CODEWITHSUNDEEP
javaandroid
user2990037
user2990037

Reputation: 397

Android - Multifunction Asynctask returning data

I'm having some trouble with my coursework for my mobile programming module.

Basically I've extended Asynctask which executes a php script which accesses my MYSQL database depending on the input. Now one of the functions which is executed requires me to return data from the script to another class. The class order is so:

MainClass -> HelperClass -> NetworkClass(AsyncTask)

MainClass executes the HelperClass function 'QueryDatabase' which then creates data needed by the php script, this data is then passed to NetworkClass.

NetworkClass then executes the database query and stores the received data (public var) HelperClass then pulls the data from the NetworkClass. MainClass then pulls the data from the HelperClass and its then processed.

Currently this is the best way I can think to do this as I want to keep my NetworkClass dynamic. However the problem is that MainClass does not wait for NetworkClass to execute fully before trying to pull the data and so processing does not complete.

Whats the best way to do this? Can I put a delay or something between executing the database query in MainClass and pulling the data?

Hope this makes sense.

Not too sure what code to post as I have a lot. Sorry about that.

Upvotes: 2

Views: 77

Answers (2)

WIllJBD
WIllJBD

Reputation: 6154

No, never use some random delay to assume that is how long it takes for a request to complete.

What you should do is implement an interface that is used as a callback for the oncomplete of the async task. You implement this interface where you need to know when and what is returned, and then pass in the interface object to the asynctask to be called in the oncomplete method.

One other thing to think about, you may want to have your database work on a background thread as well if it can be intensive.

here is what this might look like

    class EZAsyncTask extends AsyncTask<Void, Void, String>
    {

        private AsyncTaskListener listener;

        public EZAsyncTask(AsyncTaskListener listener)
        {
            super();
            this.listener = listener;
        }

        @Override
        protected String doInBackground(Void... params)
        {
            //somethign to do
            return null;
        }

        @Override
        protected void onPostExecute(String result)
        {
            super.onPostExecute(result);
            listener.onCompletion(result);
        }

        public interface AsyncTaskListener
        {
            public void onCompletion(String result);
        }

    }

the usage in your activity or whatever might look like this on a per use basis

EZAsyncTask ezTask = new EZAsyncTask(new AsyncTaskListener() {
    @Override
    public void onCompletion(String result)
    {
        // TODO handle response
    }
    });
ezTask.execute();

or you could just let your class/activity implement it, like you might let your activity implement an OnClickListener

Another way you could do this is through Handler, and there are other patterns you could do. But I much prefer to do it this way. easy, quick, clean.

Upvotes: 2

Vincent Cantin
Vincent Cantin

Reputation: 17292

The piece of code that you have in your MainClass which pulls the result, it should be asynchronous. There is no point in having it doing an active wait for the result, as it will stall the thread on which it is executing.

This is the parttern I am usually following:

private class NetworkAsyncTask extends AsyncTask<Foo, Void, Bar> {

  @Override
  protected Bar doInBackground(Foo... foos) {
    // Use the "foos" to fetch a "bar" from your network.
  }

  @Override
  protected void onPostExecute(Bar bar) {
    // Put here your result handling code,
    // don't leave it in the waiting state on the thread used in your MainClass.
  }
}

Upvotes: 0

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