要使用Android Jetpack Paging 3和Room的PagingSource,你可以按照以下步骤进行操作:
dependencies {
// Paging 3
implementation "androidx.paging:paging-runtime-ktx:3.0.1"
// Room
implementation "androidx.room:room-runtime:2.3.0"
kapt "androidx.room:room-compiler:2.3.0"
}
@Dao
interface UserDao {
@Query("SELECT * FROM User")
fun getUsers(): PagingSource
}
class UserPagingSource(private val userDao: UserDao) : PagingSource() {
override suspend fun load(params: LoadParams): LoadResult {
try {
// 从数据库中获取用户数据
val page = params.key ?: 1
val users = userDao.getUsers()
// 返回分页数据
return LoadResult.Page(
data = users,
prevKey = if (page > 1) page - 1 else null,
nextKey = page + 1
)
} catch (e: Exception) {
// 加载数据出错
return LoadResult.Error(e)
}
}
}
class UserViewModel(private val userDao: UserDao) : ViewModel() {
val users: Flow> = Pager(config = PagingConfig(pageSize = 20)) {
UserPagingSource(userDao)
}.flow
}
class UserFragment : Fragment() {
private val viewModel: UserViewModel by viewModels()
private lateinit var adapter: UserAdapter
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
adapter = UserAdapter()
// 观察PagingData流并更新适配器
viewLifecycleOwner.lifecycleScope.launch {
viewModel.users.collectLatest { pagingData ->
adapter.submitData(pagingData)
}
}
// 设置RecyclerView的适配器
recyclerView.adapter = adapter
}
}
这样,你就可以使用Android Jetpack Paging 3和Room的PagingSource来实现分页加载数据了。当RecyclerView滚动到底部时,Paging库会自动加载更多数据。