }}

使用：

Person.Builder builder=new Person.Builder();builder.age(12).name("测试").height(12).weight(12).build();

3.观察者模式：

先定义一个接口：

public interface Observer {    void onUpdate(Observable observable,T data);}

//观察者public class Observable {    List> mObservers = new ArrayList>();    public void register(Observer observer) {        if (observer == null) {            throw new NullPointerException("observer == null");        }        synchronized (this) {            if (!mObservers.contains(observer))                mObservers.add(observer);        }    }    public synchronized void unregister(Observer observer) {        mObservers.remove(observer);    }    public void notifyObservers(T data) {        for (Observer observer : mObservers) {            observer.onUpdate(this, data);        }    }}

//实体类public class Weather {    private String description;    public Weather(String description) {        this.description = description;    }    public String getDescription() {        return description;    }    public void setDescription(String description) {        this.description = description;    }    @Override    public String toString() {        return "Weather{" +                "description='" + description + '\'' +                '}';    }}使用:

Observableobservable=new Observable<>();Observerobserver=new Observer() {    @Override    public void onUpdate(Observable observable, Weather data) {    }};Observerobserver2=new Observer() {    @Override    public void onUpdate(Observable observable, Weather data) {    }};observable.register(observer);observable.register(observer2);Weather weather=new Weather("好天气");observable.notifyObservers(weather);

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