viewpage2本身自带了懒加载模式，十分人性化。
class TabLayoutActivity : AppCompatActivity() {private lateinit var mPagerAdapter: TabPagerAdapteroverride fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)setContentView(R.layout.activity_tablayout)mPagerAdapter = TabPagerAdapter(this)initTab()// initOther()}private fun initOther(){val joinStr1 = arrayOf("a","b","c","d").joinToString(separator = "",prefix = "前缀",postfix = "后缀",limit = 3,truncated = "····").apply {print(this)}}private fun initTab() {val titles = arrayListOf("精选","体育","巴萨","购物","明星","视频","健康","励志","图文","本地","动漫","搞笑","舞蹈","其他")val fragments = ArrayList<Fragment>()titles.indices.map { i->fragments.add(TestFragment())}mPagerAdapter.setNewFragments(fragments)viewpager.orientation = ViewPager2.ORIENTATION_HORIZONTALviewpager.adapter = mPagerAdapterTabLayoutMediator(tabs, viewpager,TabLayoutMediator.TabConfigurationStrategy { tab, position -> tab.text = titles[position] }).attach()viewpager.registerOnPageChangeCallback(object :ViewPager2.OnPageChangeCallback(){})}
class TestFragment : Fragment() {override fun onCreateView(inflater: LayoutInflater,container: ViewGroup?,savedInstanceState: Bundle?): View? {return inflater.inflate(R.layout.fragment_item_one, container, false)}override fun onViewCreated(view: View, savedInstanceState: Bundle?) {super.onViewCreated(view, savedInstanceState)tv_item.text = javaClass.nametv_item.background = ContextCompat.getDrawable(requireContext(), R.mipmap.bianpao)}}
class TabPagerAdapter(fragmentActivity: FragmentActivity) : FragmentStateAdapter(fragmentActivity) {private val mFragmentList = ArrayList<Fragment>()fun setNewFragments(data: ArrayList<Fragment>) {if (data.isNotEmpty()) {mFragmentList.clear()mFragmentList.addAll(data)notifyDataSetChanged()}}fun removeFragment(position: Int) {if (mFragmentList.size > position) {mFragmentList.remove(mFragmentList[position])notifyDataSetChanged()}}override fun getItemCount(): Int {return mFragmentList.size}override fun createFragment(position: Int): Fragment {return mFragmentList[position]}}
