As of 15/2/2012 I have yet to find a good explanation to nor a reason why this does not work. The closest to a solution is to use the traditional Thread approach, but then why include a class that does not (seem to) work in the Android SDK?
Evenin' SO!
I have an AsyncTask subclass:
// ParseListener had a callback which was called when an item was parsed in a
// RSS-xml, but as stated further down it is not used at all right now.
private class xmlAsync extends AsyncTask<String, RSSItem, Void> implements ParseListener
That is executed like this:
xmlAsync xmlThread = new xmlAsync();
xmlThread.execute("http://www.nothing.com");
Now this subclass has run into a little error. Previously it did some xml-parsing, but when I noticed that it's doInBackground() wasn't called I stripped it down, line by line, finally ending up with just this:
@Override
protected Void doInBackground(String... params)
{
Log.v(TAG, "doInBackground");
return null;
}
Which, for some reason, logged nothing. However, I added this:
@Override
protected void onPreExecute()
{
Log.v(TAG, "onPreExecute");
super.onPreExecute();
}
And that line is indeed logged when executing the thread. So somehow onPreExecute() is called but not doInBackground(). I have another AsyncTask running in the background at the same time which works just fine.
I'm currently running the app on an emulator, SDK Version 15, Eclipse, Mac OS X 10.7.2, close to the North Pole.
EDIT:
@Override
protected void onProgressUpdate(RSSItem... values) {
if(values[0] == null)
{
// activity function which merely creates a dialog
showInputError();
}
else
{
Log.v(TAG, "adding "+values[0].toString());
_tableManager.addRSSItem(values[0]);
}
super.onProgressUpdate(values);
}
_tableManager.addRSSItem() more or less adds a row to a SQLiteDatabase, initialized with the activity's context. publishProgress() is called by the Interface ParseListener's callback. However, since I don't even do anything except log.v in doInBackground() I first found this unnecessary to even bring up.
EDIT 2:
Alright, just to be perfectly clear, this is the other AsyncTask, executing in the same activity and working perfectly fine.
private class dbAsync extends AsyncTask<Void, RSSItem, Void>
{
Integer prevCount;
boolean run;
@Override
protected void onPreExecute() {
run = true;
super.onPreExecute();
}
@Override
protected Void doInBackground(Void... params) {
// TODO Auto-generated method stub
run = true;
prevCount = 0;
while(run)
{
ArrayList<RSSItem> items = _tableManager.getAllItems();
if(items != null)
{
if(items.size() > prevCount)
{
Log.v("db Thread", "Found new item(s)!");
prevCount = items.size();
RSSItem[] itemsArray = new RSSItem[items.size()];
publishProgress(items.toArray(itemsArray));
}
}
SystemClock.sleep(5000);
}
return null;
}
@Override
protected void onProgressUpdate(RSSItem... values) {
ArrayList<RSSItem> list = new ArrayList<RSSItem>();
for(int i = 0; i < values.length; i++)
{
list.add(i, values[i]);
}
setItemsAndUpdateList(list);
super.onProgressUpdate(values);
}
@Override
protected void onCancelled() {
run = false;
super.onCancelled();
}
}
EDIT 3:
Sigh, sorry I'm bad at asking questions. But here is the initialization of the Tasks.
xmlAsync _xmlParseThread;
dbAsync _dbLookup;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
_dbLookup = new dbAsync();
_dbLookup.execute();
_xmlParseThread = new xmlAsync();
_xmlParseThread.execute("http://www.nothing.com", null);
}
