问题可能出在数据加载和适配器更新之间的异步操作上。以下是示例代码来解决此问题:
Kotlin代码:
class MyViewModel: ViewModel() {
private val _myData = MutableLiveData>>()
val myData: LiveData>> = _myData
fun loadData() {
val pager = Pager(
config = PagingConfig(pageSize = 10),
pagingSourceFactory = { MyPagingSource() }
)
val data = pager.liveData.cachedIn(viewModelScope)
_myData.postValue(data)
}
}
class MyAdapter: PagingDataAdapter(MyModel.DIFF_CALLBACK) {
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
val item = getItem(position)
if (item != null) {
holder.bind(item)
}
}
}
class MyFragment: Fragment() {
private lateinit var binding: FragmentMyBinding
private lateinit var viewModel: MyViewModel
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View {
binding = FragmentMyBinding.inflate(inflater, container, false)
viewModel = ViewModelProvider(this).get(MyViewModel::class.java)
val myAdapter = MyAdapter()
viewModel.myData.observe(viewLifecycleOwner, Observer {
myAdapter.submitData(viewLifecycleOwner.lifecycle, it.valueOrNull())
})
return binding.root
}
}
这里,我们创建了一个MyViewModel
和一个MyAdapter
,并在MyFragment
中使用它们。当loadData
函数被调用时,我们使用Pager
和PagingConfig
创建一个PagingData
对象,然后将它的LiveData
值存储在我们的_myData
变量中。在MyFragment
中,我们使用observe
函数观察_myData
变量,并在回调函数中使用submitData
函数更新适配器。
关键点在于,在submitData
调用之前,我们必须确保数据已正确加载。