viewPager

app/src/main/java/io/legado/app/ui/main/MainActivity.kt

@@ -3,10 +3,12 @@ package io.legado.app.ui.main
 import android.os.Bundle
 import android.view.KeyEvent
 import android.view.MenuItem
+import android.view.ViewGroup
 import androidx.activity.viewModels
 import androidx.fragment.app.Fragment
-import androidx.viewpager2.adapter.FragmentStateAdapter
+import androidx.fragment.app.FragmentManager
-import androidx.viewpager2.widget.ViewPager2
+import androidx.fragment.app.FragmentStatePagerAdapter
+import androidx.viewpager.widget.ViewPager
 import com.google.android.material.bottomnavigation.BottomNavigationView
 import io.legado.app.BuildConfig
 import io.legado.app.R
@@ -34,15 +36,14 @@ import io.legado.app.utils.toastOnUi
 
 class MainActivity : VMBaseActivity<ActivityMainBinding, MainViewModel>(),
     BottomNavigationView.OnNavigationItemSelectedListener,
-    BottomNavigationView.OnNavigationItemReselectedListener {
+    BottomNavigationView.OnNavigationItemReselectedListener,
+    ViewPager.OnPageChangeListener by ViewPager.SimpleOnPageChangeListener() {
     override val viewModel: MainViewModel by viewModels()
     private var exitTime: Long = 0
     private var bookshelfReselected: Long = 0
     private var exploreReselected: Long = 0
     private var pagePosition = 0
-    private val fragmentMap = hashMapOf<Long, Fragment>()
+    private val fragmentMap = hashMapOf<Int, Fragment>()
-
-    val viewPager get() = binding.viewPagerMain
 
     override fun getViewBinding(): ActivityMainBinding {
         return ActivityMainBinding.inflate(layoutInflater)
@@ -52,21 +53,8 @@ class MainActivity : VMBaseActivity<ActivityMainBinding, MainViewModel>(),
         ATH.applyEdgeEffectColor(viewPagerMain)
         ATH.applyBottomNavigationColor(bottomNavigationView)
         viewPagerMain.offscreenPageLimit = 3
-        viewPagerMain.adapter = TabFragmentPageAdapter()
+        viewPagerMain.adapter = TabFragmentPageAdapter(supportFragmentManager)
-        viewPagerMain.registerOnPageChangeCallback(object : ViewPager2.OnPageChangeCallback() {
+        viewPagerMain.addOnPageChangeListener(this@MainActivity)
-            override fun onPageSelected(position: Int) {
-                viewPagerMain.isUserInputEnabled = (viewPagerMain.currentItem != 0)
-                pagePosition = position
-                when (position) {
-                    0, 1, 3 -> bottomNavigationView.menu.getItem(position).isChecked = true
-                    2 -> if (AppConfig.isShowRSS) {
-                        bottomNavigationView.menu.getItem(position).isChecked = true
-                    } else {
-                        bottomNavigationView.menu.getItem(3).isChecked = true
-                    }
-                }
-            }
-        })
         bottomNavigationView.elevation =
             if (AppConfig.elevation < 0) elevation else AppConfig.elevation.toFloat()
         bottomNavigationView.setOnNavigationItemSelectedListener(this@MainActivity)
@@ -104,14 +92,14 @@ class MainActivity : VMBaseActivity<ActivityMainBinding, MainViewModel>(),
                 if (System.currentTimeMillis() - bookshelfReselected > 300) {
                     bookshelfReselected = System.currentTimeMillis()
                 } else {
-                    (fragmentMap[0L] as? BookshelfFragment)?.gotoTop()
+                    (fragmentMap[0] as? BookshelfFragment)?.gotoTop()
                 }
             }
             R.id.menu_explore -> {
                 if (System.currentTimeMillis() - exploreReselected > 300) {
                     exploreReselected = System.currentTimeMillis()
                 } else {
-                    (fragmentMap[1L] as? ExploreFragment)?.compressExplore()
+                    (fragmentMap[1] as? ExploreFragment)?.compressExplore()
                 }
             }
         }
@@ -132,6 +120,18 @@ class MainActivity : VMBaseActivity<ActivityMainBinding, MainViewModel>(),
         }
     }
 
+    override fun onPageSelected(position: Int) = with(binding) {
+        pagePosition = position
+        when (position) {
+            0, 1, 3 -> bottomNavigationView.menu.getItem(position).isChecked = true
+            2 -> if (AppConfig.isShowRSS) {
+                bottomNavigationView.menu.getItem(position).isChecked = true
+            } else {
+                bottomNavigationView.menu.getItem(3).isChecked = true
+            }
+        }
+    }
+
     override fun onKeyUp(keyCode: Int, event: KeyEvent?): Boolean {
         event?.let {
             when (keyCode) {
@@ -186,29 +186,36 @@ class MainActivity : VMBaseActivity<ActivityMainBinding, MainViewModel>(),
         }
     }
 
