优化

app/src/main/java/io/legado/app/ui/book/changecover/ChangeCoverViewModel.kt

@@ -137,6 +137,7 @@ class ChangeCoverViewModel(application: Application) : BaseViewModel(application
             )
         ) {
             searchStateData.postValue(false)
+            tasks.clear()
         }
     }
 

app/src/main/java/io/legado/app/ui/book/changesource/ChangeSourceViewModel.kt

@@ -163,10 +163,13 @@ class ChangeSourceViewModel(application: Application) : BaseViewModel(applicatio
                         || searchIndex >= bookSourceList.lastIndex + threadCount
                     ) {
                         searchStateData.postValue(false)
+                        tasks.clear()
                     }
                 }
+
             }
         tasks.add(task)
+
     }
 
     private fun loadBookInfo(webBook: WebBook, book: Book) {