从适配器（getView）启动的AsyncTask更新TextView

Question

I'm having a strange problem updating a TextView from an AsynTask. In the getView function of my adapter I launch an AsyncTask in order to calculate a number and show it on the screen.

The problem is that the getView function is called several times for a single item, thus is calculating several times the numbers I want to show, what is not very efficient.

I've been investigated and realized that whenever I try to limit the number os calls to the AsyncTask, the number is not shown on screen (with no error messages or exceptions)

public View getView(int position, View convertView, ViewGroup parent) {
    LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View rowView = inflater.inflate(R.layout.category_item, null);
    TextView tvCategory = (TextView) rowView.findViewById(R.id.tvCategory);
    TextView tvUnreadNews = (TextView) rowView.findViewById(R.id.tvUnreadNews);

    Category cat = mCategoriesList.get(position);
    tvCategory.setText(cat.getName());
    if(!cat.isInitialized()) //<-- If I delete this line it works, but inefficienly, as the AsyncTask is launched many times repeatedly
    {
            cat.setIsInitialized(true)
        new GetNewsForCategoryTask(cat, tvUnreadNews, mContext).execute(cat.getId());
    }
    return rowView;
}

This is the AsyncTask. Updates the TextView properly when is calling repeatedly, but does not update the value when called only once for category:

public class GetNewsForCategoryTask extends AsyncTask<String, Integer, JSONArray>{

private Context mContext;
private String mCategoryId;
private TextView mTvUnread;
private Category mCategory;

public GetNewsForCategoryTask(Category cat, TextView tvUnread, Context context) {
    mTvUnread = tvUnread;
    mCategory = cat;
    mContext = context;
}

@Override
protected JSONArray doInBackground(String... params) {
    mCategoryId = params[0];

     ...

}

@Override
protected void onProgressUpdate(Integer... values) {
    mTvUnread.setText(Integer.toString(values[0]));
}

@Override
protected void onPostExecute(JSONArray result) {
    if(result != null && mThrown == null)
    {
        publishProgress(mCategory.getUnreadNewsSet().size());
    }
}

}

Does anybody what could be the reason for this weird behaviour? I checked that the AsyncTask are properly called when launching them only once pro Category, but just don't update the layout. Why launching the several times pro Category works?

UPDATE: I've been testing and looks like the problem is with the getView() function. If I check if the variable has been initialized then only the first element of the ListView changes...with all the values of the other items in the ListView!!

So looks like the TextView is trying to set the value is always the first one (first element of the ListView).

Any idea???

Answer 1

Look at this:

Category cat = mCategoriesList.get(position);
tvCategory.setText(cat.getName());
if(!cat.isInitialized()) //<-- If I delete this line it works, but inefficienly, as the AsyncTask is launched many times repeatedly
{
    cat.setIsInitialized(true)
    new GetNewsForCategoryTask(cat, tvUnreadNews, mContext).execute(cat.getId());
}

I think that you have to call setIsInitialized(true) on mCategoriesList.get(position) , not on cat , because when getView() is called again, mCategoriesList.get(position) always returns uninitialized one, because you call setIsInitialized(true) on cat , not in mCategoriesList .