How to refresh Android listview?

Question

How to refresh an Android ListView after adding/deleting dynamic data?

Answer 1

If you are using SimpleCursorAdapter try calling requery() on the Cursor object.

Answer 2

I was the same when, in a fragment, I wanted to populate a ListView (in a single TextView) with the mac address of BLE devices scanned over some time.

What I did was this:

public class Fragment01 extends android.support.v4.app.Fragment implements ...
{
    private ListView                listView;
    private ArrayAdapter<String>    arrayAdapter_string;

...

@Override
public void onActivityCreated(Bundle savedInstanceState)
{
    ...
    this.listView= (ListView) super.getActivity().findViewById(R.id.fragment01_listView);
    ...
    this.arrayAdapter_string= new ArrayAdapter<String>(super.getActivity(), R.layout.dispositivo_ble_item, R.id.fragment01_item_textView_titulo);
    this.listView.setAdapter(this.arrayAdapter_string);
}


@Override
public void onLeScan(BluetoothDevice device, int rssi, byte[] scanRecord)
{
    ...
    super.getActivity().runOnUiThread(new RefreshListView(device));
}


private class RefreshListView implements Runnable
{
    private BluetoothDevice bluetoothDevice;

    public RefreshListView(BluetoothDevice bluetoothDevice)
    {
        this.bluetoothDevice= bluetoothDevice;
    }

    @Override
    public void run()
    {
        Fragment01.this.arrayAdapter_string.add(new String(bluetoothDevice.toString()));
        Fragment01.this.arrayAdapter_string.notifyDataSetChanged();
    }
}

Then the ListView began to dynamically populate with the mac address of the devices found.

Answer 3

If you want to update the UI listview from a service, then make the adapter static in your Main activity and do this:

@Override
public void onDestroy() {
    if (MainActivity.isInFront == true) {
        if (MainActivity.adapter != null) {
            MainActivity.adapter.notifyDataSetChanged();
        }

        MainActivity.listView.setAdapter(MainActivity.adapter);
    }
}    

Answer 4

If I talked about my scenario here, non of above answers will not worked because I had activity that show list of db values along with a delete button and when a delete button is pressed, I wanted to delete that item from the list.

The cool thing was, I did not used recycler view but a simple list view and that list view initialized in the adapter class. So, calling the notifyDataSetChanged() will not do anything inside the adapter class and even in the activity class where adapter object is initialized because delete method was in the adapter class.

So, the solution was to remove the object from the adapter in the adapter class getView method(to only delete that specific object but if you want to delete all, call clear()).

To you to get some idea, what was my code look like,

public class WordAdapter extends ArrayAdapter<Word> {
  Context context;

  public WordAdapter(Activity context, ArrayList<Word> words) {}
    //.......

    @NonNull
    @Override
    public View getView(final int position, View convertView, ViewGroup group) {
      //.......
     ImageButton deleteBt = listItemView.findViewById(R.id.word_delete_bt);
     deleteBt.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
             if (vocabDb.deleteWord(currentWord.id)) {
                //.....
             } else{
                //.....
             }
             remove(getItem(position)); // <---- here is the trick ---<
             //clear() // if you want to clear everything
         }
    });
 //....

Note: here remove() and getItem() methods are inherit from the Adapter class.

• remove() - to remove the specific item that is clicked
• getItem(position) - is to get the item(here, thats my Word object that I have added to the list) from the clicked position.

This is how I set the adapter to the listview in the activity class,

    ArrayList<Word> wordList = new ArrayList();
    WordAdapter adapter = new WordAdapter(this, wordList);

    ListView list_view = (ListView) findViewById(R.id.activity_view_words);
    list_view.setAdapter(adapter);

Answer 5

I think it depends on what you mean by refresh. Do you mean that the GUI display should be refreshed, or do you mean that the child views should be refreshed such that you can programatically call getChildAt(int) and get the view corresponding to what is in the Adapter.

If you want the GUI display refreshed, then call notifyDataSetChanged() on the adapter. The GUI will be refreshed when next redrawn.

If you want to be able to call getChildAt(int) and get a view that reflects what is what is in the adapter, then call to layoutChildren(). This will cause the child view to be reconstructed from the adapter data.

Answer 6

Also you can use this:

myListView.invalidateViews();