Android 使用Google'；s分页库

我在一个回收视图中有一个简单的口袋妖怪列表，只有口袋妖怪的名字和一个“最喜欢的”按钮。我正在使用Android JetPack的分页库和PageKeyedDataSource来检索Pokemon的小块并将它们显示给用户。我只希望在活动未被销毁的情况下数据保持不变（即，我不希望将数据保持到文件室或数据库中，而是希望在ViewModel处于活动状态时数据保持不变）

我希望能够单击任何口袋妖怪项目上的心脏按钮，并将SimpleKeyon模型中的“isFavorite”字段更新为

true

或

false

。根据我的理解，如果我想更改该页面列表中的单个项目，我需要使数据源无效，从理论上讲，这应该生成页面列表的新LiveData，该数据可以馈送到适配器并显示在屏幕上

问题：如何使用页面库更新页面列表中的单个项目，而不需要空间或其他数据库？

将来，我想将这个解决方案扩展到一个用户可以喜欢帖子的社交媒体提要，但我不知道在数据库（如Room）中存储社交提要项目是否必要（或有效），因为这些提要项目在不断变化。因此，我选择将它们存储在ViewModel中，然后在用户每次退出应用程序时清除它们

以下是我目前的代码：

SimplePokemon.kt:

data class SimplePokemon(
    @SerializedName("name") val name: String,
    @SerializedName("url") val url: String,
    var isFavorite: Boolean = false
)

class PokemonViewModel(application: Application) : AndroidViewModel(application) {

    private val config = PagedList.Config.Builder()
        .setPageSize(20)
        .setEnablePlaceholders(false)
        .build()

    private fun initializedPagedListBuilder(config: PagedList.Config): LivePagedListBuilder<String, SimplePokemon> {
        val dataSourceFactory = object : DataSource.Factory<String, SimplePokemon>() {
            override fun create(): DataSource<String, SimplePokemon> {
                return PokemonDataSource()
            }
        }
        return LivePagedListBuilder<String, SimplePokemon>(dataSourceFactory, config)
    }

    fun pokemonPagedListLiveData(): LiveData<PagedList<SimplePokemon>> {
        return initializedPagedListBuilder(config).build()
    }
}

class PokemonAdapter :
    PagedListAdapter<SimplePokemon, PokemonAdapter.PokemonViewHolder>(PokemonDiffUtil()) {

    inner class PokemonViewHolder(v: View) : RecyclerView.ViewHolder(v) {
        private val pokemonNameTextView: TextView = v.findViewById(R.id.pokemon_name_text_view)
        private val pokemonFavoriteToggle: ToggleButton =
            v.findViewById(R.id.pokemon_favorite_toggle_button)

        fun bind(data: SimplePokemon) {
            pokemonNameTextView.text = data.name
            pokemonFavoriteToggle.isChecked = data.isFavorite
        }
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): PokemonViewHolder {
        val view =
            LayoutInflater.from(parent.context).inflate(R.layout.item_simple_pokemon, parent, false)
        return PokemonViewHolder(view)
    }

    override fun onBindViewHolder(holder: PokemonViewHolder, position: Int) {
        val item = getItem(position)
        item?.let { holder.bind(it) }
    }
}

class PokemonDataSource : PageKeyedDataSource<String, SimplePokemon>() {

    private val api = NetworkService.pokemonNetworkInterface

    override fun loadInitial(
        params: LoadInitialParams<String>,
        callback: LoadInitialCallback<String, SimplePokemon>
    ) {
        api.getPokemon().enqueue(object : Callback<PokeResponse<List<SimplePokemon>>> {

            override fun onFailure(call: Call<PokeResponse<List<SimplePokemon>>>?, t: Throwable?) {
                Log.e("PokemonDataSource", "Failed to fetch data!")
            }

            override fun onResponse(
                call: Call<PokeResponse<List<SimplePokemon>>>?,
                response: Response<PokeResponse<List<SimplePokemon>>>
            ) {
                val listing = response.body()
                val pokemon = listing?.results
                callback.onResult(pokemon ?: listOf(), listing?.previous, listing?.next)
            }
        })
    }

    override fun loadAfter(
        params: LoadParams<String>,
        callback: LoadCallback<String, SimplePokemon>
    ) {
        api.getPokemon(url = params.key)
            .enqueue(object : Callback<PokeResponse<List<SimplePokemon>>> {
                override fun onFailure(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    t: Throwable?
                ) {
                    Log.e("PokemonDataSource", "Failed to fetch data! Oh Noooo!")
                }

