使用savestate保存回收视图项目

Question

我目前正在编写一个显示电影列表的应用程序。该应用程序有8个片段，其中包含回收视图:热门电影、动作、喜剧、恐怖、浪漫、科幻、搜索和收藏。

回收器视图中的项目包含一个将电影添加到收藏夹的复选框。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。

有人能告诉我我哪里做错了吗？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

用于访问和修改由Context.getSharedPreferences(String，返回的首选项数据的接口( int)。对于任何特定的首选项集，都有一个所有客户端共享的类的单个实例。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，并控制它们何时提交到存储。应用程序必须将从各种get方法返回的对象视为不可变对象。

注意:这个类提供了很强的一致性保证。它正在使用昂贵的操作，这可能会减慢应用程序的速度。经常更改属性或可以容忍损失的属性应该使用其他机制。有关更多详细信息，请阅读Editor.commit()和Editor.apply().上的评论

注意:这个类不支持跨多个进程使用。

在您的例子中，您可以简单地存储键-值对来记录相关的选择。