public long addUser(String user, String password) { SQLiteDatabase db = this.getWritableDatabase(); ContentValues contentValues = new ContentValues(); contentValues.put("username", user); contentValues.put("password", password); long res = db.insert("registeruser", null, contentValues); db.close(); return res; }

这段代码是在Android中使用SQLite数据库进行数据存储时，添加新用户记录的方法。

首先，通过调用getWritableDatabase()方法获取可写的数据库对象。然后，创建一个ContentValues对象，用于存储需要添加的记录，将用户名和密码分别存储到ContentValues对象中。接着，调用insert()方法，将ContentValues对象中的数据插入到"registeruser"表中。在执行插入操作后，会返回一个长整型的数值，表示插入新记录的行号。最后，通过调用close()方法关闭数据库连接，并返回插入记录的行号。

在实际编程中，可以通过调用这个方法来将用户注册时输入的用户名和密码添加到数据库中，以便后续进行登录验证等操作。

相关问题

android studio数据库增删查改

在 Android Studio 中进行数据库的增删查改操作，需要使用 SQLite 数据库，以下是一个简单的示例：

1. 创建数据库表

public class MyDatabaseHelper extends SQLiteOpenHelper {
    private static final String DB_NAME = "mydb";
    private static final int DB_VERSION = 1;

    public MyDatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE IF NOT EXISTS user (_id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, age INTEGER)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS user");
        onCreate(db);
    }
}

2. 添加数据

public void addUser(String name, int age) {
    SQLiteDatabase db = dbHelper.getWritableDatabase();
    ContentValues values = new ContentValues();
    values.put("name", name);
    values.put("age", age);
    db.insert("user", null, values);
    db.close();
}

3. 删除数据

public void deleteUser(int id) {
    SQLiteDatabase db = dbHelper.getWritableDatabase();
    db.delete("user", "_id=?", new String[]{String.valueOf(id)});
    db.close();
}

4. 修改数据

public void updateUser(int id, String name, int age) {
    SQLiteDatabase db = dbHelper.getWritableDatabase();
    ContentValues values = new ContentValues();
    values.put("name", name);
    values.put("age", age);
    db.update("user", values, "_id=?", new String[]{String.valueOf(id)});
    db.close();
}

5. 查询数据

public List<User> queryUsers() {
    SQLiteDatabase db = dbHelper.getReadableDatabase();
    Cursor cursor = db.query("user", null, null, null, null, null, null);
    List<User> userList = new ArrayList<>();
    while (cursor.moveToNext()) {
        int id = cursor.getInt(cursor.getColumnIndex("_id"));
        String name = cursor.getString(cursor.getColumnIndex("name"));
        int age = cursor.getInt(cursor.getColumnIndex("age"));
        User user = new User(id, name, age);
        userList.add(user);
    }
    cursor.close();
    db.close();
    return userList;
}

以上是一个简单的示例，实际项目中需要根据具体需求进行修改和完善。

android studio完成添加、查询、修改、删除功能代码

以下是一个基本的 Android Studio 的增删查改功能示例代码，示例使用 SQLite 数据库进行数据存储：

1. 创建数据库帮助类 DBHelper.java

public class DBHelper extends SQLiteOpenHelper {
    private static final String DB_NAME = "my_db";
    private static final int DB_VERSION = 1;

    public DBHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String sql = "CREATE TABLE IF NOT EXISTS user(id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, age INTEGER)";
        db.execSQL(sql);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        String sql = "DROP TABLE IF EXISTS user";
        db.execSQL(sql);
        onCreate(db);
    }
}

2. 创建增删查改的操作类 UserDao.java

public class UserDao {
    private DBHelper dbHelper;

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

    public void addUser(User user) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put("name", user.getName());
        values.put("age", user.getAge());
        db.insert("user", null, values);
        db.close();
    }

    public List<User> getAllUsers() {
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        List<User> userList = new ArrayList<>();
        Cursor cursor = db.query("user", null, null, null, null, null, null);
        while (cursor.moveToNext()) {
            int id = cursor.getInt(cursor.getColumnIndex("id"));
            String name = cursor.getString(cursor.getColumnIndex("name"));
            int age = cursor.getInt(cursor.getColumnIndex("age"));
            User user = new User(id, name, age);
            userList.add(user);
        }
        cursor.close();
        db.close();
        return userList;
    }

    public User getUserById(int id) {
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        Cursor cursor = db.query("user", null, "id=?", new String[]{String.valueOf(id)}, null, null, null);
        User user = null;
        if (cursor.moveToFirst()) {
            String name = cursor.getString(cursor.getColumnIndex("name"));
            int age = cursor.getInt(cursor.getColumnIndex("age"));
            user = new User(id, name, age);
        }
        cursor.close();
        db.close();
        return user;
    }

    public void updateUser(User user) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put("name", user.getName());
        values.put("age", user.getAge());
        db.update("user", values, "id=?", new String[]{String.valueOf(user.getId())});
        db.close();
    }

    public void deleteUserById(int id) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        db.delete("user", "id=?", new String[]{String.valueOf(id)});
        db.close();
    }
}

3. 创建实体类 User.java

public class User {
    private int id;
    private String name;
    private int age;

    public User(int id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

4. 在 Activity 中调用增删查改操作

public class MainActivity extends AppCompatActivity {
    private UserDao userDao;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        userDao = new UserDao(this);

        // 添加用户
        User user1 = new User(1, "Tom", 20);
        userDao.addUser(user1);

        // 获取所有用户
        List<User> userList = userDao.getAllUsers();
        for (User user : userList) {
            Log.i("MainActivity", "id: " + user.getId() + ", name: " + user.getName() + ", age: " + user.getAge());
        }

        // 修改用户
        User user2 = new User(1, "Jerry", 22);
        userDao.updateUser(user2);

        // 删除用户
        userDao.deleteUserById(1);

        // 获取指定用户
        User user3 = userDao.getUserById(2);
        if (user3 != null) {
            Log.i("MainActivity", "id: " + user3.getId() + ", name: " + user3.getName() + ", age: " + user3.getAge());
        }
    }
}