@interface Subscribe分析
前面参考的代码，存放在（use_little_demo中的 eventbus3test）
https://github.com/2954722256/use_little_demo
我们通过eventbus3的注解
用ctrl+鼠标左键， 跟进去，可以看见
@interface Subscribe
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
public @interface Subscribe {
ThreadMode threadMode() default ThreadMode.POSTING;
/**
* If true, delivers the most recent sticky event (posted with
* {@link EventBus#postSticky(Object)}) to this subscriber (if event available).
*/
boolean sticky() default false;
/** Subscriber priority to influence the order of event delivery.
* Within the same delivery thread ({@link ThreadMode}), higher priority subscribers will receive events before
* others with a lower priority. The default priority is 0. Note: the priority does *NOT* affect the order of
* delivery among subscribers with different {@link ThreadMode}s! */
int priority() default 0;
}
我们可以看见，和我们自己例子类似的结构
这里多了个@Documentd， 这个也提到过，文档相关的，我们可以忽略
简单扯淡
通过
- @Retention(RetentionPolicy.RUNTIME)
- @Target({ElementType.METHOD})
我们可以知道，是放在方法上面使用的
（我们上一篇是放在类上面使用的，和这个不同的是，只是放在方法前面使用）
也就是上图使用的形式
这里接口，有3个方法
我们可以发现，对应的一些配置，例如
其实，都是通过注解传入值的
（上一篇，我们也有对应的传值例子，具体可以参考）
简单复习
第一篇，我们提到过，有4中模式
也就是这里配置的threadMode()返回类型ThreadMode
我们来看一下ThreadMode类
ThreadMode
/**
* Each event handler method has a thread mode, which determines in which thread the method is to be called by EventBus.
* EventBus takes care of threading independently from the posting thread.
*
* @see EventBus#register(Object)
* @author Markus
*/
public enum ThreadMode {
/**
* Subscriber will be called in the same thread, which is posting the event. This is the default. Event delivery
* implies the least overhead because it avoids thread switching completely. Thus this is the recommended mode for
* simple tasks that are known to complete is a very short time without requiring the main thread. Event handlers
* using this mode must return quickly to avoid blocking the posting thread, which may be the main thread.
*/
POSTING,
/**
* Subscriber will be called in Android's main thread (sometimes referred to as UI thread). If the posting thread is
* the main thread, event handler methods will be called directly. Event handlers using this mode must return
* quickly to avoid blocking the main thread.
*/
MAIN,
/**
* Subscriber will be called in a background thread. If posting thread is not the main thread, event handler methods
* will be called directly in the posting thread. If the posting thread is the main thread, EventBus uses a single
* background thread, that will deliver all its events sequentially. Event handlers using this mode should try to
* return quickly to avoid blocking the background thread.
*/
BACKGROUND,
/**
* Event handler methods are called in a separate thread. This is always independent from the posting thread and the
* main thread. Posting events never wait for event handler methods using this mode. Event handler methods should
* use this mode if their execution might take some time, e.g. for network access. Avoid triggering a large number
* of long running asynchronous handler methods at the same time to limit the number of concurrent threads. EventBus
* uses a thread pool to efficiently reuse threads from completed asynchronous event handler notifications.
*/
ASYNC
}
我们通过配置，就可以让 EventBus类， 拿到具体的类型了
在看一下sticky()
我们默认不配置的时候，返回false（代码中可以知道）
我们例子里面，有一个地方，
Activity还没有启动，只要配置sticky = true
再通过postSticky去传值，就可以传递到没有启动的Activity
priority()
我们暂时还没有用上，
我们通过看文档（或者对线程熟悉，名字就可以猜出来），
可以了解到和对应的优先级有关
这里先不扯了
简单总结
@interface Subscribe
还是挺简单的，就是3个方法，可以在配置中，传递3中参数
（每个都有默认值，所以也可以不配置对应的值）
拿到值以后，和上一篇一样，
应该有一个地方可以拿到对应的值，再做处理
代码地址
前面参考的代码，存放在（use_little_demo中的 eventbus3test）
https://github.com/2954722256/use_little_demo
下一篇我们可以了解Eventbus3代码分析（五）：getDefault()，register和EventBusBuilder等