                override fun onResponse(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    response: Response<PokeResponse<List<SimplePokemon>>>
                ) {
                    val listing = response.body()
                    val pokemon = listing?.results
                    callback.onResult(pokemon ?: listOf(), listing?.next)
                }
            })
    }

    override fun loadBefore(
        params: LoadParams<String>,
        callback: LoadCallback<String, SimplePokemon>
    ) {
        api.getPokemon(url = params.key)
            .enqueue(object : Callback<PokeResponse<List<SimplePokemon>>> {
                override fun onFailure(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    t: Throwable?
                ) {
                    Log.e("PokemonDataSource", "Failed to fetch data! Oh Noooo!")
                }

                override fun onResponse(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    response: Response<PokeResponse<List<SimplePokemon>>>
                ) {
                    val listing = response.body()
                    val pokemon = listing?.results
                    callback.onResult(pokemon ?: listOf(), listing?.previous)
                }
            })
    }

PokemonViewModel.kt:

data class SimplePokemon(
    @SerializedName("name") val name: String,
    @SerializedName("url") val url: String,
    var isFavorite: Boolean = false
)

class PokemonViewModel(application: Application) : AndroidViewModel(application) {

    private val config = PagedList.Config.Builder()
        .setPageSize(20)
        .setEnablePlaceholders(false)
        .build()

    private fun initializedPagedListBuilder(config: PagedList.Config): LivePagedListBuilder<String, SimplePokemon> {
        val dataSourceFactory = object : DataSource.Factory<String, SimplePokemon>() {
            override fun create(): DataSource<String, SimplePokemon> {
                return PokemonDataSource()
            }
        }
        return LivePagedListBuilder<String, SimplePokemon>(dataSourceFactory, config)
    }

    fun pokemonPagedListLiveData(): LiveData<PagedList<SimplePokemon>> {
        return initializedPagedListBuilder(config).build()
    }
}

class PokemonAdapter :
    PagedListAdapter<SimplePokemon, PokemonAdapter.PokemonViewHolder>(PokemonDiffUtil()) {

    inner class PokemonViewHolder(v: View) : RecyclerView.ViewHolder(v) {
        private val pokemonNameTextView: TextView = v.findViewById(R.id.pokemon_name_text_view)
        private val pokemonFavoriteToggle: ToggleButton =
            v.findViewById(R.id.pokemon_favorite_toggle_button)

        fun bind(data: SimplePokemon) {
            pokemonNameTextView.text = data.name
            pokemonFavoriteToggle.isChecked = data.isFavorite
        }
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): PokemonViewHolder {
        val view =
            LayoutInflater.from(parent.context).inflate(R.layout.item_simple_pokemon, parent, false)
        return PokemonViewHolder(view)
    }

    override fun onBindViewHolder(holder: PokemonViewHolder, position: Int) {
        val item = getItem(position)
        item?.let { holder.bind(it) }
    }
}

class PokemonDataSource : PageKeyedDataSource<String, SimplePokemon>() {

    private val api = NetworkService.pokemonNetworkInterface

    override fun loadInitial(
        params: LoadInitialParams<String>,
        callback: LoadInitialCallback<String, SimplePokemon>
    ) {
        api.getPokemon().enqueue(object : Callback<PokeResponse<List<SimplePokemon>>> {

            override fun onFailure(call: Call<PokeResponse<List<SimplePokemon>>>?, t: Throwable?) {
                Log.e("PokemonDataSource", "Failed to fetch data!")
            }

            override fun onResponse(
                call: Call<PokeResponse<List<SimplePokemon>>>?,
                response: Response<PokeResponse<List<SimplePokemon>>>
            ) {
                val listing = response.body()
                val pokemon = listing?.results
                callback.onResult(pokemon ?: listOf(), listing?.previous, listing?.next)
            }
        })
    }

    override fun loadAfter(
        params: LoadParams<String>,
        callback: LoadCallback<String, SimplePokemon>
    ) {
        api.getPokemon(url = params.key)
            .enqueue(object : Callback<PokeResponse<List<SimplePokemon>>> {
                override fun onFailure(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    t: Throwable?
                ) {
                    Log.e("PokemonDataSource", "Failed to fetch data! Oh Noooo!")
                }

