将自定义数据添加到ListView和ArrayAdapter项

Question

I'm creating an Android application. Inside a Fragment I have a ListView that is populated using an ArrayAdapter and an ArrayList . I'm using android.R.layout.simple_list_item_1 for the layout for the list items. I want to have an OnItemClickListener , so that when an item is clicked it will show another Activity based on its data.

The problem is, there may be items with the same name. I'd like to attach an ID value to each of the elements, so that my code can distinguish them from each other.

My items that I use to populate the list are of a custom class to hold their data, but the important fields here are the ID and the name (which is shown in the ListView ).

My code for populating the ListView :

List<String> items;
ArrayAdapter<String> adapter;
List<MyCustomDataObject> listOfDataObjects;

...

// Get the ListView
ListView list = (ListView) layoutRootView.findViewById(R.id.listView1);
// Create the item List and the ArrayAdapter for it
items = new ArrayList<String>();
adapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, items);
// Set the list adapter
list.setAdapter(adapter);
// Add the data items
for (MyCustomDataObject obj : listOfDataObjects) {
    items.add(obj.name);
}
items.add(getResources().getString(R.string.no_items));
// Create the item click listener
list.setOnItemClickListener(new OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        // Open the Activity based on the item
    }
});

How could I add an ID to the list items for identifying each item?

Answer 1

The solution is quite simple actually.

You're populating the ListView from a List . The List is an ordered collection of items, so when adding it as the datasource for the ListView you will always know the index of each item.

So when selecting an item from the ListView you get the position of the View clicked. This position will correspond to the position in your List .

You won't really need the id field of your MyCustomDataObject , but of course when you populate the List of MyCustomDataObject you could use a normal for-loop (not enhanced) and use the index to set the id of each MyCustomDataObject .

Answer 2

Lookup the position in listOfDataObjects to find the ID:

// Create the item click listener
list.setOnItemClickListener(new OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        if (position==listOfDataObjects.size()) {   .... no_items clicked ... }
        else {
          MyCustomDataObject obj = listOfDataObjects.get(position);
          ... // Open the Activity based on the item
        }
    }
});