我的db有問題。沒有任何表和數據，只有空數據庫。我應該在代碼中更改什么？我想用硬編碼的值創建一個數據庫，因為我想稍后在spinner中使用它們。Database class    public class Database extends SQLiteOpenHelper {    private static final String DATABASE_NAME = "CurrencyExchange.db";    private static final String CURRENCY_TABLE = "currency_table";    public Database(Context context) {    super(context, DATABASE_NAME, null, 1);}@Overridepublic void onCreate(SQLiteDatabase db) {    db.execSQL("CREATE TABLE "+CURRENCY_TABLE+ " ( ID INTEGER PRIMARY KEY AUTOINCREMENT, BGN TEXT, NZD TEXT, ILS TEXT, RUB TEXT, CAD TEXT, USD TEXT, PHP TEXT, CHF TEXT, ZAR TEXT, AUD TEXT, JPY TEXT, TRY TEXT, HKD TEXT, MYR TEXT, THB TEXT, HRK TEXT, NOK TEXT, IDR TEXT, DKK TEXT, CZK TEXT, HUF TEXT, GBP TEXT, MXN TEXT, KRW TEXT, ISK TEXT, SGD TEXT, BRL TEXT, PLN TEXT, INR TEXT, RON TEXT, CNY TEXT, SEK TEXT)");}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {    db.execSQL("DROP TABLE IF EXISTS "+CURRENCY_TABLE);    onCreate(db);}public boolean insertData(){    SQLiteDatabase database = this.getWritableDatabase();    ContentValues contentValues = new ContentValues();    final String insert_data = "INSERT INTO "+CURRENCY_TABLE+ " VALUES (0,'BGN','NZD','ILS','RUB','CAD','USD','PHP','CHF','ZAR','AUD','JPY','TRY','HKD','MYR','THB','HRK','NOK','IDR','DKK','CZK','HUF','GBP','MXN','KRW','ISK','SGD','BRL','PLN','INR','RON','CNY','SEK')";    contentValues.put(CURRENCY_TABLE, insert_data);    return database.insert(CURRENCY_TABLE, null, contentValues) != -1;}主要活動    public class MainActivity extends AppCompatActivity {Database database;@Overrideprotected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    database = new Database(this);    database.insertData();