优化

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

@@ -136,6 +136,11 @@ class MainActivity : VMBaseActivity<ActivityMainBinding, MainViewModel>(),
                         binding.viewPagerMain.currentItem = 0
                         return true
                     }
+                    (fragmentMap[getFragmentId(0)] as? BookshelfFragment2)?.let {
+                        if (it.back()) {
+                            return true
+                        }
+                    }
                     if (System.currentTimeMillis() - exitTime > 2000) {
                         toastOnUi(R.string.double_click_exit)
                         exitTime = System.currentTimeMillis()

app/src/main/java/io/legado/app/ui/main/bookshelf/style2/BookshelfFragment2.kt

@@ -140,6 +140,15 @@ class BookshelfFragment2 : BaseBookshelfFragment(R.layout.fragment_bookshelf1),
         }
     }
 
+    fun back(): Boolean {
+        if (groupId != AppConst.bookGroupNoneId) {
+            groupId = AppConst.bookGroupNoneId
+            initBooksData()
+            return true
+        }
+        return false
+    }
+
     override fun onQueryTextSubmit(query: String?): Boolean {
         SearchActivity.start(requireContext(), query)
         return false