ViewPager2无法动态添加删除片段 [英] ViewPager2 not able to dynamically add remove fragment

问题描述

在索引处删除/添加片段会导致Viewpager2中出现意外行为.对于ViewPager，这是不可能的，但希望与Viewpager2一起工作.这会导致重复的片段并且不同步TabLayout. 这是一个演示项目，它再现了此问题.有一个切换按钮，可删除片段并将其重新连接到特定索引.在这种情况下，附加的片段应为绿色，但应为蓝色，并且以某种方式有2个蓝色片段.

Removing/Adding fragments at index results in unexpected behaviour in Viewpager2. This was not possible with ViewPager but expected to work with Viewpager2. It causes duplicate fragments and out of sync TabLayout. Here is a demo project which reproduces this issue. There is a toggle button which removes a fragment and reattaches it at a particular index. In this case attached fragment should be green but it's blue and there are 2 blue fragments somehow.

这是我的适配器的外观

class ViewPager2Adapter(activity: FragmentActivity) : FragmentStateAdapter(activity) {
    val fragmentList: MutableList<FragmentName> = mutableListOf()

    override fun getItemCount(): Int {
        return fragmentList.size
    }

    override fun createFragment(position: Int): Fragment {
        return when (fragmentList[position]) {
            FragmentName.WHITE -> WhiteFragment()
            FragmentName.RED -> RedFragment()
            FragmentName.GREEN -> GreenFragment()
            FragmentName.BLUE -> BlueFragment()
        }
    }

    fun add(fragment: FragmentName) {
        fragmentList.add(fragment)
        notifyDataSetChanged()
    }

    fun add(index: Int, fragment: FragmentName) {
        fragmentList.add(index, fragment)
        notifyDataSetChanged()
    }

    fun remove(index: Int) {
        fragmentList.removeAt(index)
        notifyDataSetChanged()
    }

    fun remove(name: FragmentName) {
        fragmentList.remove(name)
        notifyDataSetChanged()
    }

    enum class FragmentName {
        WHITE,
        RED,
        GREEN,
        BLUE
    }
}

我也已经向Google提交了 bug

I have filed a bug with google as well

推荐答案

如果在ViewPager2

override fun getItemId(position: Int): Long {
        return fragmentList[position].ordinal.toLong()
    }

    override fun containsItem(itemId: Long): Boolean {
        val fragment = FragmentName.values()[itemId.toInt()]
        return fragmentList.contains(fragment)
    }

将这两个添加到当前适配器中可以解决此问题

Adding these two in my current adapter fixes the problem

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