EventBus 3

EventBus 是一个基于观察者模式的事件发布/订阅框架

资料

Github
Documentation

Eventbus
老司机教你 “飙” EventBus 3

设置

导入

• 配置模组的 build.gradle

android {
    defaultConfig {
        javaCompileOptions {
            annotationProcessorOptions {
                arguments = [ eventBusIndex : 'com.example.myapp.MyEventBusIndex' ] // 索引全名
            }
        }
    }
}

dependencies {
    compile 'org.greenrobot:eventbus:3.0.0'
    annotationProcessor 'org.greenrobot:eventbus-annotation-processor:3.0.1'
}

初始化

// 设置为默认属性
EventBus.builder().addIndex(new MyEventBusIndex()).installDefaultEventBus();
EventBus eventBus = EventBus.getDefault(); // 设置完后，使用默认即可

// 或者在使用时再设置
EventBus eventBus = EventBus.builder().addIndex(new MyEventBusIndex()).build();

// 如果库中有EventBusIndex，需要多次添加
EventBus eventBus = EventBus.builder()
    .addIndex(new MyEventBusAppIndex())
    .addIndex(new MyEventBusLibIndex())
    .build();

混淆

-keepattributes *Annotation*
-keepclassmembers class ** {
    @org.greenrobot.eventbus.Subscribe <methods>;
}
-keep enum org.greenrobot.eventbus.ThreadMode { *; }

# Only required if you use AsyncExecutor
-keepclassmembers class * extends org.greenrobot.eventbus.util.ThrowableFailureEvent {
    <init>(java.lang.Throwable);
}

基本用法

定义事件Event

public class MessageEvent {

    public final String message;

    public MessageEvent(String message) {
        this.message = message;
    }
}

注册

订阅之前需要注册，activities和fragments一般在 onStart/onStop 中调用

@Override
public void onStart() {
    super.onStart();
    EventBus.getDefault().register(this);
}

@Override
public void onStop() {
    EventBus.getDefault().unregister(this);
    super.onStop();
}

订阅

四种线程模式，ThreadMode: POSTING/MAIN/BACKGROUND/ASYNC

// 在发送事件的线程调用，同步处理
@Subscribe
public void handleSomethingElse(SomeOtherEvent event) {
    doSomethingWith(event);
}

// 主线程调用
@Subscribe(threadMode = ThreadMode.MAIN)
public void onMessageEvent(MessageEvent event) {
    Toast.makeText(getActivity(), event.message, Toast.LENGTH_SHORT).show();
}

// 子线程调用，非主线程则直接调用，主线程则开单线程调用
@Subscribe(threadMode = ThreadMode.BACKGROUND)
public void onMessage(MessageEvent event){
    saveToDisk(event.message);
}

// 异步调用，使用线程池在不同的线程调用
@Subscribe(threadMode = ThreadMode.ASYNC)
public void onMessage(MessageEvent event){
    backend.send(event.message);
}

发送

任意地方发送事件，匹配的事件订阅方法会接收事件

EventBus.getDefault().post(new MessageEvent("Hello everyone!"));

优先级

@Subscribe(priority = 1); // 优先级，默认为0
public void onEvent(MessageEvent event) {

  // 取消传递，只能运行在ThreadMode.PostThread
  EventBus.getDefault().cancelEventDelivery(event);
}

粘性事件 Sticky Event

事件发出后一直保存在内存中，订阅方法在之后注册也能完成订阅

用法

EventBus.getDefault().postSticky(new MessageEvent("Hello everyone!"));

@Override
public void onStart() {
    super.onStart();
    EventBus.getDefault().register(this);
}

@Subscribe(sticky = true, threadMode = ThreadMode.MAIN)
public void onEvent(MessageEvent event) {
    textField.setText(event.message);
}

@Override
public void onStop() {
    EventBus.getDefault().unregister(this);
    super.onStop();
}

取消事件

MessageEvent stickyEvent = EventBus.getDefault().getStickyEvent(MessageEvent.class);
if(stickyEvent != null) {
    EventBus.getDefault().removeStickyEvent(stickyEvent);
}

MessageEvent stickyEvent = EventBus.getDefault().removeStickyEvent(MessageEvent.class);
if(stickyEvent != null) {
}

配置

无订阅时无日志

EventBus eventBus = EventBus.builder()
    .logNoSubscriberMessages(false)
    .sendNoSubscriberEvent(false)
    .build();

抛异常

EventBus eventBus = EventBus.builder().throwSubscriberException(true).build();

修改默认

EventBus.builder().throwSubscriberException(BuildConfig.DEBUG).installDefaultEventBus();

异步执行器 AsyncExecutor

• AsyncExecutor就像一个带异常处理的线程池
• 异常被自动捕获包裹成ThrowableFailureEvent并发送

用法

AsyncExecutor.create()  // 在 Application 中创建保存实例
        .execute(new AsyncExecutor.RunnableEx() {
                     @Override
                     public void run() throws LoginException {
                         // 不需要捕获异常
                         remote.login();
                         EventBus.getDefault().postSticky(new LoggedInEvent());
                     }
                 }
        );
}

@Subscribe(threadMode = ThreadMode.MAIN)
public void handleLoginEvent(LoggedInEvent event) {
}

@Subscribe(threadMode = ThreadMode.MAIN)
public void handleFailureEvent(ThrowableFailureEvent event) {
  // 处理异常
}

自定义

• AsyncExecutor.builder()
• 可定义EventBus实例、线程池、失败事件类、作用域