                override fun onResponse(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    response: Response<PokeResponse<List<SimplePokemon>>>
                ) {
                    val listing = response.body()
                    val pokemon = listing?.results
                    callback.onResult(pokemon ?: listOf(), listing?.next)
                }
            })
    }

    override fun loadBefore(
        params: LoadParams<String>,
        callback: LoadCallback<String, SimplePokemon>
    ) {
        api.getPokemon(url = params.key)
            .enqueue(object : Callback<PokeResponse<List<SimplePokemon>>> {
                override fun onFailure(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    t: Throwable?
                ) {
                    Log.e("PokemonDataSource", "Failed to fetch data! Oh Noooo!")
                }

                override fun onResponse(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    response: Response<PokeResponse<List<SimplePokemon>>>
                ) {
                    val listing = response.body()
                    val pokemon = listing?.results
                    callback.onResult(pokemon ?: listOf(), listing?.previous)
                }
            })
    }

class PokemonViewModel（应用程序：应用程序）：AndroidViewModel（应用程序）{
private val config=PagedList.config.Builder（）
.setPageSize（20）
.setEnablePlaceholders（false）
.build（）
private fun initializedPagedListBuilder（config:PagedList.config）：LivePagedListBuilder{
val dataSourceFactory=object:DataSource.Factory（）{
重写fun create（）：数据源{
return pokemondasource（）
}
}
返回LivePagedListBuilder（dataSourceFactory，配置）
}
fun pokemonPagedListLiveData（）：LiveData{
返回initializedPagedListBuilder（config）.build（）
}
}

PokemonAdapter.kt:

data class SimplePokemon(
    @SerializedName("name") val name: String,
    @SerializedName("url") val url: String,
    var isFavorite: Boolean = false
)

class PokemonViewModel(application: Application) : AndroidViewModel(application) {

    private val config = PagedList.Config.Builder()
        .setPageSize(20)
        .setEnablePlaceholders(false)
        .build()

    private fun initializedPagedListBuilder(config: PagedList.Config): LivePagedListBuilder<String, SimplePokemon> {
        val dataSourceFactory = object : DataSource.Factory<String, SimplePokemon>() {
            override fun create(): DataSource<String, SimplePokemon> {
                return PokemonDataSource()
            }
        }
        return LivePagedListBuilder<String, SimplePokemon>(dataSourceFactory, config)
    }

    fun pokemonPagedListLiveData(): LiveData<PagedList<SimplePokemon>> {
        return initializedPagedListBuilder(config).build()
    }
}

class PokemonAdapter :
    PagedListAdapter<SimplePokemon, PokemonAdapter.PokemonViewHolder>(PokemonDiffUtil()) {

    inner class PokemonViewHolder(v: View) : RecyclerView.ViewHolder(v) {
        private val pokemonNameTextView: TextView = v.findViewById(R.id.pokemon_name_text_view)
        private val pokemonFavoriteToggle: ToggleButton =
            v.findViewById(R.id.pokemon_favorite_toggle_button)

        fun bind(data: SimplePokemon) {
            pokemonNameTextView.text = data.name
            pokemonFavoriteToggle.isChecked = data.isFavorite
        }
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): PokemonViewHolder {
        val view =
            LayoutInflater.from(parent.context).inflate(R.layout.item_simple_pokemon, parent, false)
        return PokemonViewHolder(view)
    }

    override fun onBindViewHolder(holder: PokemonViewHolder, position: Int) {
        val item = getItem(position)
        item?.let { holder.bind(it) }
    }
}

class PokemonDataSource : PageKeyedDataSource<String, SimplePokemon>() {

    private val api = NetworkService.pokemonNetworkInterface

    override fun loadInitial(
        params: LoadInitialParams<String>,
        callback: LoadInitialCallback<String, SimplePokemon>
    ) {
        api.getPokemon().enqueue(object : Callback<PokeResponse<List<SimplePokemon>>> {

            override fun onFailure(call: Call<PokeResponse<List<SimplePokemon>>>?, t: Throwable?) {
                Log.e("PokemonDataSource", "Failed to fetch data!")
            }

            override fun onResponse(
                call: Call<PokeResponse<List<SimplePokemon>>>?,
                response: Response<PokeResponse<List<SimplePokemon>>>
            ) {
                val listing = response.body()
                val pokemon = listing?.results
                callback.onResult(pokemon ?: listOf(), listing?.previous, listing?.next)
            }
        })
    }

