修复fragment复用引起的双击书架到顶端在切换主题模式后失效的bug

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

@@ -3,6 +3,7 @@ package io.legado.app.ui.main
 import android.os.Bundle
 import android.view.KeyEvent
 import android.view.MenuItem
+import android.view.ViewGroup
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.FragmentManager
 import androidx.fragment.app.FragmentStatePagerAdapter
@@ -28,6 +29,7 @@ import io.legado.app.utils.*
 import kotlinx.android.synthetic.main.activity_main.*
 import org.jetbrains.anko.toast
 
+
 class MainActivity : VMBaseActivity<MainViewModel>(R.layout.activity_main),
     BottomNavigationView.OnNavigationItemSelectedListener,
     BottomNavigationView.OnNavigationItemReselectedListener,
@@ -37,13 +39,7 @@ class MainActivity : VMBaseActivity<MainViewModel>(R.layout.activity_main),
     private var exitTime: Long = 0
     private var bookshelfReselected: Long = 0
     private var pagePosition = 0
-    private val fragmentId = arrayOf(0, 1, 2, 3)
+    private val fragmentMap = hashMapOf<Int, Fragment>()
-    private val fragmentMap = mapOf(
-        Pair(fragmentId[0], BookshelfFragment()),
-        Pair(fragmentId[1], ExploreFragment()),
-        Pair(fragmentId[2], RssFragment()),
-        Pair(fragmentId[3], MyFragment())
-    )
 
     override fun onActivityCreated(savedInstanceState: Bundle?) {
         ATH.applyEdgeEffectColor(view_pager_main)
@@ -171,20 +167,48 @@ class MainActivity : VMBaseActivity<MainViewModel>(R.layout.activity_main),
     private inner class TabFragmentPageAdapter(fm: FragmentManager) :
         FragmentStatePagerAdapter(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
 
+        private fun getBookshelfFragment(): Fragment {
+            if (!fragmentMap.containsKey(0)) {
+                fragmentMap[0] = BookshelfFragment()
+            }
+            return fragmentMap.getValue(0)
+        }
+
+        private fun getExploreFragment(): Fragment {
+            if (!fragmentMap.containsKey(1)) {
+                fragmentMap[1] = ExploreFragment()
+            }
+            return fragmentMap.getValue(1)
+        }
+
+        private fun getRssFragment(): Fragment {
+            if (!fragmentMap.containsKey(2)) {
+                fragmentMap[2] = RssFragment()
+            }
+            return fragmentMap.getValue(2)
+        }
+
+        private fun getMyFragment(): Fragment {
+            if (!fragmentMap.containsKey(3)) {
+                fragmentMap[3] = MyFragment()
+            }
+            return fragmentMap.getValue(3)
+        }
+
         override fun getItemPosition(`object`: Any): Int {
             return POSITION_NONE
         }
 
         override fun getItem(position: Int): Fragment {
             return when (position) {
-                0 -> fragmentMap.getValue(fragmentId[0])
+                0 -> getBookshelfFragment()
-                1 -> fragmentMap.getValue(fragmentId[1])
+                1 -> getExploreFragment()
                 2 -> if (AppConfig.isShowRSS) {
-                    fragmentMap.getValue(fragmentId[2])
+                    getRssFragment()
                 } else {
-                    fragmentMap.getValue(fragmentId[3])
+                    getMyFragment()
                 }
-                else -> fragmentMap.getValue(fragmentId[3])
+                else -> getMyFragment()
             }
         }
 
@@ -192,6 +216,18 @@ class MainActivity : VMBaseActivity<MainViewModel>(R.layout.activity_main),
             return if (AppConfig.isShowRSS) 4 else 3
         }
 
+        override fun instantiateItem(container: ViewGroup, position: Int): Any {
+            val fragment = super.instantiateItem(container, position) as Fragment
+            val id = when (position) {
+                2 -> if (AppConfig.isShowRSS) 2 else 3
+                else -> position
+            }
+            if (!fragmentMap.containsKey(id)) {
+                fragmentMap[id] = fragment
+            }
+            return fragment
+        }
+
     }
 
 }

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

@@ -2,10 +2,7 @@ package io.legado.app.ui.main.bookshelf
 
 import android.annotation.SuppressLint
 import android.os.Bundle
-import android.view.LayoutInflater
+import android.view.*
-import android.view.Menu
-import android.view.MenuItem
-import android.view.View
 import androidx.appcompat.widget.SearchView
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.FragmentManager
@@ -294,5 +291,14 @@ class BookshelfFragment : VMBaseFragment<BookshelfViewModel>(R.layout.fragment_b
             return bookGroups.size
         }
 
+        override fun instantiateItem(container: ViewGroup, position: Int): Any {
+            val fragment = super.instantiateItem(container, position) as BooksFragment
+            val group = bookGroups[position]
+            if (!fragmentMap.containsKey(group.groupId)) {
+                fragmentMap[group.groupId] = fragment
+            }
+            return fragment
+        }
+
     }
 }