Android ViewPager2嵌套RecyclerView性能优化RecycledViewPool，kotlin

青旅半醒 2023-10-12 16:17 53阅读 0赞

## Android ViewPager2嵌套RecyclerView性能优化RecycledViewPool，kotlin ##

##  ##

<?xml version="1.0" encoding="utf-8"?>
    <androidx.viewpager2.widget.ViewPager2 xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/vp2"
        tools:context=".MainActivity">
    </androidx.viewpager2.widget.ViewPager2>

import android.os.Bundle
    import android.view.LayoutInflater
    import android.view.View
    import android.view.ViewGroup
    import android.widget.TextView
    import androidx.appcompat.app.AppCompatActivity
    import androidx.fragment.app.Fragment
    import androidx.fragment.app.FragmentActivity
    import androidx.recyclerview.widget.GridLayoutManager
    import androidx.recyclerview.widget.RecyclerView
    import androidx.recyclerview.widget.RecyclerView.RecycledViewPool
    import androidx.recyclerview.widget.RecyclerView.ViewHolder
    import androidx.viewpager2.adapter.FragmentStateAdapter
    import androidx.viewpager2.widget.ViewPager2
    
    
    class MainActivity : AppCompatActivity() {
        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
    
            val pager = findViewById<ViewPager2>(R.id.vp2)
            pager.adapter = MyPageAdapter(this)
    
            //如果是offscreenPageLimit=1，如果有三个Fragment（1,2,3），当前显示1，则第三个Fragment：3在不可见时候状态消失
            pager.offscreenPageLimit = 2
        }
    
        class MyPageAdapter(activity: FragmentActivity) : FragmentStateAdapter(activity) {
            var mRecycledViewPool = RecycledViewPool()
            var mFragments = arrayListOf<MyFragment>()
    
            init {
                mRecycledViewPool.setMaxRecycledViews(3, 500)
    
                for (i in 0 until 3) {
                    mFragments.add(MyFragment(i))
                }
            }
    
            override fun getItemCount(): Int {
                return mFragments.size
            }
    
            override fun createFragment(position: Int): Fragment {
                return mFragments[position]
            }
        }
    
        class MyFragment(private var seq: Int) : Fragment() {
            var mPool: RecycledViewPool? = null
    
            override fun onCreateView(
                inflater: LayoutInflater,
                container: ViewGroup?,
                savedInstanceState: Bundle?
            ): View? {
                var recyclerView = RecyclerView(inflater.context)
                var layoutManager = GridLayoutManager(inflater.context, 4)
                recyclerView.adapter = MyRecyclerViewAdapter(seq)
                recyclerView.layoutManager = layoutManager
    
    
                layoutManager.isItemPrefetchEnabled = true //Android源代码中默认true
                layoutManager.recycleChildrenOnDetach = true
                recyclerView.setRecycledViewPool(mPool)
                recyclerView.setHasFixedSize(true)
    
                return recyclerView
            }
        }
    
        class MyRecyclerViewAdapter(private var seq: Int) : RecyclerView.Adapter<MyVH>() {
            override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyVH {
                var view = LayoutInflater.from(parent.context)
                    .inflate(android.R.layout.simple_list_item_2, parent, false)
                return MyVH(view)
            }
    
            override fun getItemCount(): Int {
                return Int.MAX_VALUE
            }
    
            override fun onBindViewHolder(holder: MyVH, position: Int) {
                holder.text1.text = "F-$seq"
                holder.text2.text = "$position"
            }
        }
    
        class MyVH(itemView: View) : ViewHolder(itemView) {
            var text1: TextView
            var text2: TextView
    
            init {
                text1 = itemView.findViewById(android.R.id.text1)
                text2 = itemView.findViewById(android.R.id.text2)
            }
        }
    }

![9d601f97e31946d282bc6333fbc334c5.png][]

[ViewPager2和Fragment可见性及懒加载解决方案\_viewpager2 懒加载\_zhangphil的博客-CSDN博客ViewPager2和Fragment新的可见性及懒加载解决方案，旨在解决ViewPager（ViewPager2）只有当前Fragment唯一可见时候网络刷新或绘图。注意：过去的setUserVisibleHint()已被废弃，开发者不要再使用基于setUserVisibleHint()解决Fragment可见性和懒加载（或延迟加载）的场景。新方案用最新的ViewPager2替代过去旧版的ViewPager，再结合Fragment的resume和pause生命周期实现。写一个demo例子，测试的主类M![favicon32.ico][]https://blog.csdn.net/zhangphil/article/details/108893237][ViewPager2_Fragment_viewpager2 _zhangphil_-CSDN_ViewPager2_Fragment_ViewPager_ViewPager2_Fragment_setUserVisibleHint_setUserVisibleHint_Fragment_ViewPager2_ViewPager_Fragment_resume_pause_demo_M_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_108893237]

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[ViewPager2_Fragment_viewpager2 _zhangphil_-CSDN_ViewPager2_Fragment_ViewPager_ViewPager2_Fragment_setUserVisibleHint_setUserVisibleHint_Fragment_ViewPager2_ViewPager_Fragment_resume_pause_demo_M_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_108893237]: https://blog.csdn.net/zhangphil/article/details/108893237