-    private inner class TabFragmentPageAdapter :
+    private inner class TabFragmentPageAdapter(fm: FragmentManager) :
-        FragmentStateAdapter(this) {
+        FragmentStatePagerAdapter(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
 
-        override fun getItemId(position: Int): Long {
+        private fun getId(position: Int): Int {
             return when (position) {
                 2 -> if (AppConfig.isShowRSS) 2 else 3
-                else -> position.toLong()
+                else -> position
             }
         }
 
-        override fun getItemCount(): Int {
+        override fun getItemPosition(`object`: Any): Int {
-            return if (AppConfig.isShowRSS) 4 else 3
+            return POSITION_NONE
         }
 
-        override fun createFragment(position: Int): Fragment {
+        override fun getItem(position: Int): Fragment {
-            val id = getItemId(position)
+            return when (getId(position)) {
-            val fragment = when (id) {
+                0 -> BookshelfFragment()
-                0L -> BookshelfFragment()
+                1 -> ExploreFragment()
-                1L -> ExploreFragment()
+                2 -> RssFragment()
-                2L -> RssFragment()
                 else -> MyFragment()
             }
-            fragmentMap[id] = fragment
+        }
+
+        override fun getCount(): Int {
+            return if (AppConfig.isShowRSS) 4 else 3
+        }
+
+        override fun instantiateItem(container: ViewGroup, position: Int): Any {
+            val fragment = super.instantiateItem(container, position) as Fragment
+            fragmentMap[getId(position)] = fragment
             return fragment
         }
 

app/src/main/java/io/legado/app/ui/main/bookshelf/BookshelfFragment.kt

@@ -7,13 +7,11 @@ import android.os.Bundle
 import android.view.Menu
 import android.view.MenuItem
 import android.view.View
+import android.view.ViewGroup
 import androidx.appcompat.widget.SearchView
 import androidx.fragment.app.*
 import androidx.lifecycle.LiveData
-import androidx.viewpager2.adapter.FragmentStateAdapter
-import androidx.viewpager2.widget.ViewPager2
 import com.google.android.material.tabs.TabLayout
-import com.google.android.material.tabs.TabLayoutMediator
 import io.legado.app.R
 import io.legado.app.base.VMBaseFragment
 import io.legado.app.constant.AppConst
@@ -33,7 +31,6 @@ import io.legado.app.ui.book.local.ImportBookActivity
 import io.legado.app.ui.book.search.SearchActivity
 import io.legado.app.ui.filepicker.FilePicker
 import io.legado.app.ui.filepicker.FilePickerDialog
-import io.legado.app.ui.main.MainActivity
 import io.legado.app.ui.main.MainViewModel
 import io.legado.app.ui.main.bookshelf.books.BooksFragment
 import io.legado.app.utils.*
@@ -51,18 +48,12 @@ class BookshelfFragment : VMBaseFragment<BookshelfViewModel>(R.layout.fragment_b
     private val binding by viewBinding(FragmentBookshelfBinding::bind)
     override val viewModel: BookshelfViewModel by viewModels()
     private val activityViewModel: MainViewModel by activityViewModels()
+    private lateinit var adapter: FragmentStatePagerAdapter
     private lateinit var tabLayout: TabLayout
     private var bookGroupLiveData: LiveData<List<BookGroup>>? = null
     private val bookGroups = mutableListOf<BookGroup>()
     private val fragmentMap = hashMapOf<Long, BooksFragment>()
 
-    private var currentPosition = 0     //当前滑动位置
-    private var oldPosition = 0          //上一个滑动位置
-    private var currentState = 0        //记录当前手指按下状态
-    private var scrolledPixList = mutableListOf<Int>() //记录手指滑动时的像素坐标记录
-
-    private val mainActivity get() = activity as MainActivity
-
     override fun onFragmentCreated(view: View, savedInstanceState: Bundle?) {
         tabLayout = binding.titleBar.findViewById(R.id.tab_layout)
         setSupportToolbar(binding.titleBar.toolbar)
@@ -110,64 +101,15 @@ class BookshelfFragment : VMBaseFragment<BookshelfViewModel>(R.layout.fragment_b
     private val selectedGroup: BookGroup
         get() = bookGroups[tabLayout.selectedTabPosition]
 
