Question

我正在尝试使用会议室数据库读取ID和名字，但是在运行应用程序之前出现了此错误：

未将架构导出目录提供给注释处理器，因此我们无法导出架构。您可以提供 room.schemaLocation注解处理器参数或设置 exportSchema为false。

如果我分别读取ID或名字，但不能同时读取ID和名，则没有问题

代码示例（这可以正常工作）

AppDatabase appDatabase;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_categories);
        ButterKnife.bind(this);
        appDatabase = Room.databaseBuilder(CategoriesActivity.this, AppDatabase.class, "RDatabase").allowMainThreadQueries().build();
        Log.w("name", appDatabase.userDao().getAll());
    }

    @Entity
    public class User {
        @PrimaryKey
        int uid;

        @ColumnInfo(name = "first_name")
        String firstName;
    }

    @Dao
    public interface UserDao {
        @Insert
        void insertAll(User... users);

        @Query("SELECT first_name FROM user")
        String getAll();
    }

    @Database(entities = {User.class}, version = 1)
    public abstract static class AppDatabase extends RoomDatabase {
        public abstract UserDao userDao();
    }

代码示例（由于我同时读取了id和名字，因此无法正常工作）

AppDatabase appDatabase;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_categories);
        ButterKnife.bind(this);
        appDatabase = Room.databaseBuilder(CategoriesActivity.this, AppDatabase.class, "RDatabase").allowMainThreadQueries().build();
        List<User> a = appDatabase.userDao().getAll();
        Log.w("aaa","" + a.get(0).uid);
    }

    @Entity
    public class User {
        @PrimaryKey
        int uid;

        @ColumnInfo(name = "first_name")
        String firstName;
    }

    @Dao
    public interface UserDao {
        @Insert
        void insertAll(User... users);

        @Query("SELECT uid,first_name FROM user")
        List<User> getAll();
    }

    @Database(entities = {User.class}, version = 1)
    public abstract static class AppDatabase extends RoomDatabase {
        public abstract UserDao userDao();
    }

我尝试将exportSchema to false放在版本之后，但出现此错误

错误：一个包含CategoriesActivity.User的封闭实例是必填

我无法读取会议室数据库中的几列

0 个答案: