Android: ListView is not updated on notifyDataSetChanged ();

Question

I have a custom BaseAdapter and an add button in the main action. The button opens a dialog with a text box, and you can add new items to the list this way. The problem is that the list is not refreshing. In the onActivityResult () function, I print the number of elements in the list, and every time I click "OK" in the dialog box, the number increases, so I know that this is just an update that does not work. My base adapter and my activity:

class ListaOrase extends BaseAdapter{ private Activity context; ArrayList<String> orase; public ListaOrase(Activity context){ this.context=context; orase=new ArrayList<String>(); } public void add(String string){ orase.add(string); this.notifyDataSetChanged(); } public View getView (int position, View convertView, ViewGroup list) { View element; if (convertView == null) { LayoutInflater inflater = context.getLayoutInflater(); element = inflater.inflate(R.layout.lista, null); } else element = convertView; TextView elementLista=(TextView)element.findViewById(R.id.elementLista); elementLista.setText(orase.get(position)); return element; } } public class WeatherAppActivity extends ListActivity { Button buton; ListaOrase lista; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); lista=new ListaOrase(this); buton=(Button)findViewById(R.id.buton); lista.add("Bucuresti"); lista.add("Sibiu"); setListAdapter(lista); } public void add(View view){ Intent intent=new Intent(); intent.setClass(this, Adauga.class); startActivityForResult(intent, 0); } public void onActivityResult (int requestCode, int responseCode, Intent data){ System.out.println("Apelata"); if(responseCode==1){ lista.add(data.getStringExtra("oras")); // e chiar getText() System.out.println(lista.getCount()); lista.notifyDataSetChanged(); } } } 

As you can see, I am trying to update (notifyDataSetChanged ();) both when adding a new element (in the BaseAdapter extensible class) and in the onActivityResult method after the dialog passes the new element to the main action. I repeat, the IS element is added to the list, because the counter increases, it just does not update.

Thank you for your responses!

Answer 1

It’s normal that it does not update, you add an item to “lista”, but the adapter saves its own copy of this list, so either you set the list in the adapter again and then call notifyDataChanged or add a new adapter element.

Anyway, I see a couple of strange things, I could compile everything using an array adapter, you do not need to add add, etc. I wrote the code by simply adding yours:

 public class WeatherAppActivity extends ListActivity { Button buton; ItemsAdapter lista; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); List<String> initialList = new ArrayList<String>(); initialList.add("Bucuresti"); initialList.add("Sibiu"); lista=new ItemsAdapter(this, initialList); buton=(Button)findViewById(R.id.button1); buton.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { lista.add(""+System.currentTimeMillis()); // e chiar getText() lista.notifyDataSetChanged(); } }); setListAdapter(lista); } class ItemsAdapter extends ArrayAdapter<String> { public ItemsAdapter(Context context, List<String> list) { super(context, R.layout.lista, list); } @Override public View getView(final int position, View row, final ViewGroup parent) { final String item = getItem(position); ItemWrapper wrapper = null; if (row == null) { row = getLayoutInflater().inflate(R.layout.lista, parent, false); wrapper = new ItemWrapper(row); row.setTag(wrapper); } else { wrapper = (ItemWrapper) row.getTag(); } wrapper.refreshData(item); return row; } class ItemWrapper { TextView text; public ItemWrapper(View row) { text = (TextView) row.findViewById(R.id.elementLista); } public void refreshData(String item) { text.setText(item); } } } } 

This is the xml that I used:

main.xml

 <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" > <Button android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentBottom="true" android:layout_centerHorizontal="true" android:layout_marginBottom="63dp" android:text="Button" /> <ListView android:id="@id/android:list" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_alignParentTop="true" android:layout_centerHorizontal="true" > </ListView> </RelativeLayout> 

lista.xml

 <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <TextView android:id="@+id/elementLista" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Medium Text" android:textAppearance="?android:attr/textAppearanceMedium" /> </LinearLayout> 

This is the adapter version using the base adapter:

 class ItemsBaseAdapter extends BaseAdapter { private List<String> items; private Context mContext; public ItemsBaseAdapter(Context context, List<String> list) { items = list; mContext = context; } public void addItem(String str) { items.add(str); } @Override public View getView(final int position, View row, final ViewGroup parent) { final String item = (String) getItem(position); ItemWrapper wrapper = null; if (row == null) { row = getLayoutInflater().inflate(R.layout.lista, parent, false); wrapper = new ItemWrapper(row); row.setTag(wrapper); } else { wrapper = (ItemWrapper) row.getTag(); } wrapper.refreshData(item); return row; } class ItemWrapper { TextView text; public ItemWrapper(View row) { text = (TextView) row.findViewById(R.id.elementLista); } public void refreshData(String item) { text.setText(item); } } @Override public int getCount() { return items.size(); } @Override public Object getItem(int position) { return items.get(position); } @Override public long getItemId(int position) { // TODO Auto-generated method stub return 0; } } 

And this is the version of the list item, which also includes the image on the left:

 <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" > <ImageView android:layout_height="wrap_content" android:src="@android:drawable/btn_star_big_on" android:scaleType="fitCenter" android:layout_width="wrap_content" /> <TextView android:id="@+id/elementLista" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Medium Text" android:textAppearance="?android:attr/textAppearanceMedium" /> </LinearLayout>