-    private fun initView() = with(binding) {
+    private fun initView() {
-        ATH.applyEdgeEffectColor(viewPagerBookshelf)
+        ATH.applyEdgeEffectColor(binding.viewPagerBookshelf)
         tabLayout.isTabIndicatorFullWidth = false
         tabLayout.tabMode = TabLayout.MODE_SCROLLABLE
         tabLayout.setSelectedTabIndicatorColor(requireContext().accentColor)
-        viewPagerBookshelf.offscreenPageLimit = 1
+        tabLayout.setupWithViewPager(binding.viewPagerBookshelf)
-        viewPagerBookshelf.adapter = TabFragmentPageAdapter()
+        binding.viewPagerBookshelf.offscreenPageLimit = 1
-        TabLayoutMediator(tabLayout, viewPagerBookshelf) { tab, i ->
+        adapter = TabFragmentPageAdapter(childFragmentManager)
-            tab.text = bookGroups[i].groupName
+        binding.viewPagerBookshelf.adapter = adapter
-        }.attach()
-        viewPagerBookshelf.registerOnPageChangeCallback(object : ViewPager2.OnPageChangeCallback() {
-            //页面滚动的位置信息回调： position 当前滚动到哪个页面，positionOffset 位置偏移百分比, positionOffsetPixels 当前所在页面偏移量
-            //此回调会触发完onPageScrollStateChanged 的 state 值为1时后面才触发回调
-            override fun onPageScrolled(
-                position: Int,
-                positionOffset: Float,
-                positionOffsetPixels: Int
-            ) {
-                currentPosition = position
-                if (currentState == 1) {
-                    //手指按下滑动坐标记录
-                    scrolledPixList.add(positionOffsetPixels)
-                }
-            }
-
-
-            // 滚动状态改变回调，state的值分别有0，1，2 ;
-            // 0为ViewPager所有事件(1,2)已结束触发
-            // 1为在viewPager里按下并滑动触发多次
-            // 2是手指抬起触发
-            override fun onPageScrollStateChanged(state: Int) {
-                currentState = state
-                if (state == 0) {
-                    if (currentPosition == oldPosition) {
-                        when (currentPosition) {
-                            0 -> {
-                                if (scrolledPixList.size > 1 && scrolledPixList.last() == 0 || scrolledPixList.last() - scrolledPixList[0] > 0) {
-                                    //有可能出现滑到一半放弃的情况也是可以出现currentPosition == oldPositon=0，则先判断是否是往右滑时放弃
-                                    return
-                                }
-                                //若还有上一个bottom fragment页面则切换
-                                mainActivity.viewPager.currentItem.takeIf { it > 0 }
-                                    ?.also { mainActivity.viewPager.setCurrentItem(it - 1, true) }
-                            }
-
-                            (viewPagerBookshelf.adapter as FragmentStateAdapter).itemCount - 1 -> {
-                                //若还有下一个bottom fragment页面则切换
-                                mainActivity.viewPager.currentItem.takeIf { it < mainActivity.viewPager.adapter!!.itemCount - 1 }
-                                    ?.also { mainActivity.viewPager.setCurrentItem(it + 1, true) }
-                            }
-                        }
-                    }
-                    oldPosition = currentPosition
-                    scrolledPixList.clear()//清空滑动记录
-                }
-            }
-
-        })
     }
 
     private fun initBookGroupData() {
@@ -199,7 +141,7 @@ class BookshelfFragment : VMBaseFragment<BookshelfViewModel>(R.layout.fragment_b
             if (data != bookGroups) {
                 bookGroups.clear()
                 bookGroups.addAll(data)
-                binding.viewPagerBookshelf.adapter?.notifyDataSetChanged()
+                adapter.notifyDataSetChanged()
                 selectLastTab()
             }
         }
@@ -309,21 +251,29 @@ class BookshelfFragment : VMBaseFragment<BookshelfViewModel>(R.layout.fragment_b
         }
     }
 
-    private inner class TabFragmentPageAdapter :
+    private inner class TabFragmentPageAdapter(fm: FragmentManager) :
-        FragmentStateAdapter(this) {
+        FragmentStatePagerAdapter(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
+
+        override fun getPageTitle(position: Int): CharSequence {
+            return bookGroups[position].groupName
+        }
+
+        override fun getItemPosition(`object`: Any): Int {
+            return POSITION_NONE
+        }
 
-        override fun getItemId(position: Int): Long {
+        override fun getItem(position: Int): Fragment {
             val group = bookGroups[position]
-            return group.groupId
+            return BooksFragment.newInstance(position, group.groupId)
         }
 
-        override fun getItemCount(): Int {
+        override fun getCount(): Int {
             return bookGroups.size
         }
 
-        override fun createFragment(position: Int): Fragment {
+        override fun instantiateItem(container: ViewGroup, position: Int): Any {
+            val fragment = super.instantiateItem(container, position) as BooksFragment
             val group = bookGroups[position]
-            val fragment = BooksFragment.newInstance(position, group.groupId)
             fragmentMap[group.groupId] = fragment
             return fragment
         }

app/src/main/res/layout/activity_main.xml

@@ -5,7 +5,7 @@
     android:layout_height="match_parent"
     android:orientation="vertical">
 
-    <androidx.viewpager2.widget.ViewPager2
+    <androidx.viewpager.widget.ViewPager
         android:id="@+id/view_pager_main"
         android:layout_width="match_parent"
         android:layout_height="0dp"

app/src/main/res/layout/fragment_bookshelf.xml

@@ -13,7 +13,7 @@
         app:title="@string/bookshelf"
         app:contentLayout="@layout/view_tab_layout_min" />
 
-    <androidx.viewpager2.widget.ViewPager2
+    <androidx.viewpager.widget.ViewPager
         android:id="@+id/view_pager_bookshelf"
         android:layout_width="match_parent"
         android:layout_height="match_parent" />