CODEWITHSUNDEEP
androidandroid-listview
BurninatorDor
BurninatorDor

Reputation: 1117

Allow scrolling listview after setSelection

I have a listview which I am forcefully scrolling to the bottom of the list, whenever the list is updated. However, after scrolling to the bottom of the list, for some reason, the listview becomes fixated at that point and the user cannot scroll back and forth on the list to see the other data.

Question: After setSelection(list.getBottom()), what should I have in order to allow scrolling through the entire list once again?

    @Override
        public View getView(int position, View convertView, ViewGroup parent) {
        /* the list is being populated here - the code has been omitted */          

            list.populateFrom(date, name, class);
            list.clearFocus();
            list.post(new Runnable() {

                @Override
                public void run() {

                    list.setSelection(list.getBottom());
                }
            });


        return list;
    }
}

Upvotes: 1

Views: 2365

Answers (3)

user1707035
user1707035

Reputation:

As suggested by A--C, it is problem with the

list.setSelection(list.getBottom());

Every time your getView() is called you are moving/scrolling the view to the bottom, there fore when you are trying to scroll the view again then your getView() is called and again you again move to bottom. So instead of setting the selection in the listview to the bottom in the getView() you should do it in your activity/fragment. In activity you observe the change and set selection to the bottom.

If this was helpful explanation for your problem, do upvote

Upvotes: 0

Raghunandan
Raghunandan

Reputation: 133570

   cus= new Customlistadapter(paramets for customer adapter));//Custom list adapter
   lv1 = (ListView) findViewById(R.id.list);
   lv1.setTranscriptMode(AbsListView.TRANSCRIPT_MODE_ALWAYS_SCROLL);
   lv1.setStackFromBottom(true);
   cus.notifyDataSetChanged();// for refreshing listview with updates
   lv1.setAdapter(cus);
   cus.registerDataSetObserver(new DataSetObserver() {
   @Override
   public void onChanged() {
    super.onChanged();
    lv1.setSelection(cus.getCount() - 1);    
   }
 });

Use the above in your activity class. A--C has pointed to the problem.

If you are using AysncTask in your activity class try the below code.

  private class DownloadFilesTask extends AsyncTask<Void, Void, VOid> {
 protected void onPreExecute()
 {
     //display progress dialog
 }
 protected Long doInBackground(Void... params) {
   // get data from server
     return null;
 }


 protected void onPostExecute(Void params) {
  // dismiss dialog
  //set  data
  // paste the above listview code here. 
 }

}

Upvotes: 0

A--C
A--C

Reputation: 36449

The problem lies with the fact that you are calling 

 list.setSelection(list.getBottom());

in getView(), which is called every single time the ListView needs more Views drawn. This means you constantly scroll down.

Instead, update the data set you have from outside the Adapter class (such as from an Activity/Fragment), then either reset the ListView's adapter or clear the adapter and readd the items, then call setSelection().

One way to do this:

  • Activity starts an AsyncTask

  • AsyncTask updates a List of data via doInBackground().

  • In onPostExecute(), instantiate the Adapter with the List passed from doInBackground(). Or clear the data set of the Adapter you currently have, then loop through the List and re-add the items to the Adapter.

  • If reinstantiating the Adapter, set the ListView's Adapter to what you have created.

  • call ListView#setSelection()

Upvotes: 3

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