    override fun loadAfter(
        params: LoadParams<String>,
        callback: LoadCallback<String, SimplePokemon>
    ) {
        api.getPokemon(url = params.key)
            .enqueue(object : Callback<PokeResponse<List<SimplePokemon>>> {
                override fun onFailure(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    t: Throwable?
                ) {
                    Log.e("PokemonDataSource", "Failed to fetch data! Oh Noooo!")
                }

                override fun onResponse(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    response: Response<PokeResponse<List<SimplePokemon>>>
                ) {
                    val listing = response.body()
                    val pokemon = listing?.results
                    callback.onResult(pokemon ?: listOf(), listing?.next)
                }
            })
    }

    override fun loadBefore(
        params: LoadParams<String>,
        callback: LoadCallback<String, SimplePokemon>
    ) {
        api.getPokemon(url = params.key)
            .enqueue(object : Callback<PokeResponse<List<SimplePokemon>>> {
                override fun onFailure(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    t: Throwable?
                ) {
                    Log.e("PokemonDataSource", "Failed to fetch data! Oh Noooo!")
                }

                override fun onResponse(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    response: Response<PokeResponse<List<SimplePokemon>>>
                ) {
                    val listing = response.body()
                    val pokemon = listing?.results
                    callback.onResult(pokemon ?: listOf(), listing?.previous)
                }
            })
    }

class口袋妖怪：
PagedListAdapter（PokemonDiffUtil（））{
内部类PokemonViewHolder（v:View）：RecyclerView.ViewHolder（v）{
private val pokemonNameTextView:TextView=v.findViewById（R.id.pokemon\u name\u text\u视图）
private val PokemonFavoriteTokle:ToggleButton=
v、 findViewById（R.id.pokemon\u favorite\u toggle\u按钮）
趣味绑定（数据：SimplePokemon）{
pokemonNameTextView.text=data.name
PokemonFavoriteTokle.isChecked=data.isFavorite
}
}
override fun onCreateViewHolder（父级：ViewGroup，viewType:Int）：PokemonViewHolder{
瓦尔视图=
LayoutFlater.from（parent.context）.充气（R.layout.item\u simple\u pokemon，parent，false）
返回PokemonViewHolder（视图）
}
覆盖BindViewHolder（支架：PokemonViewHolder，位置：Int）{
val item=getItem（位置）
项目？让{holder.bind（it）}
}
}

pokemondasource.kt:

data class SimplePokemon(
    @SerializedName("name") val name: String,
    @SerializedName("url") val url: String,
    var isFavorite: Boolean = false
)

class PokemonViewModel(application: Application) : AndroidViewModel(application) {

    private val config = PagedList.Config.Builder()
        .setPageSize(20)
        .setEnablePlaceholders(false)
        .build()

    private fun initializedPagedListBuilder(config: PagedList.Config): LivePagedListBuilder<String, SimplePokemon> {
        val dataSourceFactory = object : DataSource.Factory<String, SimplePokemon>() {
            override fun create(): DataSource<String, SimplePokemon> {
                return PokemonDataSource()
            }
        }
        return LivePagedListBuilder<String, SimplePokemon>(dataSourceFactory, config)
    }

    fun pokemonPagedListLiveData(): LiveData<PagedList<SimplePokemon>> {
        return initializedPagedListBuilder(config).build()
    }
}

class PokemonAdapter :
    PagedListAdapter<SimplePokemon, PokemonAdapter.PokemonViewHolder>(PokemonDiffUtil()) {

    inner class PokemonViewHolder(v: View) : RecyclerView.ViewHolder(v) {
        private val pokemonNameTextView: TextView = v.findViewById(R.id.pokemon_name_text_view)
        private val pokemonFavoriteToggle: ToggleButton =
            v.findViewById(R.id.pokemon_favorite_toggle_button)

        fun bind(data: SimplePokemon) {
            pokemonNameTextView.text = data.name
            pokemonFavoriteToggle.isChecked = data.isFavorite
        }
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): PokemonViewHolder {
        val view =
            LayoutInflater.from(parent.context).inflate(R.layout.item_simple_pokemon, parent, false)
        return PokemonViewHolder(view)
    }

    override fun onBindViewHolder(holder: PokemonViewHolder, position: Int) {
        val item = getItem(position)
        item?.let { holder.bind(it) }
    }
}

