与升级 ORMLite 模式混淆

Question

我在 table account 中添加了一列 (description)。我还阅读了 this guild 来升级我的数据库。但是，我对这段代码中的 getHelper() 方法有点困惑：

Dao<Account, Integer> dao = getHelper().getAccountDao();
// change the table to add a new column named "description" 
dao.executeRaw("ALTER TABLE `account` ADD COLUMN description INTEGER;");

它是从哪里来的？我没有看到我的 DatabaseHelper class 中声明了 getHelper()。有人可以帮助我吗？

Answer 1

您应该有一个 class 扩展 OrmLiteSqliteOpenHelper，您可以在其中创建表（在 onCreate 中）并更新它们（在 onUpgrade 中）：

public class DatabaseHelper extends OrmLiteSqliteOpenHelper {

    public DatabaseHelper(Context context) {
        super(context, "database.db", null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase database, ConnectionSource connectionSource) {
        try {
           TableUtils.createTable(connectionSource, Account.class);
        } catch (SQLException e) {
            throw new RuntimeException("Error when create database tables", e);
        }
    }

    @Override
    public void onUpgrade(SQLiteDatabase database, ConnectionSource connectionSource, int oldVersion, int newVersion) {
        database.execSQL("ALTER TABLE `account` ADD COLUMN description INTEGER;");

        //same as:
        //AccountDAO dao = getDao(Acount.class);
        //dao.executeRaw("ALTER TABLE 'account' ADD COLUMN description INTEGER;");
    }
}

OrmLiteBaseListActivity, OrmLiteBaseService and OrmLiteBaseTabActivity provide a method getHelper to access the database helper whenever it is needed and will automatically create the helper in the onCreate() method and release it in the onDestroy() method.

此外，如果你使用上面的classes，你应该有这样的东西：

public class MyACtivity extends OrmLiteBaseActivity<DatabaseHelper> {

    //In this class, you can call getHelper() to obtain the DatabaseHelper instance 

}

与升级 ORMLite 模式混淆

Confusing with upgrading ORMLite schema

android

ormlite