EventBus is a publish/subscribe event bus for Android and Java.

EventBus...

• simplifies the communication between components
  • decouples event senders and receivers
  • performs well with Activities, Fragments, and background threads
  • avoids complex and error-prone dependencies and life cycle issues
• makes your code simpler
• is fast
• is tiny (~60k jar)
• is proven in practice by apps with 1,000,000,000+ installs
• has advanced features like delivery threads, subscriber priorities, etc.

1. Define events:

   public static class MessageEvent { /* Additional fields if needed */ }

2. Prepare subscribers: Declare and annotate your subscribing method, optionally specify a thread mode:

   @Subscribe(threadMode = ThreadMode.MAIN)  
   public void onMessageEvent(MessageEvent event) {
       // Do something
   }

   Register and unregister your subscriber. For example on Android, activities and fragments should usually register according to their life cycle:

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

3. Post events:

    EventBus.getDefault().post(new MessageEvent());

Read the full getting started guide.

There are also some examples.

Note: we highly recommend the EventBus annotation processor with its subscriber index. This will avoid some reflection related problems seen in the wild.

Available on Maven Central.

Android projects:

implementation("org.greenrobot:eventbus:3.3.1")

Java projects:

implementation("org.greenrobot:eventbus-java:3.3.1")

<dependency>
    <groupId>org.greenrobot</groupId>
    <artifactId>eventbus-java</artifactId>
    <version>3.3.1</version>
</dependency>

If your project uses R8 or ProGuard this library ships with embedded rules.

For more details please check the EventBus website. Here are some direct links you may find useful:

Features

Documentation

Changelog

FAQ

Copyright (C) 2012-2021 Markus Junginger, greenrobot (https://greenrobot.org)

EventBus binaries and source code can be used according to the Apache License, Version 2.0.

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