Android ListView not refreshing after notifyDataSetChanged with data as Map

Question

I used list adapter with map values as data. When I use adapter.notifyDataSetChanged(); the data in the list not updating. But if I replace the Map with ArrayList everything working fine. Following is my adapter code.

public class CategoryAdapter extends BaseAdapter {
ArrayList<Category> list = new ArrayList<Category>();
Context context;

public CategoryAdapter(Context context, Map<String, Category> categories) {
    this.context = context;
    list.clear();
    list.addAll(categories.values());
}

@Override
    public int getCount() {
        return list.size();
    }

@Override
    public View getView(int position, View convertView, ViewGroup parent) {
        final ViewHandler handler;

        LayoutInflater inflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        if (convertView == null) {
            convertView = inflater.inflate(R.layout.category_list_item, null);
            handler = new ViewHandler();
            handler.name = (TextView) convertView.findViewById(R.id.name);
            handler.count = (TextView) convertView.findViewById(R.id.count);
            convertView.setTag(handler);
        } else {
            handler = (ViewHandler) convertView.getTag();
        }
        Category category = list.get(position);
        handler.name.setText(category.getMenuName());
        handler.count.setText(category.getCount() + "");
        if (category.getCount() <= 0) {
            handler.count.setVisibility(View.INVISIBLE);
        } else {
            handler.count.setVisibility(View.VISIBLE);
        }

        return convertView;
    }
}

and my activity code is

private void loadCategories() {
    sampleDB = openOrCreateDatabase(AppConstants.DB_NAME, MODE_PRIVATE,
            null);
    Cursor menuCursor = sampleDB.rawQuery("select * from menu", null);

    categories.clear();
    while (menuCursor.moveToNext()) {
        String menu = menuCursor.getString(menuCursor
                .getColumnIndex("name"));
        String id = menuCursor.getString(menuCursor.getColumnIndex("id"));
        Category category = new Category(menu, id);
        categories.put(id, category);
    }
    menuCursor.close();
    categoryAdapter.notifyDataSetChanged();
}

in oncreate() method I have declared adapter as follows

categoryAdapter = new CategoryAdapter(context, categories);
        categoryList.setAdapter(categoryAdapter);
        loadCategories();

Every time I click on refresh button it calls loadCategories(); method. In the same code if I replace Map with ArrayList everything working fine.

Now My question is why List is not refreshing with Map values. Please give me clarification regarding this.

Thanks in advance.

Where are you adding/changing the contents of the `categoryAdapter` — 0xDEADC0DE, Jun 27 '14 at 14:09
Sorry. `categoryAdapter` is declared using `categories` Map. See my updated Question. Everytime I click on refresh button loadCategories() will called. and with in that categories values changes. — Krish4906, Jun 27 '14 at 14:14
is `onCreate()` the only place where you create an instance of `CategoryAdapter`?. If so, the `ArrayList list` of your `categoryAdapter` doesn't not get updated — 0xDEADC0DE, Jun 27 '14 at 14:18
yes, `oncreate()` is the only place for creating inastance for `CategoryAdapter`. `ArrayList list` doesn't gets effected even if I use `notifyDataSetChanged()`. — Krish4906, Jun 27 '14 at 14:24
That is because you don't update the list of the adapter instance. Let me work out an answer which I think work. A little moment please... — 0xDEADC0DE, Jun 27 '14 at 14:27

score 5 · Accepted Answer · answered Jun 27 '14 at 14:33

You must add a method to your CategoryAdapter to change the instance's list, like so

public class CategoryAdapter extends BaseAdapter {
ArrayList<Category> list = new ArrayList<Category>();
Context context;

public CategoryAdapter(Context context, Map<String, Category> categories) {
    this.context = context;
    list.clear();
    list.addAll(categories.values());
}

@Override
public int getCount() {
    return list.size();
}

//ADD THIS METHOD TO CHANGE YOUR LIST
public void addItems(Map<String, Category> categories){
    list.clear();
    list.addAll(categories.values());
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    final ViewHandler handler;

    LayoutInflater inflater = (LayoutInflater) context
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    if (convertView == null) {
        convertView = inflater.inflate(R.layout.category_list_item, null);
        handler = new ViewHandler();
        handler.name = (TextView) convertView.findViewById(R.id.name);
        handler.count = (TextView) convertView.findViewById(R.id.count);
        convertView.setTag(handler);
    } else {
        handler = (ViewHandler) convertView.getTag();
    }
    Category category = list.get(position);
    handler.name.setText(category.getMenuName());
    handler.count.setText(category.getCount() + "");
    if (category.getCount() <= 0) {
        handler.count.setVisibility(View.INVISIBLE);
    } else {
        handler.count.setVisibility(View.VISIBLE);
    }

    return convertView;
}
}

and change your loadCategories like so (note that I call the addItems() before notifyDataSetChanged()

private void loadCategories() {
sampleDB = openOrCreateDatabase(AppConstants.DB_NAME, MODE_PRIVATE,
        null);
Cursor menuCursor = sampleDB.rawQuery("select * from menu", null);

categories.clear();
while (menuCursor.moveToNext()) {
    String menu = menuCursor.getString(menuCursor
            .getColumnIndex("name"));
    String id = menuCursor.getString(menuCursor.getColumnIndex("id"));
    Category category = new Category(menu, id);
    categories.put(id, category);
}
menuCursor.close();

//ADD CALL TO addItems TO UPDATE THE LIST OF THE categoryAdapter instance
categoryAdapter.addItems(categories);
categoryAdapter.notifyDataSetChanged();
}

without using `addItems()` if I repalce constructor with `public CategoryAdapter(Context context, ArrayList categories) { this.context = context; list=categories; }` it is working fine, but not with Map. Can you please explain me. — Krish4906, Jun 27 '14 at 14:48
no. after updating of categories ArrayList, I have called notifyDataSetChanged() and it is working fine. — Krish4906, Jun 30 '14 at 06:51
Oh I see now. In your constructor, you assign `categories` to `list`. So if you update your `categories`, you update your `list` and then your data has changed — 0xDEADC0DE, Jun 30 '14 at 08:08

score 2 · Answer 2 · answered Jun 27 '14 at 14:13

2

have you tried saying:

categoryList.setAdapter(null);
categoryList.setAdapter(categoryAdapter);

answered Jun 27 '14 at 14:13

erik

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Android ListView not refreshing after notifyDataSetChanged with data as Map

2 Answers2

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