android notifyDataSetChanged无法正常工作

Question

I bind an adapter to ListView in onCreate(), every time when activity is in onResume(), I will update the appinfos data in the adapter, and called notifyDataSetChanged in adapter setdata() method. But I don't get The ListView refreshed even the data changed in my adapter. I can't figure out what's the problem, could you help me out? thanks

Here is my activity using adapter and set data to listview.

List<AppInfo> appinfos = new ArrayList<AppInfo>();
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    getAppInfos();
    adapter=new UnistallListAdapter(this,appinfos);
    applistView.setAdapter(adapter);
}

@Override
protected void onResume() {
    getAppInfos();
    adapter.setdata(appinfos);
    super.onResume();
}


private List<AppInfo> getAppInfos() {
    appinfos.clear();
            //do some thing, new an item; and add into appinfos object
            //the appinfos data often changed here, 
            // as I uninstall app before activity called onResume().
           ......       
          appinfos.add(info);
            .....
    return appinfos;
}

Below is the main code of my UnistallListAdapter, and how to change its data.

private List<AppInfo>infos;
    public UnistallListAdapter(Context c,List<AppInfo>info)
{
    mContext = c;
    inflate=LayoutInflater.from(c);
    infos=info;
}

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

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

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

@Override
public View getView(final int position, View convertView, ViewGroup parent) {
    // TODO Auto-generated method stub

    ViewHold holder = null;
    if(convertView==null)
    {
        convertView=inflate.inflate(R.layout.uninstall_item, null);
        holder=new ViewHold();
        holder.name=(TextView)convertView.findViewById(R.id.name);
        holder.icon=(ImageView)convertView.findViewById(R.id.icon);

        holder.ai = infos.get(position);;
        convertView.setTag(holder);
    }
    else
    {
        holder=(ViewHold)convertView.getTag();
    }

    AppInfo ai = holder.ai;
    holder.name.setText(ai.mAppLabel);
    holder.icon.setImageDrawable(ai.mIcon);

    return convertView;
}

private class ViewHold
{
    AppInfo ai;
    ImageView icon;
    TextView name;
}
public void setdata(List<AppInfo> dataList) {
    infos = dataList;
    notifyDataSetChanged();
}

please give me some help, and any hint about reason is welcome. I would be highly appreciate your help.

Answer 1

Change this:

public void setdata(List<AppInfo> dataList) {
  infos = dataList;
  notifyDataSetChanged();
}

to

public void setdata(List<AppInfo> dataList) {
  infos.clear();
  infos.putAll(dataList);
  notifyDataSetChanged();
}

reset the data contained in the list NOT its reference.

Answer 2

holder.ai = infos.get(position);

You're storing an object reference in the view holder and never update that.

View holder is not supposed to contain references to data objects, just the views. Use getItem(position) to get an up-to-date data object each time in getView() .

Answer 3

In the onResume method you are making a call to getAppInfos();. However you are not assigning it your ArrayList appinfos. Hence it is not getting updated and passing the same list to setdata() method.

Do,

this.appinfos = getAppInfos();
adapter.setdata(appinfos);
super.onResume();

OR

adapter.setdata(getAppInfos());
super.onResume();

Answer 4

add applistView.setAdapter(adapter); in the onResume after adapter.setdata(appinfos);