在对话框中为列表视图设置适配器时发生NullpointerException

Question

I want to display a custom dialog that have a listview inside it. First take a look on my code below.

Dialog:

protected void onPostExecute(String file_url) {
        btnInvite.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {

                LayoutInflater inflater = getActivity().getLayoutInflater();

                Dialog dialog = new Dialog(getActivity());                                      
                AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());

                ListView lv = (ListView) dialog.findViewById(R.id.lvAddDialog); 
                ListviewContactAdapter adapter = new ListviewContactAdapter(getActivity(), listContact);
                lv.setAdapter(adapter);             

                builder.setView(inflater.inflate(R.layout.dialog_add, null))
                .setTitle("Invite people")                  
                .setNegativeButton("Cancel", new OnClickListener() {

                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        // TODO Auto-generated method stub
                        dialog.cancel();
                    }
                });                                 
                dialog = builder.create();
                dialog.show();                  
                }
        });
     }
}

Adapter:

public class ListviewContactAdapter extends BaseAdapter{

private static ArrayList<ListviewContactItem> listContact;

private LayoutInflater mInflater;

public ListviewContactAdapter(Context photosFragment, ArrayList<ListviewContactItem> results){
    listContact = results;
    mInflater = LayoutInflater.from(photosFragment);
}

@Override
public int getCount() {
    // TODO Auto-generated method stub
    return listContact.size();
}

@Override
public Object getItem(int arg0) {
    // TODO Auto-generated method stub
    return listContact.get(arg0);
}

@Override
public long getItemId(int arg0) {
    // TODO Auto-generated method stub
    return arg0;
}


public View getView(int position, View convertView, ViewGroup parent) {
    // TODO Auto-generated method stub
    ViewHolder holder;
    if(convertView == null){
        convertView = mInflater.inflate(R.layout.contact_item, null);
        holder = new ViewHolder();
        holder.txtname = (TextView) convertView.findViewById(R.id.lv_contact_item_name);          
        holder.txtphone = (TextView) convertView.findViewById(R.id.lv_contact_item_phone);

        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }

    holder.txtname.setText(listContact.get(position).GetName());
    holder.txtphone.setText(listContact.get(position).GetPhone());

    return convertView;
}

static class ViewHolder{
    TextView txtname, txtphone;
}
}

When I run the app show up an error that NullpointerException at:

ListviewContactAdapter adapter = new ListviewContactAdapter(getActivity(), listContact);

I googled it but still can't find where wrong. Looking for help.

Answer 1

Change this:

ListviewContactAdapter adapter = new ListviewContactAdapter(getActivity(), listContact);

to this:

ListviewContactAdapter adapter = new ListviewContactAdapter(YourCLassName.this, listContact);

OR, may be you didn't initialize listContact

Answer 2

Inflate your view and use the object returned by the inflater to look for the ListView inside the layout

View view = inflater.inflate(R.layout.dialog_add, null)
ListView lv = (ListView) view.findViewById(R.id.lvAddDialog); 
ListviewContactAdapter adapter = new ListviewContactAdapter(getActivity(), listContact);
lv.setAdapter(adapter);             
builder.setView(view);

Answer 3

When you get the ListView yet not set te layout in the Dialog. You need build first your dialog and after get the ListView

Check this:

protected void onPostExecute(String file_url) {
    btnInvite.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {

            LayoutInflater inflater = getActivity().getLayoutInflater();

            AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());


            builder.setView(inflater.inflate(R.layout.dialog_add, null))
            .setTitle("Invite people")                  
            .setNegativeButton("Cancel", new OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {
                    // TODO Auto-generated method stub
                    dialog.cancel();
                }
            });                                 
            Dialog dialog = builder.create();

            ListView lv = (ListView) dialog.findViewById(R.id.lvAddDialog); 
            ListviewContactAdapter adapter = new ListviewContactAdapter(getActivity(), listContact);
            lv.setAdapter(adapter);     
            dialog.show();                  
            }
    });
 }

}