How does one implement an asynchronous http-post request in android?

Question

I would like to implement the following simple pattern in an android app:

1. Activity A starts activity B
2. In activity B the user fills out a simple form F, then hits submit
3. Activity B then starts an AsyncTask C that posts F to a url, and immediately returns to Activity A
4. Back in activity A, the user continues with business as usual while C is still working. But once C is complete, the user should be notified, in particular if the result was a failure.

The problem I have is with steps 3 and 4. Since C is started by B, how can A get notified? Hmm, not sure if this is clear to anyone but me ...

Anyway, right now I am stuck with a solution where step 3 instead looks like this:

3". Activity B returns the content of the form to activity A. A then starts AsyncTask C to post the form and continues as usual.

But it just seems a bit unnecessary that A also needs to handle the form, it should just be B's responsibility. Any other ideas or solutions out there?

Answer 1

Why not have B acquire the information needed to run the task, then pass that back to A? The onPreExecute() and onPostExecute() happen in the main thread of Activity A.

Never mind, I just saw that in your description. But yes - B handles it all - A just submits the data to the URL.

Answer 2

I would use a broadcast reciever. http://d.android.com/reference/android/content/BroadcastReceiver.html

In Activity B

Intent broadcastIntent = new Intent("com.yourapppackage.BROADCAST");
broadcastIntent.putExtra("myExtras", myExtras.extra); // Put your results in here
sendBroadcast(broadcastIntent);

Fire this from onPostExecute of your AsyncTask.

In your application manifest add an intent filter to your activity A entry http://developer.android.com/guide/topics/manifest/intent-filter-element.html

<activity android:name=".A"
>
    <intent-filter>
        <action android:name="com.yourapppackage.BROADCAST" />
    </intent-filter>
</activity>

Register a BroadcastReceiver in Activity A http://developer.android.com/reference/android/content/BroadcastReceiver.html

// Set up a handler and a broadcast reciever
private final Handler mHandler = new Handler();
private final BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {
    @Override
        public void onReceive(Context context, Intent intent) {
            // Handle reciever
            String mAction = intent.getAction();

            if(mAction.equals("com.yourapppackage.BROADCAST")) {
            // Do something with the results - intent.getExtras();
        }
    }
}

// Register a reciever
IntentFilter myRecieverIntentFilter = new IntentFilter();
myRecieverIntentFilter.addAction("com.yourapppackage.BROADCAST");
this.registerReceiver(mIntentReceiver, myRecieverIntentFilter, null, mHandler);