Android开源框架之EventBus（二）

理解了EventBus的源码之后，接下来就仿照实现一个自己的EventBus

一、创建一个TestThreadMode

public enum TestThreadMode {

    MAIN,
    BACKGROUND

}

二、创建一个TestSubscribe注解类

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface TestSubscribe {
     // 默认TestThreadMode.MAIN;
     TestThreadMode threadMode() default TestThreadMode.MAIN; 
     boolean stick() default false;
}

三、SubscribeMethod类封装注解方法等

public class SubscribeMethod {

    private Method method;

    private TestThreadMode threadMode;

    private Class<?> type;

    private boolean stick;

    public SubscribeMethod(Method method, TestThreadMode threadMode, Class<?> type,boolean stick) {
        this.method = method;
        this.threadMode = threadMode;
        this.type = type;
        this.stick = stick;
    }

    public boolean isStick() {
        return stick;
    }

    public void setStick(boolean stick) {
        this.stick = stick;
    }

    public Method getMethod() {
        return method;
    }

    public void setMethod(Method method) {
        this.method = method;
    }

    public TestThreadMode getThreadMode() {
        return threadMode;
    }

    public void setThreadMode(TestThreadMode threadMode) {
        this.threadMode = threadMode;
    }

    public Class<?> getType() {
        return type;
    }

    public void setType(Class<?> type) {
        this.type = type;
    }
}

创建TestEventBus

public class TestEventBus {

    private static volatile TestEventBus testEventBus;
    //保存SubscribeMethod的map集合，是以事件类型为key
    private Map<Object,List<SubscribeMethod>> cacheMap;
    //保存粘性事件
    private Map<Class<?>,Object> stickMap;

    private Handler mHandler;

    private TestEventBus(){
        cacheMap = new HashMap<>();
        mHandler = new Handler();
        stickMap = new HashMap<>();
    }
    //仿EventBus使用单例
    public static TestEventBus getDefault() {
        if(testEventBus == null){
            synchronized (TestEventBus.class){

                if(testEventBus == null){
                    testEventBus = new TestEventBus();
                }
            }
        }
        return testEventBus;
    }

    //注册
    @TargetApi(Build.VERSION_CODES.O)
    public void register(Object obj) {
        List<SubscribeMethod> subscribeMethodList = cacheMap.get(obj);

        if(subscribeMethodList == null) {
            //获取所有的注解方法的封装类
            subscribeMethodList = findSubscribeMethod(obj);
           //将注解信息添加到map中
            cacheMap.put(obj,subscribeMethodList);
        }
        //循环注解封装类集合
        for(SubscribeMethod subscribeMethod : subscribeMethodList){
            //判断是否为粘性事件
            if(subscribeMethod.isStick()){
                //发送粘性事件
                post(stickMap.get(subscribeMethod.getType()));

            }

        }

    }
    
    
    private List<SubscribeMethod> findSubscribeMethod(Object obj) {

        List<SubscribeMethod> subscribeMethodList = new ArrayList<>();
        //获取订阅者的Class类型
        Class<?> clzz = obj.getClass();
        //获取所有注解方法
        Method[] methods = clzz.getDeclaredMethods();

        for(Method method : methods){
            //获取带有TestSubscribe.class注解的方法
            TestSubscribe testSubscribe = method.getAnnotation(TestSubscribe.class);
            if(testSubscribe == null){
                continue;
            }
            //获取方法的参数
            Class<?>[] parameterTypes = method.getParameterTypes();
            //判断参数的个数
            if(parameterTypes.length != 1){
                try {
                    throw new Exception("@Subscribe method must have exactly 1 parameter but has " + parameterTypes.length);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }else{
                //得到注解方法的threadMode
                TestThreadMode testThreadMode = testSubscribe.threadMode();
                //封装注解信息
                SubscribeMethod subscribeMethod = new SubscribeMethod(method,testThreadMode,parameterTypes[0],testSubscribe.stick());
                subscribeMethodList.add(subscribeMethod);
            }

        }

        return subscribeMethodList;
    }

    //发送粘性事件
    public void postStick( Object eventType) {

        stickMap.put(eventType.getClass(),eventType);

    }

   //发送事件
    public void post(final Object eventType) {

        Set<Object> keySet = cacheMap.keySet();

       // keySet.iterator();

        for(final Object obj : keySet){
            //获取注解信息
            List<SubscribeMethod> subscribeMethodList = cacheMap.get(obj);

            for(final SubscribeMethod subscribeMethod : subscribeMethodList){
                //判断注解信息中事件与发送事件是否一致
                if(subscribeMethod.getType().isAssignableFrom(eventType.getClass())){
                    //判断ThreadMode
                    switch (subscribeMethod.getThreadMode()){

                        case MAIN:
                            //主--主
                            if(Looper.myLooper() == Looper.getMainLooper()){
                                invoke(subscribeMethod,obj,eventType);
                            }else{
                                //子--主
                                mHandler.post(new Runnable() {
                                    @Override
                                    public void run() {
                                        invoke(subscribeMethod,obj,eventType);
                                    }
                                });
                            }
                            break;

                        case BACKGROUND:
                            //主---子 ExecutorService
                            //子---子
                            break;

                    }
                }
            }
        }
    }

    private void invoke(SubscribeMethod subscribeMethod, Object obj, Object eventType) {
       //调用注解方法，发送消息
        Method method = subscribeMethod.getMethod();
        try {
            method.invoke(obj,eventType);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

    }
}

这样一个简单的自定义EventBus就完了。