安卓加数据库源码

// 创建一个继承自SQLiteOpenHelper的类
public class DatabaseHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "MyDatabase.db";
    private static final int DATABASE_VERSION = 1;
    public static final String TABLE_NAME = "users";
    public static final String COLUMN_ID = "_id";
    public static final String COLUMN_NAME = "name";

    // 构造函数
    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    // 创建表
    @Override
    public void onCreate(SQLiteDatabase db) {
        String createTableQuery = "CREATE TABLE " + TABLE_NAME + " (" +
                COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                COLUMN_NAME + " TEXT NOT NULL);";
        db.execSQL(createTableQuery);
    }

    // 升级数据库
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
        onCreate(db);
    }

    // 插入数据
    public long insertUser(String name) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(COLUMN_NAME, name);
        return db.insert(TABLE_NAME, null, values);
    }

    // 查询数据
    public Cursor getUsers() {
        SQLiteDatabase db = this.getReadableDatabase();
        return db.query(TABLE_NAME, null, null, null, null, null, null);
    }
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    if (oldVersion < 2) {
        // 执行一些升级操作，比如添加新列
        db.execSQL("ALTER TABLE " + TABLE_NAME + " ADD COLUMN new_column TEXT");
    }
    // 如果需要更复杂的升级逻辑，可以在这里实现
}