使用 savestate 保存 recyclerview 项目

Question

我目前正在编写一个显示电影列表的应用程序。该应用有 8 个片段包含回收视图：热门电影、动作片、喜剧片、恐怖片、浪漫片、科幻片、搜索和收藏夹。

recyclerview 中的项目包含一个复选框，用于将电影添加到收藏夹。当我滚动或退出应用程序时，复选框状态会重置。我正在尝试使用 savestate 保存复选框的状态，但它不起作用。

谁能告诉我我做错了什么？下面是视图模型。

谢谢。

MoviesListViewModel.kt

package com.example.moviesapp.ui

import androidx.lifecycle.*
import com.example.moviesapp.network.MoviesRepository
import com.example.moviesapp.network.MoviesResults
import dagger.hilt.android.lifecycle.HiltViewModel
import kotlinx.coroutines.launch
import javax.inject.Inject

const val DEFAULT_QUERY = " "
const val ACTION_MOVIES = "moviesAction"
const val COMEDY_MOVIES = "moviesComedy"
const val HORROR_MOVIES = "moviesHorror"
const val ROMANCE_MOVIES = "moviesRomance"
const val SCIFI_MOVIES = "moviesScifi"
const val TRENDING_MOVIES = "moviesTrending"


enum class MovieApiStatus {LOADING, ERROR, DONE}


@HiltViewModel
class MoviesListViewModel @Inject constructor(
    private val repository: MoviesRepository,
  private var state: SavedStateHandle

): ViewModel() {

       private val _moviesAction: MutableLiveData<List<MoviesResults.Movies>> = state.getLiveData(ACTION_MOVIES)
       val moviesAction: LiveData<List<MoviesResults.Movies>> = _moviesAction

       private val _moviesComedy: MutableLiveData<List<MoviesResults.Movies>> = state.getLiveData(COMEDY_MOVIES)
       val moviesComedy: LiveData<List<MoviesResults.Movies>> = _moviesComedy

       private val _moviesHorror: MutableLiveData<List<MoviesResults.Movies>> = state.getLiveData(HORROR_MOVIES)
       val moviesHorror: LiveData<List<MoviesResults.Movies>> = _moviesHorror

       private val _moviesRomance: MutableLiveData<List<MoviesResults.Movies>> = state.getLiveData(
           ROMANCE_MOVIES)
       val moviesRomance: LiveData<List<MoviesResults.Movies>> = _moviesRomance

       private val _moviesScifi: MutableLiveData<List<MoviesResults.Movies>> = state.getLiveData(SCIFI_MOVIES)
       val moviesScifi: LiveData<List<MoviesResults.Movies>> = _moviesScifi

    private val _moviesTrending: MutableLiveData<List<MoviesResults.Movies>> = state.getLiveData(TRENDING_MOVIES)
    val moviesTrending: LiveData<List<MoviesResults.Movies>> = _moviesTrending

    private val _networkState = MutableLiveData<MovieApiStatus>()
    val networkState: LiveData<MovieApiStatus> = _networkState





    init {
        getMovies()

    }




 fun getAction() {
     viewModelScope.launch {
         _moviesAction.value = repository.getActionMovies()
     }
 }

     fun getComedy() {
         viewModelScope.launch {
             _moviesComedy.value = repository.getComedyMovies()

         }

     }

    fun getHorror() {
        viewModelScope.launch {
            _moviesHorror.value = repository.getHorrorMovies()
        }

    }
    fun getRomance() {
        viewModelScope.launch {
            _moviesRomance.value = repository.getRomanceMovies()
        }

    }

    fun getScifi() {
        viewModelScope.launch {
            _moviesScifi.value = repository.getScifiMovies()

        }

    }

    fun getTrending() {
        viewModelScope.launch {
            _moviesTrending.value = repository.getTrendingMovies()
        }

    }









    private var currentQuery = MutableLiveData(DEFAULT_QUERY)







     val movies = currentQuery.switchMap {
            queryString ->
       liveData {
           emit(repository.getSearchResults(queryString))
       }
   }

    fun searchMovies(query: String) {

    currentQuery.value = query

    }

    private fun getMovies() {
        viewModelScope. launch {
            _networkState.value = MovieApiStatus.LOADING
            try {
                _networkState.value = MovieApiStatus.DONE
            }
            catch (e: Exception) {
                _networkState.value = MovieApiStatus.ERROR

            }

        }

    }



    class MoviesListViewModelFactory @Inject constructor(private val repository: MoviesRepository, private val state: SavedStateHandle): ViewModelProvider.Factory {
        override fun <T : ViewModel?> create(modelClass: Class<T>): T {
            if (modelClass.isAssignableFrom(MoviesListViewModel::class.java)) {
                @Suppress("UNCHECKED_CAST")
                return MoviesListViewModel(repository, state) as T
            }
            throw IllegalArgumentException("Unknown ViewModel class")

        }


    }



}

Answer 1

用于访问和修改 Context.getSharedPreferences(String, int) 返回的首选项数据的接口。对于任何特定的首选项集，所有客户端都共享一个此类的单个实例。对首选项的修改必须通过 Editor 对象，以确保首选项值保持一致状态并控制何时提交到存储。从各种 get 方法返回的对象必须被应用程序视为不可变对象。

注意：这个类提供了强大的一致性保证。它正在使用可能会降低应用程序速度的昂贵操作。频繁更改的属性或可以容忍损失的属性应使用其他机制。有关详细信息，请阅读 Editor.commit() 和 Editor.apply() 上的 cmets。

注意：该类不支持跨多个进程使用。

在您的情况下，您可以简单地存储键值对来记录相关选择。