感谢@Đặng Anh Hào,我才能够走上正轨。由于我的光标是 String 而不是 Int,因此分页源加载函数如下所示:
override suspend fun load(params: LoadParams<String>): LoadResult<String, Order> {
return try{
val response = service.getOrders(query,params.key?:"",10)
val nextKey = if(response.paging?.cursors?.after=="false") null else response.paging?.cursors?.after
val prevKey = if(response.paging?.cursors?.before=="false") null else response.paging?.cursors?.before
LoadResult.Page(response.data?.toOrderList()?:emptyList(),prevKey,nextKey)
}catch (exception: IOException) {
LoadResult.Error(exception)
} catch (exception: retrofit2.HttpException) {
LoadResult.Error(exception)
}
}
onrefreshkey 看起来像这样:
override fun getRefreshKey(state: PagingState<String, Order>): String? {
return state.anchorPosition?.let {
state.closestItemToPosition(it)?.orderId
}
}
存储库方法如下所示:
fun getOrdersPaginated(storeId: String): Flow<PagingData<Order>> {
return Pager(
config = PagingConfig(enablePlaceholders = false,pageSize = 10),
pagingSourceFactory = {PagingSource(apiService,storeId)}
).flow
}
而View Model方法是这样的:
private val _pagedOrders = MutableLiveData<PagingData<Order>>()
val orders get() = _pagedOrders
private var currentQueryValue: String? = null
private var currentSearchResult: Flow<PagingData<Order>>? = null
fun getOrdersPaginated(storeId: String) {
viewModelScope.launch {
currentQueryValue = storeId
val newResult: Flow<PagingData<Order>> = repository.getOrdersPaginated(storeId)
.cachedIn(viewModelScope)
currentSearchResult = newResult
currentSearchResult!!.collect {
_pagedOrders.value = it
}
}
}
该活动像这样调用分页:
private var searchJob: Job? = null
private fun getOrders() {
viewModel.getOrdersPaginated(storeId)
}
private fun listenForChanges() {
viewModel.orders.observe(this, {
searchJob?.cancel()
searchJob = lifecycleScope.launch {
ordersAdapter.submitData(it)
}
})
}
最后,适配器与 ListAdapter 相同,唯一的变化是它现在扩展了PagingDataAdapter<Order, OrderAdapter.ViewHolder>(OrdersDiffer)
有关如何操作的更详细教程,我读了这个代码实验室 https://developer.android.com/codelabs/android-paging#0