Activities interactions in Android

I am working on an Application that require some interaction between two activities, and I am not sure of what is the best way to achieve it:

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• One of the Activities is a "Logbook" (Just a ListView that displays a bunch of events).
• The other Activity allows the user to create the events, that will be sent (and displayed in the Logbook).

How do I notify my Logbook Activity when a new Event is ready to be added? Also, where should I add the event to the database? From the Logbook Activity, when I add it to the ListView, or from the NewEvents Activity, as soon as it's ready?

Thanks!

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Ok, I found how to do it, using a BroadcastReceiver:

In my Logbook activity, I just set up a new custom receiver onCreate():

 public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_logbook);
        registerReceiver(new EventReceiver(this), new IntentFilter("SEND_NEW_EVENT"));

Now, I can make the calls in my newEventActivity:

public void sendToLogbook(int eventId){
        Intent i = new Intent("SEND_NEW_EVENT");
        i.putExtra("newEvent", this.newEvents[eventId]);
        sendBroadcast(i);   
    }

Of course, I had to create my CustomReceiver Class, and override the onReceive() method to do what I want:

public class EventReceiver extends BroadcastReceiver {

    private ActivityLogbook activity;

    public EventReceiver(ActivityLogbook activity) {
        this.activity = activity;
    }

    public void onReceive(Context context, Intent i) {
        this.activity.addToReport((Event)i.getParcelableExtra("newEvent"));
    }
}

It works great so far, but if you do have comments/concerns about this, please tell me!

Thank you!

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If I recall cporrectly the Notepad project which is included in the android sdk and is also part of the tutorials online is a good examaple which should satisfy your needs.

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To borrow from MV-* (Model-View-something or other) patterns, separate your idea of the Model (in this case, your Event objects) and what is displaying them (the View, or in your case an Activity) and it'll become more clear.

If you have your events somewhere global where all activities can interact with them, then you can work with the model and display the model from wherever and however you choose.

One simple suggestion is have a class (EventController or something like that) that allows you to interact with the Events collection, and make it available through a derived Application class. I can explain further if that doesn't make sense. I have a pattern I use in my Android apps whereby all Activity classes have access to a custom global Application instance, so my model is a model and can be accessed by whatever Activities I want to have access.

This is merely one approach, and as always, there are many that may suit your needs.

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One possibility would be:

• The ListActivity gets all the data each time it is resumed and updates the ListView accordingly
• The NewEventActivity does all the job of storing the Event and simply finishes

You can improve it a bit more:

• The ListActivity gets all the data when it starts
• The ListActivity starts the NewEventActivity expecting a OK/CANCELLED result
• The NewEventActivity does all the job of storing the Event and returns a result saying OK or CANCELLED
• Depending on the result it gets from the NewEventActivity, ListActivity reloads its data or not