Trying to access SQLite Database from within OnItemLongClickListener

Question

I am trying to delete an item that is stored in a SQLite DB and is being displayed in a listview.

The action that is giving me trouble is in the OnItemLongClickListener(). The error

The constructor DatabaseHandler(new AdapterView.OnItemLongClickListener(){}) is undefined

is with the instantiation of this line DatabaseHandler db = new DatabaseHandler(this);

I believe the problem is with the constructor of the DatabaseHandler, how can I use it from within onItemLongClickListener()?

MainActivity

public class MainActivity extends FragmentActivity implements OnClickListener {

ListView listView;
int lastIndex = -1;
ArrayList<Event> lstEvents = new ArrayList<Event>();

// detail view
TextView tvTitle, tvTime, tvDate;
ImageView ivPic;
View vw_master;

boolean _isBack = true;

ImageButton add;

String title;
String date;
String time;
int resId;

static final int PICK_CONTACT_REQUEST = 0;

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

    // // get detail controls
    tvTitle = (TextView) findViewById(R.id.textViewTitle);
    tvDate = (TextView) findViewById(R.id.textViewDate);
    tvTime = (TextView) findViewById(R.id.textViewTime);
    ivPic = (ImageView) findViewById(R.id.imageView1);

    add = (ImageButton) findViewById(R.id.add);
    add.setOnClickListener(this);

    // ///////////////////////////////LISTVIEW////////////////////////////////////////
    // Create the adapter to convert the array to views
    EventAdapter adapter = new EventAdapter(this, lstEvents);

    // attach adapter to a list view
    listView = (ListView) findViewById(R.id.listViewFragment);
    listView.setAdapter(adapter);



    listView.setOnItemLongClickListener(new OnItemLongClickListener() {

        @Override
        public boolean onItemLongClick(AdapterView<?> arg0, View arg1,
                int arg2, long arg3) {

            // TODO Auto-generated method stub
            DatabaseHandler db = new DatabaseHandler(this);
            Event event = db.getEvent(arg2);
            List<Event> events = db.deleteEvent(event);

            return false;
        }

    });
    // ///////////////////////////////LISTVIEW////////////////////////////////////////

    // /////////////////////////////DATABASE/////////////////////////////////////////////
    DatabaseHandler db = new DatabaseHandler(this);
    // /////////////////////////////DATABASE/////////////////////////////////////////////

    List<Event> events = db.getAllContacts();

    adapter.addAll(events);
    adapter.notifyDataSetChanged();

}

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    switch (v.getId()) {
    case R.id.add:
        Intent intent = new Intent(this, CreateActivity.class);
        startActivityForResult(intent, 100);
        break;
    }
}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    // /////////////////////////////DATABASE/////////////////////////////////////////////
    DatabaseHandler db = new DatabaseHandler(this);
    // /////////////////////////////DATABASE/////////////////////////////////////////////

    // Create the adapter to convert the array to views
    EventAdapter adapter = new EventAdapter(this, lstEvents);

    // attach adapter to a list view
    listView = (ListView) findViewById(R.id.listViewFragment);
    listView.setAdapter(adapter);

    if (requestCode == 100) {
        if (resultCode == RESULT_OK) {
            Bundle b = data.getExtras();
            title = b.getString("TITLE");
            time = b.getString("TIME");
            date = b.getString("DATE");

            Bitmap bitmap = b.getParcelable("BITMAP");


            /////CONVERTING A BITMAP TO A BYTE[]
            byte[] image = null;
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            bitmap.compress(Bitmap.CompressFormat.PNG, 100, bos);
            image = bos.toByteArray();
            /////////




            // /////////////////////////////DATABASE/////////////////////////////////////////////
            /**
             * CRUD OPERATIONS
             */

            Log.e("Insert: ", "Inserting ..");
            db.addEvent(new Event(0, title, time, date, image));

            // Reading all contacts
            Log.e("Reading: ", "Reading all contacts..");
            // List<Event> events = db.getAllContacts();
            List<Event> events = db.getAllContacts();
            adapter.addAll(events);
            adapter.notifyDataSetChanged();

            // logging all events

            for (Event ev : events) {
                String log = "Id: " + ev.get_Id() + " ,Title: "
                        + ev.get_title() + " ,Date: " + ev.get_date()
                        + " ,RESOURCEID: " + ev.get_image();
                // Writing Contacts to log
                Log.e("Name: ", log);

            }

            // /////////////////////////////DATABASE/////////////////////////////////////////////
        }

    }
}
}

DatabaseHandler

public class DatabaseHandler extends SQLiteOpenHelper {

// All Static variables
// Database Version
private static final int DATABASE_VERSION = 1;

// Database Name
private static final String DATABASE_NAME = "scheduleManager";

