在adapter.notifyDataSetChanged（）之后，Listview不会更新

Question

I have this onCreateView in a fragment. It contains a listview that is being fed by ListViewAdapterNahrung . My problem is that this listview does not update after adapter.notifyDataSetChanged(); .

public class NahrungFragment extends Fragment {
    private ArrayList<HashMap<String, String>> list;
    HashMap<String,String> temp;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_nahrung, container, false);

        list=new ArrayList<HashMap<String,String>>();
        temp=new HashMap<String, String>();
        temp.put("Bezeichnung", "Bezeichnung");
        list.add(temp);

        final ListViewAdapterNahrung adapter=new ListViewAdapterNahrung(getActivity(), list);
        listView.setAdapter(adapter);

        etBez.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {

            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {

                list=new ArrayList<HashMap<String,String>>();
                Cursor c=mydatabase.rawQuery("SELECT * FROM nahrung WHERE [bezeichnung] LIKE '%"+etBez.getText().toString()+"%' ", null);
                if(c.getCount()>0)
                {
                    while(c.moveToNext())
                    {
                        temp=new HashMap<String, String>();
                        temp.put("Bezeichnung", c.getString(0));
                        list.add(temp);
                    }
                    adapter.notifyDataSetChanged();
                }
            }

            @Override
            public void afterTextChanged(Editable s) {

            }
        });

        return v;
    }
}

This is ListViewAdapterNahrung :

public class ListViewAdapterNahrung extends BaseAdapter {

    public ArrayList<HashMap<String, String>> list;
    Activity activity;
    TextView tvBezeichnung;
    private static final String FIRST_COLUMN="Bezeichnung";
    public ListViewAdapterNahrung(Activity activity, ArrayList<HashMap<String, String>> list){
        super();
        this.activity=activity;
        this.list=list;
    }

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

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

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return 0;
    }



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

        LayoutInflater inflater=activity.getLayoutInflater();
        if(convertView == null){
            convertView=inflater.inflate(R.layout.listview_nahrung, null);
            tvBezeichnung=(TextView) convertView.findViewById(R.id.tvName);
        }

        HashMap<String, String> map=list.get(position);
        tvBezeichnung.setText(map.get("Bezeichnung"));
        return convertView;
    }

}

Answer 1

Use list.clear() instead of reassignment to remove data

However, you should ideally use a CursorAdapter with a Database

Answer 2

You are not passing the data to your adapter, that's why you do not see the data updated. You have to pass the data to your adapter before call adapter.notifyDataSetChanged();

Try this:

...
@Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {

            list=new ArrayList<HashMap<String,String>>();
            Cursor c=mydatabase.rawQuery("SELECT * FROM nahrung WHERE [bezeichnung] LIKE '%"+etBez.getText().toString()+"%' ", null);
            if(c.getCount()>0)
            {
                while(c.moveToNext())
                {
                    temp=new HashMap<String, String>();
                    temp.put("Bezeichnung", c.getString(0));
                    list.add(temp);
                }
                adapter.updateData(list);
                adapter.notifyDataSetChanged();
            }
        }
,,,,

And in your adapter:

...
public void updateData(ArrayList<HashMap<String,String>> data){
    this.list.addAll(data);
}
...

Or if you want to set all new data :

...
public void updateData(ArrayList<HashMap<String,String>> data){
    this.list.clear();
    this.list.addAll(data);
}
...