SQLIte inserting null instead of the desired value

I am trying to insert a value into a SQLite table, but when I fetch that value, it looks like null is getting inserted instead.

The call to insert the row is given as:

@Override
public void onClick(View v) {
    Deck deck = new Deck(mDeckNameText.getText().toString());
    db.addDeck(deck);
    }

The addDeck method in to insert the row (which is in my database handler) is as follows:

void addDeck(Deck deck) {
    SQLiteDatabase db = this.getWritableDatabase();

    ContentValues values = new ContentValues();
    values.put(KEY_DECK_NAME, deck.getDeckName());

    db.insert(TABLE_DECKS,null,values);
}

Where the Deck class is defined as:

public class Deck {

    int _deck_id;
    String _deck_name;

    public Deck(){
    }

    public Deck(String deck_name) {
        this._deck_name = deck_name;
    }

    public Deck(int deck_id, String deck_name) {
        this._deck_id = deck_id;
        this._deck_name = deck_name;
    }

    //get deck_id
    public int getDeckId(){
        return this._deck_id;
    }

    //set deck_id
    public void setDeckId(int deck_id){
        this._deck_id = deck_id;
    }

    //get deck name
    public String getDeckName(){
        return this._deck_name;
    }

    //set deck name
    public void setDeckName(String deck_name){
        this._deck_name = deck_name;
    }
}

The table that contains the decks is created in the following method:

public void onCreate(SQLiteDatabase db) {
    String CREATE_DECKS_TABLE = "CREATE TABLE "+TABLE_DECKS+"("
            +KEY_DECK_ID+" INTEGER PRIMARY KEY, "+KEY_DECK_NAME
            +" TEXT"+")";

    db.execSQL(CREATE_DECKS_TABLE);
}

The log output I get when I fetch the deck ids and deck names from the rows in my table looks something like this (after the third attempt at inserting a deck):

D/ID:﹕ 1

D/Name:﹕ null

D/ID:﹕ 2

D/Name:﹕ null

D/ID:﹕ 3

D/Name:﹕ null

Any idea why the name is coming back as null?

Thank you in advance.