【EventBus】事件通信框架 ( 实现几个关键的封装类 | 消息中心 | 订阅注解 | 订阅方法封装 | 订阅对象-方法封装 | 线程模式 )

package com.eventbus_demo.myeventbus;
public class MyEventBus {
    /**
     * 全局单例
     */
    private static MyEventBus instance;
    private MyEventBus() {
    }
    public static MyEventBus getInstance() {
        if (instance == null) {
            instance = new MyEventBus();
        }
        return instance;
    }
}

package com.eventbus_demo.myeventbus;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Retention(RetentionPolicy.RUNTIME)     // 该注解保留到运行时
@Target(ElementType.METHOD)             // 该注解作用于方法
public @interface MySubscribe {
    /**
     * 注解属性, 设置线程模式, 默认是 POSTING,
     *      即在发布线程调用订阅方法
     * @return
     */
    MyThreadMode threadMode() default MyThreadMode.POSTING;
}

package com.eventbus_demo.myeventbus;
import java.lang.reflect.Method;
/**
 * 该类中用于保存订阅方法相关信息
 */
public class MySubscriberMethod {
    /**
     * 订阅方法
     */
    private final Method method;
    /**
     * 订阅方法的线程模式
     */
    private final MyThreadMode threadMode;
    /**
     * 订阅方法接收的事件类型
     */
    private final Class<?> eventType;
    public MySubscriberMethod(Method method, MyThreadMode threadMode, Class<?> eventType) {
        this.method = method;
        this.threadMode = threadMode;
        this.eventType = eventType;
    }
    public Method getMethod() {
        return method;
    }
    public MyThreadMode getThreadMode() {
        return threadMode;
    }
    public Class<?> getEventType() {
        return eventType;
    }
}

package com.eventbus_demo.myeventbus;
/**
 * 封装 订阅者对象 与 订阅方法
 */
public class MySubscription {
    /**
     * 订阅者对象
     */
    private final Object subscriber;
    /**
     * 订阅方法
     */
    private final MySubscriberMethod subscriberMethod;
    public MySubscription(Object subscriber, MySubscriberMethod subscriberMethod) {
        this.subscriber = subscriber;
        this.subscriberMethod = subscriberMethod;
    }
    public Object getSubscriber() {
        return subscriber;
    }
    public MySubscriberMethod getSubscriberMethod() {
        return subscriberMethod;
    }
}

package com.eventbus_demo.myeventbus;
/**
 * 直接使用 EventBus 中的现成模式
 */
public enum MyThreadMode {
    POSTING,
    MAIN,
    MAIN_ORDERED,
    BACKGROUND,
    ASYNC
}