Weird behavior of ListView

Question

I have weird problem with ListView on android 2.3. Application is simple todo list with EditText and ListView. Each time you write text and press ENTER text is added to ListView. Problem happend when I add 3rd element, order in ListView mess up (3rd element become 1st). I solve this problem so I rebind data every time in getView but on that way I lose ViewHolder pattern optimization. On 4.0 I don't have problem with same code :). Does anyone know what is reason for this behaviour?

This is my getView method.

public View getView(int position, View convertView, ViewGroup parent) {

    final ViewHolder view;
    if(convertView == null) {

        convertView = ((LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.todo_single_row, parent, false);

        view = new ViewHolder();
        view.text = (TextView)convertView.findViewById(R.id.tvToDoText);
        view.date = (TextView)convertView.findViewById(R.id.tvToDoDate);

        convertView.setTag(view);
    }
    else
    {
        view = (ViewHolder)convertView.getTag();
    }

    view.text.setText(ToDoList.getInstance().getToDoList().get(position).getText());
    view.date.setText(ToDoList.getInstance().getToDoList().get(position).getDate().toString());

    return convertView;
}

I try also to sort my adapter but did not help :(.

Comparator<Item> comparator = new Comparator<Item>() {
         public int compare(final Item item1, final Item item2) {
                return item1.getText().compareToIgnoreCase(item2.getText());
              };
    };

public class Item {
private String text;
private Date date;

public Item(String text) {

    this.text = text;
    this.date = new Date(java.lang.System.currentTimeMillis());
}

public String getText() {
    return text;
}

public void setText(String text) {
    this.text = text;
}

public Date getDate() {
    return date;
}

public void setDate(Date date) {
    this.date = date;
}

}

score 1 · Answer 1 · answered Feb 14 '14 at 21:07

1

On 2.3 and earlier versions of Android list view elements are indexed by what is visible. You need to use listView.getFirstVisible() to get a specific element.

answered Feb 14 '14 at 21:07

Ben

1,285
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score 1 · Accepted Answer · answered Feb 14 '14 at 21:09

1

This actually happens because usually getView() processes rows in an order that Android determines. Many people think this is called sequentially and it's not, it's called within an order that establishes the Adapter.

You can, however, override this behavior. In that case, you could simply declare a Comparator. For instance, if the content of your rows are strings, this would be one way:

Comparator alphabeticalOrder = new Comparator<String>() {
  public int compare(final String str1, final String str2) {
    return str1.compareToIgnoreCase(str2);
  };
};

Afterwards, you simply set it on your Adapter.

adapter.sort(alphabeticalOrder);

answered Feb 14 '14 at 21:09

nKn

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Sorting will basically add an upper layout to the rendering operation of your rows. It will know it has to render, but also counts on that you've defined a `.sort()` method and this will survive, so your `ListView` will be sorted. – nKn Feb 14 '14 at 22:15
Yep, you have to call `.sort()` each time you add something. I use this, for example: `elemlist.add(nick2ban);` `adapter.sort(alphabet);` `adapter.notifyDataSetChanged();` – nKn Feb 14 '14 at 22:34
Please update your question and add your `Comparator`, and in case you're using a compound class, include it also. – nKn Feb 14 '14 at 22:49
Ok, after seeing your update, replace `return item1.getText().compareToIgnoreCase(item2.getText());` by `return item1.text.getText().compareToIgnoreCase(item2.text.getText());` I know they are private, use a `getMyText()` method or something like that or set them `public`, but currently you're getting the `String` representation of your Item, not the text inside! – nKn Feb 14 '14 at 23:10
Should indeed, and does? – nKn Feb 14 '14 at 23:28

Weird behavior of ListView

2 Answers2