how to use an ArrayAdapter in android of custom objects

Question

How can I use the properties of a custom object in a Listview. If I implement an ArrayAdapter with a list of Strings it displays fine in Listview but when I use a list of custom objects, it just outputs the memory address.

The code I have up to now:

ArrayList<CustomObject> allObjects = new ArrayList<>();

allObjects.add("title", "http://url.com"));


  ArrayAdapter<NewsObject> adapter = new ArrayAdapter<NewsObject>(this,
                android.R.layout.simple_list_item_1, android.R.id.text1, allNews);


        // Assign adapter to ListView
        listView.setAdapter(adapter);


        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

                Uri uri = Uri.parse( "http://www.google.com" );
                startActivity(new Intent(Intent.ACTION_VIEW, uri));
            }
        });

There is a similar question here but that is not what I need since I just need to have the title show in list view and when they click extract the url.

Answer 1

An ArrayAdapter displays the value returned by the toString() method, so you will need to override this method in your custom Object class to return the desired String. You will also need to have at least a getter method for the URL, so you can retrieve that in the click event.

public class NewsObject {
    private String title;
    private String url;

    public NewsObject(String title, String url) {
        this.title = title;
        this.url = url;
    }

    public String getUrl() {
        return url;
    }

    @Override
    public String toString() {
        return title;
    }
    ...
}

In the onItemClick() method, position will be the index in the ArrayList of your custom Objects corresponding to the list item clicked. Retrieve the URL, parse it, and call startActivity().

listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            NewsObject item = allNews.get(position);
            String url = item.getUrl();
            Uri uri = Uri.parse(url);
            startActivity(new Intent(Intent.ACTION_VIEW, uri));
        }
    });

Please note, I assumed your custom class is NewsObject, as that is what's used with your Adapter example.