// Contacts table name
private static final String TABLE_EVENTS = "events";


// Contacts Table Columns names
private static final String KEY_ID = "id";
private static final String KEY_TITLE = "title";
private static final String KEY_TIME = "time";
private static final String KEY_DATE = "date";
private static final String KEY_IMAGE = "image";

public DatabaseHandler(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub
    String CREATE_EVENTS_TABLE = "CREATE TABLE " + TABLE_EVENTS + "("
            + KEY_ID + " INTEGER," + KEY_TITLE + " TEXT,"
            + KEY_TIME + " TEXT," + KEY_DATE + " TEXT," + KEY_IMAGE + " BLOB" + ")";
    db.execSQL(CREATE_EVENTS_TABLE);

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // Drop older table if existed
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_EVENTS);

    // Create tables again
    onCreate(db);

}

/**
 * All CRUD(Create, Read, Update, Delete) Operations
 */


//adding an event (NEEDS TO ADD DRAWABLE)
 public void addEvent(Event event) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(KEY_ID, event.get_Id()); //Event ID
        values.put(KEY_TITLE, event.get_title()); // Event Title
        values.put(KEY_TIME, event.get_time()); // Event Time
        values.put(KEY_DATE, event.get_date()); // Event Date
        values.put(KEY_IMAGE, event.get_image()); // Event RESOURCEID

        // Inserting Row
        db.insert(TABLE_EVENTS, null, values);
        db.close(); // Closing database connection
    }

   // Getting single contact
   public Event getEvent(int id) {
       SQLiteDatabase db = this.getReadableDatabase();

       Cursor cursor = db.query(TABLE_EVENTS, new String[] { KEY_ID,
               KEY_TITLE, KEY_TIME, KEY_DATE, KEY_IMAGE }, KEY_ID + "=?",
               new String[] { String.valueOf(id) }, null, null, null, null);
       if (cursor != null)
           cursor.moveToFirst();

       Event event = new Event(Integer.parseInt(cursor.getString(0)),
               cursor.getString(1), cursor.getString(2), cursor.getString(3), cursor.getBlob(4));
       // return contact
       return event;
   }


    // Getting All Contacts
   public List<Event> getAllContacts() {
      List<Event> eventList = new ArrayList<Event>();
      // Select All Query
      String selectQuery = "SELECT  * FROM " + TABLE_EVENTS;

      SQLiteDatabase db = this.getWritableDatabase();
      Cursor cursor = db.rawQuery(selectQuery, null);

      // looping through all rows and adding to list
      if (cursor.moveToFirst()) {
          do {

              Event event = new Event();
              event.set_Id(Integer.parseInt(cursor.getString(0)));
              event.set_title(cursor.getString(1));
              event.set_time(cursor.getString(2));
              event.set_date(cursor.getString(3));                          
              event.set_image(cursor.getBlob(4));
              eventList.add(event);
          } while (cursor.moveToNext());
      }

      // return contact list
      return eventList;
  }

// Getting event Count
    public int getEventsCount() {
        String countQuery = "SELECT  * FROM " + TABLE_EVENTS;
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(countQuery, null);
        cursor.close();

        // return count
        return cursor.getCount();
    }

 // Updating single contact
    public int updateEvent(Event event) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(KEY_TITLE, event.get_title());
        values.put(KEY_TIME, event.get_time());
        values.put(KEY_DATE, event.get_date());

        // updating row
        return db.update(TABLE_EVENTS, values, KEY_ID + " = ?",
                new String[] { String.valueOf(event.get_Id()) });
    }

    // Deleting single contact
    public void deleteEvent(Event event) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(TABLE_EVENTS, KEY_ID + " = ?",
                new String[] { String.valueOf(event.get_Id()) });
        db.close();
    }

}

Answer 1

Remember any onclick or ontouch or onitemlongclick etc... type of listener have their own context. To me you can define a global variable Context context and in your oncreate you can intialize it as context=this ( it should be outside any onclick or onitemlongclick etc.. things it should be in the main of oncreate ) now you can use this context in your whole class in longclick , Toast , constructors.... etc...

Also you didn't open the connection to db using db.open() before performing any database activity... thx

Answer 2

Change your

DatabaseHandler db = new DatabaseHandler(this);

with this one

DatabaseHandler db = new DatabaseHandler(getActivity());

Database handler requires context, when using inside the listView.setOnItemLongClickListener then this is not the same as of class this, so you should use getActivity() when using inside onClickListener.

Other possible solutions instead of getActivity()

1. MainActivity.this
2. MainActivity.getActivity()

Answer 3

Change -> DatabaseHandler db = new DatabaseHandler(this);

to DatabaseHandler db = new DatabaseHandler(MainActivity.this);