优化

app/src/main/java/io/legado/app/model/ReadBook.kt

@@ -26,6 +26,7 @@ import io.legado.app.help.globalExecutor
 import io.legado.app.model.localBook.TextFile
 import io.legado.app.model.webBook.WebBook
 import io.legado.app.service.BaseReadAloudService
+import io.legado.app.service.CacheBookService
 import io.legado.app.ui.book.read.page.entities.TextChapter
 import io.legado.app.ui.book.read.page.provider.ChapterProvider
 import io.legado.app.ui.book.read.page.provider.LayoutProgressListener
@@ -956,6 +957,9 @@ object ReadBook : CoroutineScope by MainScope() {
         downloadedChapters.clear()
         downloadFailChapters.clear()
         ImageProvider.clear()
+        if (!CacheBookService.isRun) {
+            CacheBook.close()
+        }
     }
 
     interface CallBack : LayoutProgressListener {

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

@@ -202,6 +202,7 @@ class MainViewModel(application: Application) : BaseViewModel(application) {
      * 缓存书籍
      */
     private fun cacheBook() {
+        if (AppConfig.preDownloadNum == 0) return
         cacheBookJob?.cancel()
         cacheBookJob = viewModelScope.launch(upTocPool) {
             while (isActive) {