前言

Android EventBus这个知识点呢，我已经写了两篇文章，一篇是Android EventBus3.0使用详情，一篇是Android 浅谈EventBus源码，这两个篇文章讲了它的一个使用，还有源码解析，接下来我们通过自己写一个EventBus，让你更容易理解EventBus的原理，下面来看一看实现步骤

1. 定义注解
2. 定义线程模式
3. 订阅方法封装成SubscribeMethod
4. 写一个单例
5. 封装订阅者方法
6. 注册订阅者
7. post发布事件
8. 线程模式处理
9. 执行订阅者方法
10. 销毁注册

定义MySubscrible

首先我们定义一个MySubscrible注解，注解还不知道如何使用的，看我之前写的博客Android 注解（Annotation）的入门与使用（一）和Android 注解（Annotation）的入门与使用（二）

/** * QQ：941556675 * zhy * **/@Target(ElementType.METHOD)@Retention(RetentionPolicy.RUNTIME)public @interface MySubscrible {    ThreadMode threadMode() default ThreadMode.MAIN;}

定义线程模式

/** * QQ：941556675 * zhy * **/public enum  ThreadMode {    MAIN,    BACHGROUND}

订阅方法封装成SubscribeMethod

/** * QQ：941556675 * zhy * **/public class SubscribeMethod {    private Method method;    private ThreadMode threadMode;    //方法里面的参数类型    private Class<?> type;    public SubscribeMethod(Method method, ThreadMode threadMode, Class<?> type) {        this.method = method;        this.threadMode = threadMode;        this.type = type;    }    public Method getMethod() {        return method;    }    public void setMethod(Method method) {        this.method = method;    }    public ThreadMode getThreadMode() {        return threadMode;    }    public void setThreadMode(ThreadMode threadMode) {        this.threadMode = threadMode;    }    public Class<?> getType() {        return type;    }    public void setType(Class<?> type) {        this.type = type;    }}

写一个单例

/** * QQ：941556675 * zhy * **/public class MyEventBus {    private Handler mHandler;    static volatile MyEventBus defaultInstance;    private Map> map;    private ExecutorService executorService;    public static MyEventBus getDefault() {        MyEventBus instance = defaultInstance;        if (instance == null) {            synchronized (MyEventBus.class) {                instance = MyEventBus.defaultInstance;                if (instance == null) {                    instance = MyEventBus.defaultInstance = new MyEventBus();                }            }        }        return instance;    }    public MyEventBus(){     mHandler = new Handler();        map=new HashMap<>();        executorService = Executors.newCachedThreadPool();    } }

封装订阅者方法及注册订阅者

/** * QQ：941556675 * zhy * **/public void register(Object obj){        List subscribeMethods = map.get(obj);        if(subscribeMethods==null){            subscribeMethods = findSubscriberMethods(obj);            map.put(obj,subscribeMethods);        }    }    public List findSubscriberMethods(Object obj){        List list=new ArrayList<>();        Class<?> aClass = obj.getClass();        Method[] declaredMethods = aClass.getDeclaredMethods();        for(Method method:declaredMethods){        //判断该方法是否被MySubscrible注解了            if(method.isAnnotationPresent(MySubscrible.class)){             // 返回该方法的注解在此方法的指定注解类型                MySubscrible annotation = method.getAnnotation(MySubscrible.class);                 // 添加一些校验                Class<?>[] parameterTypes = method.getParameterTypes();                if(parameterTypes.length!=1){                    throw new RuntimeException("方法只能为一个参数");                }                ThreadMode threadMode = annotation.threadMode();                // 生成订阅者方法封装对象                SubscribeMethod methodManager = new SubscribeMethod(method, threadMode, parameterTypes[0]);                list.add(methodManager);            }        }        return list;    }

post发布事件

public void post(final Object obj){        Set