Android Passing an event


Example

This example describes passing an event using the Otto Event Bus.

To use the Otto Event Bus in Android Studio you have to insert the following statement in your modules gradle file:

dependencies {
    compile 'com.squareup:otto:1.3.8'
}

The event we'd like to pass is a simple Java object:

public class DatabaseContentChangedEvent {
    public String message;

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

We need a Bus to send events. This is typically a singleton:

import com.squareup.otto.Bus;

public final class BusProvider {
    private static final Bus mBus = new Bus();

    public static Bus getInstance() {
        return mBus;
    }

    private BusProvider() {
    }
}

To send an event we only need our BusProvider and it's post method. Here we send an event if the action of an AsyncTask is completed:

public abstract class ContentChangingTask extends AsyncTask<Object, Void, Void> {

    ...

    @Override
    protected void onPostExecute(Void param) {
        BusProvider.getInstance().post(
            new DatabaseContentChangedEvent("Content changed")
        );
    }
}