Question

I am connecting from my Android app to a RESTful Web Service in Java. I am using AsyncTask to fetch the data. It works perfectly for normal amount of data. but when I have a huge amount of data, an Exception happens in the Android app. I tried to catch this exception, but I couldn’t:

private class LoadingDataFromServer extends AsyncTask<Void, Void, Void> {

        private boolean outOfMemory = false;

        @Override
        public void onPreExecute() {
            progress = ProgressDialog.show(main_activity, null,"Loading ...", true);
        }

        @Override
        protected void onPostExecute(Void result) {
            if(outOfMemory) {
                Toast.makeText(StatisticActivity.this, "Out of memory, select smaller criteria", Toast.LENGTH_SHORT).show();
                finish();
            }
            else
                setListView();
            try {
                progress.dismiss();
            } catch (Exception e) { }
        }

        @Override
        protected Void doInBackground(Void... params) {
            TextView txtProject = (TextView) main_activity.findViewById(R.id.project);
            txtProject.setBackgroundColor(Color.DKGRAY);
            txtProject.setText(project);

            TextView label = (TextView) main_activity.findViewById(R.id.label);
            label.setText(R.string.deliverable);
            try {
            loadStatistic();
            } catch (OutOfMemoryError e) {
                outOfMemory = true;
                progress.dismiss();
            } catch (RuntimeException e) {
                outOfMemory = true;
                progress.dismiss();
            } catch (Exception e) {
                outOfMemory = true;
                progress.dismiss();
            }
            return null;
        }
    }

This is the error I got:

10-14 22:24:10.952: ERROR/AndroidRuntime(4179): Uncaught handler: thread AsyncTask #3 exiting due to uncaught exception
10-14 22:24:10.962: ERROR/AndroidRuntime(4179): java.lang.RuntimeException: An error occured while executing doInBackground()
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     at android.os.AsyncTask$3.done(AsyncTask.java:200)
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     at java.util.concurrent.FutureTask.run(FutureTask.java:137)
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     at java.lang.Thread.run(Thread.java:1102)
10-14 22:24:10.962: ERROR/AndroidRuntime(4179): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     at android.os.Handler.<init>(Handler.java:121)
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     at android.widget.Toast.<init>(Toast.java:68)
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     at android.widget.Toast.makeText(Toast.java:231)
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     at se.softwerk.timelog.statistic.StatisticActivity$LoadingDataFromServer.doInBackground(StatisticActivity.java:301)
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     at se.softwerk.timelog.statistic.StatisticActivity$LoadingDataFromServer.doInBackground(StatisticActivity.java:1)
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     at android.os.AsyncTask$2.call(AsyncTask.java:185)
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
10-14 22:24:10.962: ERROR/AndroidRuntime(4179):     ... 4 more

The exception is happening in doInBackground, but my exception handeling did not work. Can you help me?

Answer 1

You should call any UI-related code from within onPreExecute(), onProgressUpdate(Progress... values) or onPostExecute(Result result) (which run in main thread, the UI thread), and use doInBackground(Params... params) only to perform CPU-intensive operations.

Calling publishProgress(Progress... values) within doInBackground(Params... params) will send data to onProgressUpdate(Progress... values), where you can use it to update the UI.