为什么我的分页源没有给我任何数据？

Question

不起作用的项目元素

我检查数据是否为空，并在片段中执行默认的submitList。

顺便说一句，这是文档的链接

搜索寻呼源

这些日志甚至没有显示

class SearchPagingSource(
private val api: Api,
private val query: String
) : PagingSource<Int, Image>
() {
override suspend fun load(params: LoadParams<Int>): LoadResult<Int, Image> {
val position = params.key ?: 0
Log.d("SUPERTAG", "response")
return try {
val response =
api.search(query, position, params.loadSize, Locale.getDefault().language)
val list = ArrayList<Image>()
response.gif.forEach {
list.add(it.image)
}
Log.d("SUPERTAG", "response: $list")
LoadResult.Page(
data = list,
prevKey = null,
nextKey = if (list.isEmpty()) null else position + 15
)
} catch (e: IOException) {
// no connection
Log.d("SUPERTAG", "IOException: ${e.message}")
LoadResult.Error(e)
} catch (e: HttpException) {
// error loading
Log.d("SUPERTAG", "HttpException: ${e.message}")
LoadResult.Error(e)
}
}
}

ViewModel

Null，因为存储库返回了Null。

class SearchViewModel : ViewModel() {
private val searchRepository = SearchRepository.getInstance()
private val _query = MutableLiveData<String>()
private val _results = _query.map { data ->
searchRepository.search(data).value
}
val results = _results
private val _error = MutableLiveData<String>()
val error: LiveData<String> = _error
@SuppressLint("StaticFieldLeak")
private lateinit var progressBar: ProgressBar
fun initProgress(progress: ProgressBar) {
progressBar = progress
}
fun search(query: String, errorLoading: String) {
viewModelScope.launch {
try {
progressBar.visibility = View.VISIBLE
_query.value = query
Log.d("SUPERTAG", "result2: ${searchRepository.search(_query.value!!).value}")
progressBar.visibility = View.GONE
} catch (e: Exception) {
_error.value = e.message
}
}
}
}

Repository正是这部分代码返回null，我通过日志检查了它。我想我在参数或一般情况下都做错了。

object SearchRepository {
private lateinit var instance: SearchRepository
private val app: App by lazy {
App().getInstance()
}
fun getInstance(): SearchRepository {
instance = this
app.initRetrofit()
return instance
}
fun search(query: String) = Pager(
config = PagingConfig(
15,
maxSize = 50,
enablePlaceholders = false
),
pagingSourceFactory = {
SearchPagingSource(app.api, query)
}
).liveData
}

如果我真的喜欢这样，我至少会得到小吃条和一个错误。通常它什么都不显示，甚至没有进度条所以，如果我添加jumpThreshold=0，我会得到一个包含错误的snackbar，这是我通常不会遇到的。

fun search(query: String) = Pager(
config = PagingConfig(
pageSize = 15,
jumpThreshold = 0
),
pagingSourceFactory = {
SearchPagingSource(app.api, query)
}
).liveData

编辑

所以，我用flow做了这件事，它有点奏效，但我仍然没有在我的回收商那里得到一份清单。

存储库

fun getListData(query: String): Flow<PagingData<Image>> {
return Pager(
config = PagingConfig(
pageSize = 15,
maxSize = 50,
enablePlaceholders = true
), pagingSourceFactory = {
SearchPagingSource(query = query, api = app.api)
}).flow
}

ViewModel

fun search(query: String){
viewModelScope.launch {
try {
searchRepository.getListData(query).collectLatest {
it.map {
Log.d("SUPERTAG", "image $it")
}
Log.d("SUPERTAG", it.toString())
_results.value = it
}
} catch (e: Exception){
_error.value = e.message
}
}
}

Answer 1

答案在适配器中！

class SearchAdapter(
diffCallback: DiffUtil.ItemCallback<Image>,
private val clickListener: (url: String) -> Unit
) : PagingDataAdapter<Image, SearchAdapterViewHolder>(diffCallback) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): SearchAdapterViewHolder {
val inflater = LayoutInflater.from(parent.context)
val view = inflater.inflate(R.layout.list_item, parent, false)
return SearchAdapterViewHolder(view)
}
override fun onBindViewHolder(holder: SearchAdapterViewHolder, position: Int) {
val item = getItem(position)
if(item != null){
holder.imageView.setOnClickListener {
clickListener(item.original.url)
}
holder.bind(item)
}
}
}