Question

i´m in trouble with a custom Listview and (Checkboxes or Button). I follow a guide (the android devolopers´s cookbook) and my custom Listview show correctly. An visisble Error occured when selected Checkboxes are scrolling.(Wrong Checkboexes are checked)

I followed the guide on
http://www.vogella.de/articles/AndroidListView/article.html#listviews_performance
but it doesn´t work. How to save the state correctly?

Greeting
Andreas

Answer 1

You will have to save the checked items in a list variable (in your Adapter subclass) and set the correct state (checked/unchecked) depending upon whether the item is present in the list variable.

private List<MyItem> mCheckedItems; //In your adapter subclass

Add/remove an item from the list variable:

//The AdapterView.OnItemClickListener, is present where you set myListView.setOnItemClickListener(this);
public void onItemClick(AdapterView<?> adapterView, View view, int position, long id)
{

    MyItem item = myAdapter.getItem(position);
    myAdapter.updateCheckedItems(item);
}

public void updateCheckedItems(MyItem item) //In your adapter subclass
{
        if(!mCheckedItems.contains(item))
        {
            mCheckedItems.add(item);
        }
        else
        {
            mCheckedItems.remove(item);
        }
}

Set the correct state of the checkbox:

public View getView(int position , View view , ViewGroup parent) //In your adapter subclass
{
     final MyItem item = getItem(position);
     CheckBox checkBox = (CheckBox)view.findViewById(R.id.checkBox);
     checkBox.setChecked(mCheckedItems.contains(item));
}