How do I get the cursor value of a ListView's item onItemClick?

Question

I've created a database with tables (categories) with columns (_id, title etc). I want to read these categories' data from my database and list them in a ListView.

Here is my code:

   public class MainActivity extends listActivity{

    private ArrayAdapter arrayAdapter;
    ArrayList results = new ArrayList();
    ListView catlist;
    Cursor cur;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        catlist = getListView();

        int parentid = getIntent().getIntExtra("catid", 0);
        openAndQueryDatabase(parentid);

        displayCatListView();

    }

    private void displayCatListView() {

        setListAdapter(new ArrayAdapter<String>(this,
                android.R.layout.simple_list_item_1, results));


        catlist.setOnItemClickListener(new OnItemClickListener() {

               @Override
               public void onItemClick(AdapterView<?> parent, View v,
                 final int position, long id) {


                Toast.makeText(MainActivity.this,
                  "List View Clicked:" + position, Toast.LENGTH_LONG)
                  .show();
               }
              });     

    }

    private void openAndQueryDatabase(int parentid) {
        DataBaseHelper db = new DataBaseHelper(this);

        SQLiteDatabase dbr = db.getReadableDatabase();
        cur = dbr.rawQuery(
                "SELECT _id, title, has_sub FROM categories where parent_id=?",
                new String[] { String.valueOf(parentid) });


        if (cur != null) {
            while (cur.moveToNext()) {

                int cat_id = cur.getInt(cur.getColumnIndex("_id"));
                String cattitle = cur.getString(cur.getColumnIndex("title"));
                int has_sub = cur.getInt(cur.getColumnIndex("has_sub"));
                results.add(cat_id + cattitle + has_sub);
            }
            cur.close();
        }

        db.close();

    }
}

1. I can get the item's position onItemClick, but I want to get their row's _id onItemClick. How do I do this?
2. I'm new to this. Are there any mistakes in my code?

Thanks a lot.

Solution 1

Instead of

int cat_id = cur.getInt(cur.getColumnIndex("_id"));
String cattitle = cur.getString(cur.getColumnIndex("title"));
int has_sub = cur.getInt(cur.getColumnIndex("has_sub"));
results.add(cat_id + cattitle + has_sub);

create a Category class to contain these values, and use a parameterized ArrayList. Something like

class Category {
    public int cat_id;
    public String cattitle;
    public int has_sub;

    public Category(int cat_id, ...) {
        // constructor logic here
    }
}

and

results.add(new Category(cat_id, cattitle, has_sub));

With this, you can set the onItemClickListener as such:

        catlist.setOnItemClickListener(new OnItemClickListener() {

           @Override
           public void onItemClick(AdapterView<?> parent, View v,
             final int position, long id) {
                 Category clickedCategory = results.get(position);
                 int id = clickedCategory.cat_id;

                 // do something with id
           }
          });     

Your ArrayList is the data source of your ArrayAdapter, and position corresponds to the index of the clicked Category in it.

Solution 2

Use CursorAdapter(http://developer.android.com/reference/android/widget/CursorAdapter.html) instead, when you are using ArrayAdapter it's exceed memory allocation, and also you wouldn't get notifications if db changed.

Moreover in case of using CursorAdapter you will have

public void onItemClick(AdapterView<?> parent, View v, final int position, long id)

the "id" param will concur with table's _id field

to get the whole row just do

adapter.getItem(int position)

Comments

[Admin]

thank you for your answer. could you explain this more this part please: class Category { public int cat_id; public String cattitle; public int has_sub; public Category(int cat_id, ...) { // constructor logic here } } or link a complete example?

[numediaweb]

@ErikR Could you please point to a full tutorial on using object instead of arraylist?

[ErikR]

@numediaweb My code above uses the original ArrayList in Ji.Mack's code to hold instances of the Category class. So we're using objects with an ArrayList, not instead of.