ViewPager2

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1. class MainActivity : AppCompatActivity() {  
2.   
3.     private val binding by lazy { ActivityMainBinding.inflate(layoutInflater) }  
4.   
5.     override fun onCreate(savedInstanceState: Bundle?) {  
6.         super.onCreate(savedInstanceState)  
7.         setContentView(binding.root)  
8.   
9.         val adapter = PagerAdapter(this)  
10.         binding.pager.adapter = adapter  
11.   
12.         // MDC の TabLayout と組み合わせるときは TabLayoutMediator を使う  
13.         // TabLayoutMediator の attach は ViewPager2 に adapter をセットした後に行う  
14.         TabLayoutMediator(binding.tabLayout, binding.pager) { tab, position ->  
15.             tab.text = adapter.getTitle(position)  
16.         }.attach()  
17.     }  
18. }  
19.   
20. private class PagerAdapter(  
21.     fragmentActivity: FragmentActivity  
22. ) : FragmentStateAdapter(fragmentActivity) {  
23.   
24.     override fun getItemCount(): Int {  
25.         return ...  
26.     }  
27.   
28.     override fun createFragment(position: Int): Fragment {  
29.         return PageFragment.newInstance(...)  
30.     }  
31.   
32.     fun getTitle(position: Int): String {  
33.         return ...  
34.     }  
35. }  

class MainActivity : AppCompatActivity() { private val binding by lazy { ActivityMainBinding.inflate(layoutInflater) } override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(binding.root) val adapter = PagerAdapter(this) binding.pager.adapter = adapter // MDC の TabLayout と組み合わせるときは TabLayoutMediator を使う // TabLayoutMediator の attach は ViewPager2 に adapter をセットした後に行う TabLayoutMediator(binding.tabLayout, binding.pager) { tab, position -> tab.text = adapter.getTitle(position) }.attach() } } private class PagerAdapter( fragmentActivity: FragmentActivity ) : FragmentStateAdapter(fragmentActivity) { override fun getItemCount(): Int { return ... } override fun createFragment(position: Int): Fragment { return PageFragment.newInstance(...) } fun getTitle(position: Int): String { return ... } }