android room PageSource<Key, Value> 未加载任何内容

Question

我正在尝试使用jetpack库中的Paging3包从我的数据库中获取信息，但由于某种原因我无法使其工作，它根本不起作用，没有抛出任何错误，我也手动完成了所有操作，任何人都可以帮助我修复问题 ？ 我的房间道是

@Dao
interface ContactDao {
    @Insert
    fun insertAll(vararg contacts: Contact)

    @Query("SELECT * FROM contact WHERE id=:id")
    fun getById(id: Int): Contact?

    @Query("SELECT * FROM contact WHERE number=:number")
    fun getByNumber(number: String): Contact?

    @Query(
        """
SELECT 
    contact.id,
    contact.name,
    contact.number,
    MAX(contact_message.message_time) AS latest_message_time,
    COUNT(contact_message.id) as messages_count,
    contact_message.message_body as latest_message_body
FROM
    contact
INNER JOIN
    contact_message
ON
    contact_message.contact_id = contact.id
GROUP BY
    contact.id
ORDER BY
    latest_message_time DESC;
    """
    )
    fun getAll(): List<ContactWithCount>

    @Query(
        """
SELECT 
    contact.id,
    contact.name,
    contact.number,
    MAX(contact_message.message_time) AS latest_message_time,
    COUNT(contact_message.id) as messages_count,
    contact_message.message_body as latest_message_body
FROM
    contact
INNER JOIN
    contact_message
ON
    contact_message.contact_id = contact.id
GROUP BY
    contact.id
ORDER BY
    latest_message_time DESC;
    """
    )
    fun getAllWithPagination(): PagingSource<Int, ContactWithCount>
}

ViewModel 函数是

class SomeClass {
    @ExperimentalPagingApi
    fun getAllContactsPager(): Flow<PagingData<ContactWithCount>> {
        return Pager(
            config = PagingConfig(pageSize = 20),
        ) {
            db.contactDao().getAllWithPagination()
        }.flow.cachedIn(viewModelScope)

    }
}

我的 ui 撰写代码是

@OptIn(ExperimentalPagingApi::class)
@Composable
fun ContactsList(vm: SmsViewModel = viewModel()) {
    val pager = vm.getAllContactsPager().collectAsLazyPagingItems()
    LazyColumn(modifier = Modifier.fillMaxSize()) {
        items(
            count = pager.itemCount
        ) { index ->
            val item = pager[index]
            item?.let {
                ContactBasicInfoCard(vm = vm, contactWithCount = item)
            }
        }
    }
}

由于某种原因它没有加载任何数据

我尝试手动完成所有事情，但根本不起作用

Answer 1

模拟我可以通过从

;

 中删除 

@Query

分号来简单地解决问题

@Dao
interface ContactDao {
    @Insert
    fun insertAll(vararg contacts: Contact)

    @Query("SELECT * FROM contact WHERE id=:id")
    fun getById(id: Int): Contact?

    @Query("SELECT * FROM contact WHERE number=:number")
    fun getByNumber(number: String): Contact?

    @Query(
        """
SELECT 
    contact.id,
    contact.name,
    contact.number,
    MAX(contact_message.message_time) AS latest_message_time,
    COUNT(contact_message.id) as messages_count,
    contact_message.message_body as latest_message_body
FROM
    contact
INNER JOIN
    contact_message
ON
    contact_message.contact_id = contact.id
GROUP BY
    contact.id
ORDER BY
    latest_message_time DESC
    """
    )
    fun getAll(): List<ContactWithCount>

    @Query(
        """
SELECT 
    contact.id,
    contact.name,
    contact.number,
    MAX(contact_message.message_time) AS latest_message_time,
    COUNT(contact_message.id) as messages_count,
    contact_message.message_body as latest_message_body
FROM
    contact
INNER JOIN
    contact_message
ON
    contact_message.contact_id = contact.id
GROUP BY
    contact.id
ORDER BY
    latest_message_time DESC
    """
    )
    fun getAllWithPagination(): PagingSource<Int, ContactWithCount>
}