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。