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greenrobot /EventBus

Event bus for Android and Java that simplifies communication between Activities, Fragments, Threads,...

22.7K Stars 4.5K Forks Last release: 6 months ago (V3.2.0) Apache License 2.0 507 Commits 7 Releases

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

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  • 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.

EventBus in 3 steps

  1. Define events:

public static class MessageEvent { /\* Additional fields if needed \*/ }
  1. 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: ```java 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. Add EventBus to your project ----------------------------[![](]( on [Maven Central]( Via Gradle: ```gradle implementation 'org.greenrobot:eventbus:3.2.0'

Via Maven:


R8, ProGuard

If your project uses R8 or ProGuard add the following rules:

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

# And if you use AsyncExecutor:
-keepclassmembers class * extends org.greenrobot.eventbus.util.ThrowableFailureEvent {

Homepage, Documentation, Links

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





How does EventBus compare to other solutions, like Otto from Square? Check this comparison.


Copyright (C) 2012-2020 Markus Junginger, greenrobot (

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

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