how to catch a out of memory Exception in AsyncTask

Question

My android application connect do an external database using a Web Service. In one case I have Enormous number of data, and I got out of memory exception:

09-09 20:05:59.441: ERROR/dalvikvm(4688): Out of memory: Heap Size=15751KB, Allocated=14962KB, Bitmap Size=687KB
09-09 20:05:59.451: WARN/dalvikvm(4688): threadid=23: thread exiting with uncaught exception (group=0x4001e390)
09-09 20:05:59.462: ERROR/AndroidRuntime(4688): Uncaught handler: thread AsyncTask #5 exiting due to uncaught exception
09-09 20:05:59.731: ERROR/AndroidRuntime(4688): java.lang.RuntimeException: An error occured while executing doInBackground()
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at android.os.AsyncTask$3.done(AsyncTask.java:200)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at java.util.concurrent.FutureTask.run(FutureTask.java:137)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at java.lang.Thread.run(Thread.java:1102)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688): Caused by: java.lang.OutOfMemoryError
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at java.lang.AbstractStringBuilder.enlargeBuffer(AbstractStringBuilder.java:97)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at java.lang.AbstractStringBuilder.append0(AbstractStringBuilder.java:142)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at java.lang.StringBuilder.append(StringBuilder.java:124)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at org.json.JSONTokener.nextString(JSONTokener.java:252)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at org.json.JSONTokener.nextValue(JSONTokener.java:316)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at org.json.JSONObject.<init>(JSONObject.java:204)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at org.json.JSONTokener.nextValue(JSONTokener.java:319)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at org.json.JSONObject.<init>(JSONObject.java:204)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at org.json.JSONTokener.nextValue(JSONTokener.java:319)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at org.json.JSONArray.<init>(JSONArray.java:116)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at org.json.JSONArray.<init>(JSONArray.java:150)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at se.softwerk.timelog.activity.ViewActivity.setTasks(ViewActivity.java:219)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at se.softwerk.timelog.activity.ViewActivity.fetchTasks(ViewActivity.java:133)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at se.softwerk.timelog.activity.ViewActivity.access$9(ViewActivity.java:110)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at se.softwerk.timelog.activity.ViewActivity$LoadingDataFromServer.doInBackground(ViewActivity.java:420)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at se.softwerk.timelog.activity.ViewActivity$LoadingDataFromServer.doInBackground(ViewActivity.java:1)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at android.os.AsyncTask$2.call(AsyncTask.java:185)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
09-09 20:05:59.731: ERROR/AndroidRuntime(4688):     ... 4 more

This is my class:

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

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

        @Override
        protected void onPostExecute(Void result) {
            try {
                ListView lv = (ListView) main_activity.findViewById(R.id.listTask);
                lv.setAdapter(new TaskAdapter(main_activity));
                progress.dismiss();
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }
        }

        @Override
        protected Void doInBackground(Void... params) {
            try {
                fetchTasks();
            } catch (Exception e) {      //DOES NOT WORK
                progress.dismiss();
                Toast.makeText(ViewActivity.this, "Enormous number of data, select smaller criteria", Toast.LENGTH_SHORT).show();
                finish();
            }
            return null;
        }
    }

How can I catch this Exception in doInBackground? My current trying does not work.

Answer 1

try {
    ...
} catch (Exception e) {  // "catch all subclasses of java.lang.Exception"
    ...
}

However, OutOfMemoryError inherits from java.lang.Error and not java.lang.Exception and they both inherit from java.lang.Throwable. You can only throw instances of subclasses of java.lang.Throwable in java so you can catch any error or exception with this:

try {
    ...
} catch (Throwable t) {  // "catch all subclasses of java.lang.Throwable"
    ...
}

Answer 2

OutOfmemoryError doesn't extends Exception, this is why you don't catch it.

This code should work.

try
{
    fetchTasks();       
}
catch(OutOfMemoryError e)
{
    // do something     
}