Why does this background task fail with a fatal exception?

Question

The following code in my MainActivity is failing with a fatal exception in the overridden doInBackground() method:

public class MainActivity extends ActionBarActivity {

    . . .

    public void onFetchBtnClicked(View v){
        if(v.getId() == R.id.FetchBtn){
            Toast.makeText(getApplicationContext(), "You mashed the button, dude.", Toast.LENGTH_SHORT).show();
            new NetworkTask().execute();
        }
    }

    public static class NetworkTask extends AsyncTask<String, Void, HttpResponse> {

        @Override
        protected HttpResponse doInBackground(String... params) {
            String link = params[0];
            HttpGet request = new HttpGet("http://localhost:28642/api/deliveries/Count");
            AndroidHttpClient client = AndroidHttpClient.newInstance("Android");
            try {
                return client.execute(request);
            } catch (IOException e) {
                e.printStackTrace();
                return null;
            } finally {
                client.close();
            }
        }

        @Override
        protected void onPostExecute(HttpResponse result) {
            FileOutputStream f = null;
            //Do something with result
            if (result != null)
                    /* result.getEntity().writeTo(new FileOutputStream(f)); */
                try {
                    result.getEntity().writeTo(f);
                } catch (IOException e) {
                    e.printStackTrace();
                }
        }

    }

The specific exception messages, with a smidgin of pre-exception context follows:

03-31 18:04:26.350    1401-1401/hhs.app I/Choreographer﹕ Skipped 33 frames!  The application may be doing too much work on its main thread.
03-31 18:05:00.030    1401-1420/hhs.app W/dalvikvm﹕ threadid=12: thread exiting with uncaught exception (group=0xb2a7aba8)
03-31 18:05:00.250    1401-1420/hhs.app E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #1
    Process: hhs.app, PID: 1401
    java.lang.RuntimeException: An error occured while executing doInBackground()
            at android.os.AsyncTask$3.done(AsyncTask.java:300)
            at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
            at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
            at java.util.concurrent.FutureTask.run(FutureTask.java:242)
            at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
            at java.lang.Thread.run(Thread.java:841)
     Caused by: java.lang.ArrayIndexOutOfBoundsException: length=0; index=0
            at hhs.app.MainActivity$NetworkTask.doInBackground(MainActivity.java:68)
            at hhs.app.MainActivity$NetworkTask.doInBackground(MainActivity.java:64)
            at android.os.AsyncTask$2.call(AsyncTask.java:288)
            at java.util.concurrent.FutureTask.run(FutureTask.java:237)
            at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
            at java.lang.Thread.run(Thread.java:841)

What's the problem with this - it fails at the git-go of doInBackground(). Is my URL "bad" due to the whacks (in C#, I would use a verbatim string), or...?

UPDATE

I removed the problematic line, yet it still fails, throwing an IOException.

I had actually switched gears to completely different code as can be seen here [Why am I getting, "incompatible types: Object cannot be converted to String" with this? (which was throwing NetworkOnMainThreadException), but when that failed I decided to give this code another chance, but the "catch (IOException e) " block is entered.

Does anybody know why?

Answer 1

You forgot to pass any params to your AsyncTask here:

 new NetworkTask().execute();

That is why your array is empty here:

 String link = params[0];

==> pass a parameter while executing the AsyncTask:

 new NetworkTask().execute(someLink); //execute AsyncTask with one param

Update: in fact seems like you don't do anything with String link in the doInBackground method. So maybe you can just get rid of that line?

Answer 2

This exception:

Caused by: java.lang.ArrayIndexOutOfBoundsException: length=0; index=0

is telling you that you are accessing an empty array at index 0, in this line:

protected HttpResponse doInBackground(String... params) {
     String link = params[0];

nota that after the assignment you dont use the link variable anywhere (nor the params).