手把手教你搭建android模块化项目框架（八）小试牛刀——带搜索列表的页面 paging,mvvm及flow的运用

@Entity(primaryKeys = ["number", "lotteryType", "remoteName"])
data class LotteryEntity(
    val lotteryType: String,
    val numbers: MutableList<String>,
    val dateTime: String,
    val number: String,
    val remoteName: String
)

@Dao
interface LotteryDao {
    @Query("SELECT * FROM LotteryEntity WHERE remoteName = :remoteName ORDER BY number desc")
    fun getLotteryPagingSource(
        remoteName: String
    ): PagingSource<Int, LotteryEntity>

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    suspend fun insertAllAsync(mList: List<LotteryEntity>)

    @Query("DELETE FROM LotteryEntity WHERE remoteName = :remoteName")
    suspend fun clearLocalDataByRemoteNameAsync(remoteName: String)
}

class LotteryMediator(private val queryStr: String) :
    BaseRemoteMediator<LotteryEntity, LotteryModel>("LotteryMediator") {
    override suspend fun load(
        loadKey: String,
        loadType: LoadType,
        pageConfig: PagingConfig
    ): Boolean {
        //由于没有后台支持，这里我的数据全是静态页，因此搜索条件最终也拼成了url地址。
        //本文提供的是一个思路，这里把queryStr当成参数就可以了

        val repo = repo {
            api { loadKey.ifBlank { queryStr } }
        }

        val result = repo.request<LotteryList>()

        val lotteryEntities = result.data.map {
            it.toLotteryEntity(remoteName)
        }
        RoomDB.INSTANCE.withTransaction {
            if (loadType == LoadType.REFRESH) {
                //拿到结果后，如果判断出是刷新，先清空数据库
                clearLocalData()
            }
            LotteryDB.insertAll(lotteryEntities)
            RemoteDB.insertAsync(RemoteEntity(remoteName, result.next))
        }
        return result.next.isBlank()
    }

    override suspend fun clearLocalData() {
        //LotteryDB为数据库查询类，之前讲room的章节有提到过。
        LotteryDB.clearLocalDataByRemoteNameAsync(remoteName)
    }
}

class LotteriesAct : BaseBindingAct<LotteriedActBinding>() {
    override val mBinding by binding<LotteriedActBinding>(R.layout.lotteried_act)
    private val mViewModel by viewModels<LotteriesViewModel>()
    override fun setupView() {
        super.setupView()
        setupRv()
        setupSearch()
    }

    override fun variables(): SparseArray<ViewModel> {
        return sparse(BR.lotteryVM to mViewModel)
    }

    override fun setupData() {
        super.setupData()
        fetchData()
    }

    private val adapter by lazy { LotteryAdapter() }

    @OptIn(FlowPreview::class)
    private fun setupSearch() {
        mBinding.search
            .toFlow()
            .debounce(1000)
            .distinctUntilChangedBy {
                mViewModel.searchObs.value = it.toString()
            }.launchIn(lifecycleScope).start()
    }

    private fun setupRv() {
        mBinding.swipeRl.setOnRefreshListener {
            adapter.refresh()
        }
        val concatAdapter = adapter.concat(
            VerticalFooterAdapter(adapter),
            EmptyAdapter(adapter, LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT)
        )
        mBinding.rv.layoutManager = LinearLayoutManager(this)
        mBinding.rv.adapter = concatAdapter
        adapter.setup(lifecycleScope, mBinding.rv) {
            mViewModel.loadingObs.value = it.mediator?.refresh == LoadState.Loading
        }
    }

    private fun fetchData() {
        lifecycleScope.launch {
            mViewModel.posts.collectLatest {
                adapter.submitData(it)
            }
        }
    }
}

class LotteriesViewModel : BaseViewModel() {
    val loadingObs = MutableLiveData(false)
    val searchObs = MutableLiveData("")

    @OptIn(ExperimentalCoroutinesApi::class)
    val posts = searchObs.asFlow()
        .flatMapLatest {
            //由于没有服务器支持，所以这里将输入文本框的其实是页码数，这里当作正常的query条件看就可以啦~
            val page = it.ifBlank { "1" }
            val api = "https://liyuzheng.github.io/bigfile.io/lottery/shuangseqiu$page.html"
            fetch(api)
        }.cachedIn(viewModelScope)


    suspend fun fetch(queryStr: String) = LotteryListRepo.getPagingFlow(this, queryStr)
}

@BindingAdapter("bindLoadState")
fun bindLoadState(view: SwipeRefreshLayout, loading: Boolean?) {
    view.isRefreshing = loading == true
}

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:bind="http://schemas.android.com/apk/res-auto">

    <data>

        <variable
            name="lotteryVM"
            type="yz.l.feature_lottery.LotteriesViewModel" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <EditText
            android:id="@+id/search"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:paddingHorizontal="16dp"
            android:textSize="16sp"
            android:enabled="@{lotteryVM.loadingObs != true}"
            bind:layout_constraintTop_toTopOf="parent" />

        <androidx.swiperefreshlayout.widget.SwipeRefreshLayout
            android:id="@+id/swipe_rl"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            bind:bindLoadState="@{lotteryVM.loadingObs}"
            bind:layout_constraintBottom_toBottomOf="parent"
            bind:layout_constraintTop_toBottomOf="@id/search">

            <androidx.recyclerview.widget.RecyclerView
                android:id="@+id/rv"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                bind:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"/>
        </androidx.swiperefreshlayout.widget.SwipeRefreshLayout>
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>