class PokemonDataSource : PageKeyedDataSource<String, SimplePokemon>() {

    private val api = NetworkService.pokemonNetworkInterface

    override fun loadInitial(
        params: LoadInitialParams<String>,
        callback: LoadInitialCallback<String, SimplePokemon>
    ) {
        api.getPokemon().enqueue(object : Callback<PokeResponse<List<SimplePokemon>>> {

            override fun onFailure(call: Call<PokeResponse<List<SimplePokemon>>>?, t: Throwable?) {
                Log.e("PokemonDataSource", "Failed to fetch data!")
            }

            override fun onResponse(
                call: Call<PokeResponse<List<SimplePokemon>>>?,
                response: Response<PokeResponse<List<SimplePokemon>>>
            ) {
                val listing = response.body()
                val pokemon = listing?.results
                callback.onResult(pokemon ?: listOf(), listing?.previous, listing?.next)
            }
        })
    }

    override fun loadAfter(
        params: LoadParams<String>,
        callback: LoadCallback<String, SimplePokemon>
    ) {
        api.getPokemon(url = params.key)
            .enqueue(object : Callback<PokeResponse<List<SimplePokemon>>> {
                override fun onFailure(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    t: Throwable?
                ) {
                    Log.e("PokemonDataSource", "Failed to fetch data! Oh Noooo!")
                }

                override fun onResponse(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    response: Response<PokeResponse<List<SimplePokemon>>>
                ) {
                    val listing = response.body()
                    val pokemon = listing?.results
                    callback.onResult(pokemon ?: listOf(), listing?.next)
                }
            })
    }

    override fun loadBefore(
        params: LoadParams<String>,
        callback: LoadCallback<String, SimplePokemon>
    ) {
        api.getPokemon(url = params.key)
            .enqueue(object : Callback<PokeResponse<List<SimplePokemon>>> {
                override fun onFailure(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    t: Throwable?
                ) {
                    Log.e("PokemonDataSource", "Failed to fetch data! Oh Noooo!")
                }

                override fun onResponse(
                    call: Call<PokeResponse<List<SimplePokemon>>>?,
                    response: Response<PokeResponse<List<SimplePokemon>>>
                ) {
                    val listing = response.body()
                    val pokemon = listing?.results
                    callback.onResult(pokemon ?: listOf(), listing?.previous)
                }
            })
    }

class pokemondasource:PageKeyedDataSource（）{
private val api=NetworkService.pokemonNetworkInterface
覆盖趣味加载初始值(
params:LoadInitialParams，
回调：LoadInitialCallback
) {
api.getPokemon（）.enqueue（对象：回调{
覆盖失效时的乐趣（调用：调用？、t:可丢弃？）{
Log.e（“pokemondasource”，“无法获取数据！”）
}
覆盖响应(
呼叫：呼叫？，
答复：答复
) {
val listing=response.body（）
val pokemon=listing？.results
callback.onResult（pokemon？：listOf（），listing？.previous，listing？.next）
}
})
}
覆盖乐趣加载后(
参数：LoadParams，
回调：LoadCallback
) {
api.getPokemon（url=params.key）
.enqueue（对象：回调{
覆盖故障(
呼叫：呼叫？，
t:可以扔掉吗？
) {
Log.e（“pokemondasource”，“无法获取数据！噢，不！”
}
覆盖响应(
呼叫：呼叫？，
答复：答复
) {
val listing=response.body（）
val pokemon=listing？.results
callback.onResult（pokemon？：listOf（），listing？.next）
}
})
}
覆盖有趣的加载之前(
参数：LoadParams，
回调：LoadCallback
) {
api.getPokemon（url=params.key）
.enqueue（对象：回调{
覆盖故障(
呼叫：呼叫？，
t:可以扔掉吗？
) {
Log.e（“pokemondasource”，“无法获取数据！噢，不！”
}
覆盖响应(
呼叫：呼叫？，
答复：答复
) {
val listing=response.body（）
val pokemon=listing？.results
callback.onResult（口袋妖怪？：listOf（），listing？.previous）
}
})
}

我还想确保RecyclerView不会在每次更新数据源时跳转到顶部

理想的情况是，只要口袋妖怪活动还活着，就保留一个口袋妖怪列表，并能够在本地更新单个口袋妖怪项目。理论上，我也会向后端发送POST请求，以更新后端的口袋妖怪，但我只是想保留问题的答案