Android Paging3/Page3 Cursor query segment photo into 3 grid RecyclerView,kotlin （2）

怼烎@ 2023-09-27 23:33 23阅读 0赞

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
        <uses-permission android:name="android.permission.READ_MEDIA_IMAGES" />

def paging_version = "3.1.1"
        implementation "androidx.paging:paging-runtime:$paging_version"
        implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.4.0'
        implementation 'com.github.bumptech.glide:glide:4.15.1'

import androidx.appcompat.app.AppCompatActivity
    import android.os.Bundle
    import android.util.Log
    import androidx.lifecycle.ViewModel
    import androidx.lifecycle.ViewModelProvider
    import androidx.lifecycle.asLiveData
    import androidx.lifecycle.get
    import androidx.lifecycle.viewModelScope
    import androidx.paging.LoadState
    import androidx.paging.cachedIn
    import androidx.recyclerview.widget.GridLayoutManager
    import androidx.recyclerview.widget.RecyclerView
    
    
    class MainActivity : AppCompatActivity() {
        companion object {
            val TAG = "paging-test"
        }
    
        private val viewModel by lazy { ViewModelProvider(this).get<MainViewModel>() }
        private val myAdapter = MyAdapter()
    
        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
            val recyclerView = findViewById<RecyclerView>(R.id.recycler_view)
            recyclerView.layoutManager = GridLayoutManager(this, 3).apply {
                orientation = GridLayoutManager.VERTICAL
            }
    
            recyclerView.adapter = myAdapter
    
            val liveData =
                MyDataFlow.getPagingData(this).cachedIn(viewModel.viewModelScope).asLiveData()
            liveData.observe(this) {
                myAdapter.submitData(lifecycle, it)
            }
    
            myAdapter.addLoadStateListener {
                when (it.refresh) {
                    is LoadState.NotLoading -> {
                        //recyclerView.visibility = View.VISIBLE
                        Log.d(TAG, "LoadState.NotLoading")
                    }
    
                    is LoadState.Loading -> {
                        //recyclerView.visibility = View.INVISIBLE
                        Log.d(TAG, "LoadState.Loading")
                    }
    
                    is LoadState.Error -> {
                        val state = it.refresh as LoadState.Error
                        Log.d(TAG, "LoadState.Error")
                    }
                }
            }
        }
    
        class MainViewModel : ViewModel() {
    
        }
    }

<?xml version="1.0" encoding="utf-8"?>
    <androidx.recyclerview.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity" />

import android.view.LayoutInflater
    import android.view.View
    import android.view.ViewGroup
    import android.widget.ImageView
    import android.widget.TextView
    import androidx.paging.PagingDataAdapter
    import androidx.recyclerview.widget.DiffUtil
    import androidx.recyclerview.widget.RecyclerView
    import com.bumptech.glide.Glide
    
    class MyAdapter : PagingDataAdapter<MyData, MyAdapter.ViewHolder>(COMPARATOR) {
        companion object {
            private val COMPARATOR = object : DiffUtil.ItemCallback<MyData>() {
                override fun areItemsTheSame(oldItem: MyData, newItem: MyData): Boolean {
                    return oldItem.id == newItem.id
                }
    
                override fun areContentsTheSame(oldItem: MyData, newItem: MyData): Boolean {
                    return oldItem == newItem
                }
            }
        }
    
        class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
            val page: TextView = itemView.findViewById(R.id.page)
            val in_page_pos: TextView = itemView.findViewById(R.id.in_page_pos)
            val image: ImageView = itemView.findViewById(R.id.image)
        }
    
        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
            val view = LayoutInflater.from(parent.context).inflate(R.layout.item, parent, false)
            return ViewHolder(view)
        }
    
        override fun onBindViewHolder(holder: ViewHolder, position: Int) {
            val data = getItem(position)
            if (data != null) {
                holder.page.text = "page=${data.page}"
                holder.in_page_pos.text = "${data.inPagePos}/${data.pageSize}"
                Glide.with(holder.itemView.context).load(data.path).into(holder.image)
            }
        }
    }

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="130dp"
        android:orientation="vertical"
        android:padding="1dp">
    
        <ImageView
            android:id="@+id/image"
            android:layout_width="match_parent"
            android:layout_height="80dp"
            android:scaleType="centerCrop"
            android:src="@mipmap/ic_launcher" />
    
        <TextView
            android:id="@+id/page"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:text="0" />
    
        <TextView
            android:id="@+id/in_page_pos"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:text="0/0" />
    
