how to update an Android ListActivity on changing data of the connected SimpleCursorAdapter
- by 4485670
I have the following code.
What I want to achieve is to update the shown list when I click an entry so I can traverse through the list.
I found the two uncommented ways to do it here on stackoverflow, but neither works.
I also got the advice to create a new ListActivity on the data update, but that sounds like wasting resources?
EDIT: I found the solution myself. All you need to do is call "SimpleCursorAdapter.changeCursor(new Cursor);". No notifying, no things in UI-Thread or whatever.
import android.app.ListActivity;
import android.database.Cursor;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
public class MyActivity extends ListActivity {
private DepartmentDbAdapter mDbHelper;
private Cursor cursor;
private String[] from = new String[] { DepartmentDbAdapter.KEY_NAME };
private int[] to = new int[] { R.id.text1 };
private SimpleCursorAdapter notes;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.departments_list);
mDbHelper = new DepartmentDbAdapter(this);
mDbHelper.open();
// Get all of the departments from the database and create the item list
cursor = mDbHelper.fetchSubItemByParentId(1);
this.startManagingCursor(cursor);
// Now create an array adapter and set it to display using our row
notes = new SimpleCursorAdapter(this, R.layout.department_row, cursor, from, to);
this.setListAdapter(notes);
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
// get new data and update the list
this.updateData(safeLongToInt(id));
}
/**
* update data for the list
*
* @param int departmentId id of the parent department
*/
private void updateData(int departmentId) {
// close the old one, get a new one
cursor.close();
cursor = mDbHelper.fetchSubItemByParentId(departmentId);
// change the cursor of the adapter to the new one
notes.changeCursor(cursor);
}
/**
* safely convert long to in to save memory
*
* @param long l the long variable
*
* @return integer
*/
public static int safeLongToInt(long l) {
if (l < Integer.MIN_VALUE || l > Integer.MAX_VALUE) {
throw new IllegalArgumentException
(l + " cannot be cast to int without changing its value.");
}
return (int) l;
}
}
