添加依赖
implementation ("androidx.paging:paging-compose:1.0.0-alpha08")
implementation ("com.google.accompanist:accompanist-swiperefresh:0.9.0")
定义Item内容
非常简单的一个标题和内容
data class Content(val title:String,val content: String)
定义RetrofitService
interface RetrofitService {
@GET("getContent")
suspend fun getContentByTitle(@Query("page") page: Int, @Query("title") title: String): AgResponse<List<Content>>
}
定义PagingSource
class ContentPageSource(val title: String, private val mService: RetrofitService) : PagingSource<Int,Content>(){
override suspend fun load(params: LoadParams<Int>): LoadResult<Int, Content> {
val key=params.key?:0
val resource = exeRequest {
mService.getContentByTitle(key, title)
}
return if (resource is Resource.SuccessResource) {
resource.data?.let {
return LoadResult.Page(
it, null, if (key > 8) {//这里是假设获取了8页之后就没有下一页了
null
} else {
key + 1
}
)
}
LoadResult.Error(Exception())
} else {
LoadResult.Error(Exception())
}
}
override fun getRefreshKey(state: PagingState<Int, Content>): Int? {
return null
}
}
Repository
class HomeRepository(private val mService:RetrofitService) {
fun getContentByTitle(title:String)=Pager(config = PagingConfig(20)){
ContentPageSource(title,mService)
}
}
ViewModel
class HomeViewModel(private val homeRepository: HomeRepository) : BaseViewModel() {
fun getContentByTitle(title: String): Flow<PagingData<Content>> {
return homeRepository.getContentByTitle(title).flow.cachedIn(viewModelScope)
}
}
对SwipeRefresh和Paging封装
@Composable
fun <T : Any> SwipeRefreshList(collectAsLazyPagingItems: LazyPagingItems<T>, content: LazyListScope.() -> Unit) {
val rememberSwipeRefreshState = rememberSwipeRefreshState(isRefreshing = false)
SwipeRefresh(
state = rememberSwipeRefreshState,
onRefresh = { collectAsLazyPagingItems.refresh() }) {
rememberSwipeRefreshState.isRefreshing =
collectAsLazyPagingItems.loadState.refresh is LoadState.Loading
LazyColumn(
modifier = Modifier
.fillMaxHeight()
.fillMaxWidth(),
horizontalAlignment = Alignment.CenterHorizontally
) {
content()
collectAsLazyPagingItems.apply {
when {
loadState.append is LoadState.Loading -> {//加载更多时，就在底部显示loading的item
item { LoadingItem() }
}
loadState.append is LoadState.Error -> {//加载更多的时候出错了，就在底部显示错误的item
item {
ErrorItem() {
collectAsLazyPagingItems.retry()
}
}
}
loadState.refresh is LoadState.Error -> {
if (collectAsLazyPagingItems.itemCount <= 0) {//刷新的时候，如果itemCount小于0，说明是第一次进来，出错了显示一个大的错误内容
item {
ErrorContent() {
collectAsLazyPagingItems.retry()
}
}
} else {
item {
ErrorItem() {
collectAsLazyPagingItems.retry()
}
}
}
}
}
}
}
}
}
@Composable
fun ErrorItem(retry: () -> Unit) {
Button(onClick = { retry() }, modifier = Modifier.padding(10.dp)) {
Text(text = "重试")
}
}
@Composable
fun ErrorContent(retry: () -> Unit) {
Image(modifier = Modifier.padding(top = 80.dp),painter = painterResource(id = R.drawable.bg_empty), contentDescription = null)
Text(text = "请求出错啦")
Button(onClick = { retry() }, modifier = Modifier.padding(10.dp)) {
Text(text = "重试")
}
}
@Composable
fun LoadingItem() {
CircularProgressIndicator(modifier = Modifier.padding(10.dp))
}
在Compose里使用
@Composable
fun RecommendContent(selectedTabIndex: Int, tabTitle: List<TabTitle>?) {
val homeViewModel: HomeViewModel = getViewModel()//使用koin注入viewModel
val collectAsLazyPagingItems =
homeViewModel.getContentByTitle("标题").collectAsLazyPagingItems()
SwipeRefreshList(collectAsLazyPagingItems){
items(collectAsLazyPagingItems) {
it?.let {
Column {
Text(text = it.title, style = MaterialTheme.typography.h6)
Text(text = it.content)
Divider()
}
}
}
}
}