    </LinearLayout>

import java.util.UUID
    
    data class MyData(
        val id: UUID,
        val page: Int,
        val inPagePos: Int,
        val pageSize: Int,
        val path: String?
    )

import android.content.Context
    import androidx.paging.Pager
    import androidx.paging.PagingConfig
    import androidx.paging.PagingData
    import kotlinx.coroutines.flow.Flow
    
    object MyDataFlow {
        const val PAGE_SIZE = 5
        const val INIT_LOAD_SIZE = PAGE_SIZE
    
        private val myLoadDataService = MyLoadDataService.create()
    
        fun getPagingData(ctx: Context): Flow<PagingData<MyData>> {
            return Pager(
                config = PagingConfig(
                    initialLoadSize = INIT_LOAD_SIZE, //程序启动第1次load的第1页数据的数量，不是页数
                    pageSize = PAGE_SIZE, //每一次分页加载的数量，不是页数
                    prefetchDistance =PAGE_SIZE * 2, //距离底部多少条时候启动预加载，若做到用户滑动无感知，可以将此值设置的大些，比如PAGE_SIZE的n倍。
                    enablePlaceholders = true,
                    maxSize = Int.MAX_VALUE
                ),
                pagingSourceFactory = { MyPagingDataSource(ctx, myLoadDataService) }
            ).flow
        }
    }

import android.content.Context
    import android.database.Cursor
    import android.provider.MediaStore
    import android.util.Log
    import java.util.UUID
    
    class MyLoadDataService {
        suspend fun loadData(ctx: Context, page: Int, perPage: Int): ArrayList<MyData> {
            Log.d(MainActivity.TAG, "-> $page - $perPage")
    
            val cursor: Cursor? = ctx.contentResolver.query(
                MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
                null,
                null,
                null,
                null
            )
            Log.d(MainActivity.TAG, "总数=${cursor?.count}")
    
            cursor?.moveToNext()
    
            cursor?.moveToPosition((page - 1) * perPage)
            Log.d(MainActivity.TAG, "cursor move to position = ${cursor?.position}")
    
            Log.d(MainActivity.TAG, "moveToNext start $page - $perPage")
            val items: ArrayList<MyData> = ArrayList()
            for (i in 1..perPage) {
                //图片的路径
                val path = cursor?.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA))
                val myData = MyData(UUID.randomUUID(), page, i, perPage, path)
    
                items.add(myData)
    
                cursor?.moveToNext()
            }
            Log.d(MainActivity.TAG, "moveToNext end $page - $perPage")
    
            cursor?.close()
    
            Log.d(MainActivity.TAG, "<- $page - $perPage")
    
            return items
        }
    
        companion object {
            fun create(): MyLoadDataService {
                return MyLoadDataService()
            }
        }
    }

import android.content.Context
    import androidx.paging.PagingSource
    import androidx.paging.PagingState
    
    class MyPagingDataSource(
        private val ctx: Context,
        private val myLoadDataService: MyLoadDataService
    ) :
        PagingSource<Int, MyData>() {
    
        override suspend fun load(params: LoadParams<Int>): LoadResult<Int, MyData> {
            return try {
                val page = params.key ?: 1 // set page 1 as default
                val pageSize = params.loadSize
    
                var items: ArrayList<MyData> = myLoadDataService.loadData(ctx, page, pageSize)
    
                val prevKey = if (page > 1) page - 1 else null
                val nextKey = if (items.isNotEmpty()) page + 1 else null
                LoadResult.Page(items, prevKey, nextKey)
            } catch (e: Exception) {
                LoadResult.Error(e)
            }
        }
    
        override fun getRefreshKey(state: PagingState<Int, MyData>): Int? {
            return 0
        }
    }

[Android Paging 3 Flow or LiveData,kotlin（1）\_zhangphil的博客-CSDN博客【代码】Android Paging 3,kotlin（1）![favicon32.ico][]https://blog.csdn.net/zhangphil/article/details/130735753][Android Paging 3 Flow or LiveData_kotlin_1_zhangphil_-CSDN_Android Paging 3_kotlin_1_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_130735753]

[基于Android官方Paging Library的RecyclerView分页加载框架\_android setmainthreadexecutor\_zhangphil的博客-CSDN博客基于Android官方Paging Library的RecyclerView分页加载框架我之前写了一篇RecyclerView分页加载机制的文章，是基于Android官方的AsyncListUtil实现的，详情见附录文章1。现在再介绍一种RecyclerView分页加载框架：Android Paging Library。Android Paging Library是Android官方support![favicon32.ico][]https://blog.csdn.net/zhangphil/article/details/78627332][Android_Paging Library_RecyclerView_android setmainthreadexecutor_zhangphil_-CSDN_Android_Paging Library_RecyclerView_RecyclerView_Android_AsyncListUtil_1_RecyclerView_Android Paging Library_Android Paging Library_Android_support_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_78627332]

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