Add description and example to README

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Kai S. K. Engelbart 2020-09-03 10:05:00 +02:00
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# event-bus
# Event Bus
This library allows passing events between different objects without them having a direct reference to each other.
Any class can be made an event by implementing the `IEvent` interface.
Using an instance of the `EventBus` class, an instant of the event class can be dispatched.
This means that it will be forwarded to all listeners registered for it at the event bus.
To listen to events, register event handling methods using the `Event` annotation.
For this to work, the method must have a return type of `void` and declare a single parameter of the desired event type.
Additionally, the class containing the method must implement the `EventListener` interface.
Lets look at a simple example: we declare the empty class `SimpleEvent` that implements `IEvent` and can thus be used as an event.
```java
import dev.kske.eventbus.IEvent;
public class SimpleEvent implements IEvent {}
```
Next, an event listener for the `SimpleEvent` is declared:
```java
import dev.kske.eventbus.*;
public class SimpleEventListener implements EventListener {
public SimpleEventListener() {
EventBus eventBus = new EventBus();
// Register this listener at the event bus
eventBus.register(this);
// Dispatch a SimpleEvent
eventBus.dispatch(new SimpleEvent());
}
@Event
private void onSimpleEvent(SimpleEvent event) {
System.out.println("SimpleEvent received!");
}
}
```
In this case, an event bus is created and used locally. In a more sophisticated example the class would acquire an external event bus that is used by multiple classes.