안드로이드 ViewPager2 + Fragment swipe

ViewPager2를 사용해 fragement swape를 구현해 봤다.

핵심은 ViewPager2에 FragmentStateAdapter를 구현하는 것이다.

 

PageAdapter.kt

package com.example.myviewpager2fragment.adapter

import androidx.fragment.app.Fragment
import androidx.fragment.app.FragmentActivity
import androidx.viewpager2.adapter.FragmentStateAdapter

class PageAdapter(fragmentActivity: FragmentActivity, fragments: List<Fragment>) :
    FragmentStateAdapter(fragmentActivity) {

    private val fragmentList = mutableListOf<Fragment>()

    init {
        fragmentList.addAll(fragments)
    }

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

    override fun createFragment(position: Int): Fragment {
        return fragmentList[position]
    }
}

MainActivity.kt

package com.example.myviewpager2fragment

import android.os.Bundle
import android.os.Handler
import android.os.Looper
import android.util.Log
import android.view.View
import androidx.activity.OnBackPressedCallback
import androidx.activity.enableEdgeToEdge
import androidx.appcompat.app.AppCompatActivity
import androidx.core.view.ViewCompat
import androidx.core.view.WindowInsetsCompat
import androidx.fragment.app.Fragment
import androidx.viewpager2.widget.ViewPager2.OnPageChangeCallback
import com.example.myviewpager2fragment.adapter.PageAdapter
import com.example.myviewpager2fragment.databinding.ActivityMainBinding
import com.example.myviewpager2fragment.fragment.FirstFragment
import com.example.myviewpager2fragment.fragment.SecondFragment
import kotlin.system.exitProcess

class MainActivity : AppCompatActivity() {

    private val binding by lazy {
        ActivityMainBinding.inflate(layoutInflater)
    }
    private lateinit var pageAdapter: PageAdapter
    private lateinit var fragmentList: MutableList<Fragment>
    private lateinit var firstFragment: FirstFragment
    private lateinit var secondFragment: SecondFragment

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        enableEdgeToEdge()
        setContentView(binding.root)
        ViewCompat.setOnApplyWindowInsetsListener(binding.main) { v, insets ->
            val systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars())
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom)
            insets
        }

        this.onBackPressedDispatcher.addCallback(this,object:OnBackPressedCallback(true){
            override fun handleOnBackPressed() {
                if(binding.activityMainViewPager2.currentItem==0) {
                    Handler(mainLooper).postDelayed({
                        finishAndRemoveTask()
                        exitProcess(0)
                    },100)
                } else {
                    binding.activityMainViewPager2.currentItem -= 1
                }
            }
        })

        firstFragment = FirstFragment(binding)
        secondFragment = SecondFragment()
        fragmentList = mutableListOf(firstFragment, secondFragment)

        pageAdapter = PageAdapter(this, fragmentList)

        with(binding) {
            activityMainViewPager2.apply {
                adapter = pageAdapter
                registerOnPageChangeCallback(object : OnPageChangeCallback() {
                    override fun onPageSelected(position: Int) {
                        super.onPageSelected(position)
                        activityMainImageButtonBack.visibility =
                            if (position == 0) View.INVISIBLE else View.VISIBLE
                    }
                })
            }
            activityMainImageButtonBack.setOnClickListener {
                if (activityMainViewPager2.currentItem == 1) {
                    activityMainViewPager2.currentItem = 0
                }
            }
        }
    }
}