在安卓SQLite数据库中保存用户名和密码的程序

// 创建数据库和表
public class DBHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "UserDB";
    private static final int DATABASE_VERSION = 1;
    private static final String TABLE_NAME = "User";
    private static final String COLUMN_USERNAME = "username";
    private static final String COLUMN_PASSWORD = "password";

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

    @Override
    public void onCreate(SQLiteDatabase db) {
        String createTableQuery = "CREATE TABLE " + TABLE_NAME + " (" +
                COLUMN_USERNAME + " TEXT PRIMARY KEY, " +
                COLUMN_PASSWORD + " TEXT)";
        db.execSQL(createTableQuery);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // 升级数据库时的操作
    }
}

// 插入数据
public class UserDAO {
    private DBHelper dbHelper;

    public UserDAO(Context context) {
        dbHelper = new DBHelper(context);
    }

    public void insertUser(String username, String password) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(DBHelper.COLUMN_USERNAME, username);
        values.put(DBHelper.COLUMN_PASSWORD, password);
        db.insert(DBHelper.TABLE_NAME, null, values);
        db.close();
    }
}

// 验证用户名和密码
public class UserDAO {
    private DBHelper dbHelper;

    public UserDAO(Context context) {
        dbHelper = new DBHelper(context);
    }

    public boolean validateUser(String username, String password) {
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        String[] columns = {DBHelper.COLUMN_USERNAME, DBHelper.COLUMN_PASSWORD};
        String selection = DBHelper.COLUMN_USERNAME + " = ? AND " + DBHelper.COLUMN_PASSWORD + " = ?";
        String[] selectionArgs = {username, password};
        Cursor cursor = db.query(DBHelper.TABLE_NAME, columns, selection, selectionArgs, null, null, null);
        boolean isValid = cursor.moveToFirst();
        cursor.close();
        db.close();
        return isValid;
    }
}