doInBackground not working in Android fragment

Question

I have a fragment Fragment1.In that fragment I am parsing XML and populating list view.I have to execute the function parsing and population of list view in background of fragment.So that it will not disturb user.When I used Asynctask and defined population of list view function inside doInBackground it show an error like "an error occurred while executing doinbackground() ". What am I done wrong here?

Here is my Fragment

Fragment1=>

public class Kerala extends Fragment{
   static String URL = "";
// XML node keys
static final String KEY_HEAD = "item"; // parent node
//static final String KEY_TITLE = "title";
static final String KEY_DATE = "pubDate";
public static String headflag="";
int f=0;
GridView list;
    KeralaAdapter adapter;


  public static String[] Title;
    public static String[] Description;
    public static String[] Tit;
    public static String[] Tit2;
    public static String[] Desc;
    public static String[] Desc2;

    public static String[] image;
    public static String[] Date;
    public static String[] Flash;
    public static String[] Fl;
    public static String[] Fl2;

private TextView mMessageView;
private Button mClearButton;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    // Inflating layout
    View v = inflater.inflate(R.layout.kerala_fragment, container, false);
    // We obtain layout references

    return v;

}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    new ProgressAsyncTask().execute();


}


 public void populate_listview()
 {


     URL="http://www.abcd.com/en/rssfeeds/9/latest/rss.xml";



    ArrayList<HashMap<String, String>> newsList = new ArrayList<HashMap<String, String>>();

    XMLParser parser = new XMLParser();
    String xml = parser.getXmlFromUrl(URL); // getting XML from URL
    Document doc = parser.getDomElement(xml); // getting DOM element

    NodeList nl = doc.getElementsByTagName(KEY_HEAD);
    // looping through all song nodes <song>
    NodeList itemLst = doc.getElementsByTagName("item");
    String MarqueeStr="";

    for (int i = 0; i < nl.getLength(); i++) {
        // creating new HashMap
        HashMap<String, String> map = new HashMap<String, String>();
        Element e = (Element) nl.item(i);

        //map.put(KEY_DATE, parser.getValue(e, KEY_DATE));

        newsList.add(map);


 }









    list=(GridView)getActivity().findViewById(R.id.grid2);

    // Getting adapter by passing xml data ArrayList
            adapter=new KeralaAdapter(getActivity(), newsList);        
            list.setAdapter(adapter);





}






 public void StartProgress(){
        new ProgressAsyncTask().execute();
    }

    public class ProgressAsyncTask extends 
        AsyncTask<Void, Integer, Void> {

        int myProgress;

        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
            super.onPreExecute();

            myProgress = 0;


        }

        @Override
        protected void onPostExecute(Void result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);



        }

        @Override
        protected Void doInBackground(Void... arg0) {
            // TODO Auto-generated method stub


                keralaparser.parse();//here I am calling both functions
            populate_listview();








            return null;
        }

        @Override
        protected void onProgressUpdate(Integer... values) {
            // TODO Auto-generated method stub





        }

        }
}

Here is my error log,

11-14 18:29:42.705: E/AndroidRuntime(10530): java.lang.RuntimeException: An error occured while executing doInBackground()
11-14 18:29:42.705: E/AndroidRuntime(10530):    at android.os.AsyncTask$3.done(AsyncTask.java:278)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at java.util.concurrent.FutureTask.run(FutureTask.java:137)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at java.lang.Thread.run(Thread.java:856)
11-14 18:29:42.705: E/AndroidRuntime(10530): Caused by: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
11-14 18:29:42.705: E/AndroidRuntime(10530):    at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:4056)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at android.view.ViewRootImpl.focusableViewAvailable(ViewRootImpl.java:2210)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at android.view.ViewGroup.focusableViewAvailable(ViewGroup.java:657)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at android.view.ViewGroup.focusableViewAvailable(ViewGroup.java:657)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at android.view.ViewGroup.focusableViewAvailable(ViewGroup.java:657)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at android.view.ViewGroup.focusableViewAvailable(ViewGroup.java:657)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at android.view.ViewGroup.focusableViewAvailable(ViewGroup.java:657)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at android.view.ViewGroup.focusableViewAvailable(ViewGroup.java:657)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at android.view.ViewGroup.focusableViewAvailable(ViewGroup.java:657)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at android.view.View.setFlags(View.java:6736)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at android.view.View.setFocusableInTouchMode(View.java:4714)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at android.widget.AdapterView.checkFocus(AdapterView.java:705)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at android.widget.GridView.setAdapter(GridView.java:186)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at com.madhyamam.malayalam2.Kerala.populate_listview(Kerala.java:149)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at com.madhyamam.malayalam2.Kerala$ProgressAsyncTask.doInBackground(Kerala.java:215)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at com.madhyamam.malayalam2.Kerala$ProgressAsyncTask.doInBackground(Kerala.java:1)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at android.os.AsyncTask$2.call(AsyncTask.java:264)
11-14 18:29:42.705: E/AndroidRuntime(10530):    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)

score 2 · Accepted Answer · answered Nov 14 '12 at 13:18

2

You are doing changes to the ui in your async thread. Move the last 3 lines where you asign a new adapter to the list from your populate_listview() methode to onPostExecute(). This Method is executed on your ui thread and can change your ui.

answered Nov 14 '12 at 13:18

Christian S.

321
1
4

score 1 · Answer 2 · answered Nov 14 '12 at 13:17

1

Call populate_listview(); in onPostExecute() of your Asynctask..

Log shows

Caused by: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.

UI cannot be updated across threads directly.

answered Nov 14 '12 at 13:17

Ron

24,175
8
56
97

Calling the `populate_listview()` method in `onPostExecute` would make the `AsyncTask` completely useless. – user Nov 14 '12 at 13:19
@Luksprog No. He does some parsing in doInBackground before calling `populate_listview()`.. – Ron Nov 14 '12 at 13:23

score 1 · Answer 3 · answered Nov 14 '12 at 15:01

The idea of using an AsyncTask is to do background processes with the exception that no element of your current UI will be accessed / modified during the background process. This is a different thread. If you are trying to update / edit a list (ex: ListView / custom LinearLayout implemented like list views) of your current activity / fragment / UI, then you may consider generating in the background process the list [may be Plain Old Java Objects (POJOs) or may be views - new instances / inflated] and returning it as a result of the doInBackground() method:

@Override
protected View doInBackground(Void... params) {
    return generateListResults();
}

After this, you may now access / modify your current activity / fragment / UI. This may be inside the onPostExecute() method, passing the result as a parameter, which may look like this, [following the doInBackground() method]:

@Override
protected void onPostExecute(View result) {
    resultContainer.addView(result);
    dialog.dismiss();
    super.onPostExecute(result);
}

You may opt to show a loading dialog before starting the background process:

@Override
protected void onPreExecute() {
    dialog = ProgressDialog.show(context, res.getString(R.string.searching), res.getString(R.string.wait), true);
    resultContainer.removeAllViews();
    super.onPreExecute();
}

doInBackground not working in Android fragment

3 Answers3

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