ViewPager 不膨胀片段

Question

我正在使用ViewPager2、FragmentStateAdapter 和TabLayout 创建选项卡式布局。我的 TabLayout 和 ViewPager2 在 Fragment 中，并且适配器有一个列表，其中包含另外两个用于选项卡的片段。当我使用调试器或在日志语句中时，永远不会调用每个片段的 OnCreateView。 createFragment 也永远不会在选项卡适配器中调用

MainTabHolderFragment：片段

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    val tabAdapter = TabAdapter(childFragmentManager, lifecycle)
    tabAdapter.addFragment(AddItemFragment(), "Add Item")
    tabAdapter.addFragment(WishListFragment(), "Wish List")

    binding.viewPager.adapter = tabAdapter
    TabLayoutMediator(
        binding.tabLayout, binding.viewPager,
        TabLayoutMediator.TabConfigurationStrategy { tab, position ->
            tab.text = tabAdapter.getPageTitle(position)
            Timber.d("tab = ${tab.position}, pos = $position")
            binding.viewPager.setCurrentItem(position, true)
        }).attach()
}

TabAdapter

class TabAdapter(fm: FragmentManager, lifecycle: Lifecycle) : FragmentStateAdapter(fm, lifecycle) {

    private val fragmentList = mutableListOf<FragmentListItem>()

    override fun createFragment(position: Int) = fragmentList[position].fragment

    override fun getItemCount() = fragmentList.size

    fun addFragment(fragment: Fragment, title: String) {
        fragmentList.add(FragmentListItem(fragment, title))
    }

    fun getPageTitle(position: Int): CharSequence? = fragmentList[position].title


    private data class FragmentListItem(val fragment: Fragment, val title: String)
}

TabLayoutMediator 中的tab.postion 变量始终为-1，ViewPager 永远不会对fragment 进行膨胀，导致tab 布局下出现黑屏。我需要使用TabLayoutMediator 或FragmentStateAdapter 以外的其他内容吗？

编辑：添加了说明 createFragment 未调用的信息

Answer 1

太简单了，添加这个..（ONCREATEVIEW 内部）

TabLayout tabs = (TabLayout) findViewById(R.id.tabsID);

    tabsID.addTab(tabsID.newTab().setText("Fragment1"));
    tabsID.addTab(tabsID.newTab().setText("Fragment2"));

现在您已经有了带有名称的 tablayout，现在创建方法（ONCREATEVIEW 之外），您必须为每个 TABITEM 创建一个

public void homeScreen () {
    homeAdapter = new ArrayAdapter<String>(getActivity(),android.R.layout.simple_list_item_activated_2, homeInformation) {
        @NonNull
        @Override
        public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
            if (convertView == null) {
                LayoutInflater inflater = (LayoutInflater) getActivity().getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                convertView = inflater.inflate(R.layout.home_item, parent, false);
            }

            Random rand = new Random();
            int random_number_home = rand.nextInt(10) + 1;

            TextView number_home_list  = (TextView) convertView.findViewById(R.id.number_home_list);
            TextView textViewHome = (TextView) convertView.findViewById(R.id.textViewHome);
            textViewHome.setText(homeInformation[position]);
            number_home_list.setText(Integer.toString(random_number_home));
            return convertView;
        }
    };
    homeList.setAdapter(homeAdapter);
}

此代码显示带有随机数的列表视图，现在此代码用于选择不同的选项卡....当您进入应用程序时，第一个主屏幕是您看到的第一个主屏幕（ONCREATEVIEW 内部）

homeScreen();

    final TabLayout.BaseOnTabSelectedListener eventChangeTab = new TabLayout.BaseOnTabSelectedListener() {
        @Override
        public void onTabSelected(TabLayout.Tab tab) {
            if (tab.getText().toString().equals("Resumen")) {
                homeScreen();
            } else if (tab.getText().toString().equals("Datos Abonado")) {
                receiptsScreen();
            } 
        }


        @Override
        public void onTabUnselected(TabLayout.Tab tab) {

        }


        @Override
        public void onTabReselected(TabLayout.Tab tab) {
            if (tab.getText().toString().equals("Fragment1")) {
                homeScreen();
            } else if (tab.getText().toString().equals("Fragment2")) {
                receiptsScreen();
            } 
        }
    };

    tabsID.addOnTabSelectedListener(eventChangeTab );

Answer 2

我的建议是仅使用 Fragment 参数更改 TabAdapterConstructor，并将其用作我个人项目的下一个方法：

class YourAdapter(fragment: Fragment) : FragmentStateAdapter(fragment) {

    private lateinit var yourList: List<YourListType>

    override fun getItemCount(): Int = yourList.size

    override fun createFragment(position: Int): Fragment =
        YourFragment.instance(yourList[position]) // Only is needed to pass data

    fun setList(yourList: List<YourListType>) {
        this.yourList = yourList
    }
} 

以及在主片段中设置的ViewPager：

view_pager.adapter = YourAdapter(this).apply{ 
    setList(yourList) 
}

以及初始化Fragment的方法：

companion object {
        private const val KEY_YOUR_OBJECT = "KEY_YOUR_OBJECT"

        fun instance(yourObject: YourObject): YourFragment {
            val arguments = Bundle().apply {
                putSerializable(KEY_YOUR_OBJECT, yourObject)
            }

            return YourFragment().apply {
                this.arguments = arguments
            }
        }
}