diff --git a/app/src/main/java/io/legado/app/model/localBook/EPUBFile.kt b/app/src/main/java/io/legado/app/model/localBook/EPUBFile.kt
index 6bdfd5b64..84876de18 100644
--- a/app/src/main/java/io/legado/app/model/localBook/EPUBFile.kt
+++ b/app/src/main/java/io/legado/app/model/localBook/EPUBFile.kt
@@ -21,7 +21,7 @@ class EPUBFile(val book: io.legado.app.data.entities.Book) {
         private var eFile: EPUBFile? = null
 
         @Synchronized
-        fun getEFile(book: io.legado.app.data.entities.Book): EPUBFile {
+        private fun getEFile(book: io.legado.app.data.entities.Book): EPUBFile {
             if (eFile == null || eFile?.book?.bookUrl != book.bookUrl) {
                 eFile = EPUBFile(book)
                 return eFile!!
@@ -29,10 +29,12 @@ class EPUBFile(val book: io.legado.app.data.entities.Book) {
             return eFile!!
         }
 
+        @Synchronized
         fun getChapterList(book: io.legado.app.data.entities.Book): ArrayList<BookChapter> {
             return getEFile(book).getChapterList()
         }
 
+        @Synchronized
         fun getContent(book: io.legado.app.data.entities.Book, chapter: BookChapter): String? {
             return getEFile(book).getContent(chapter)
         }
@@ -55,7 +57,7 @@ class EPUBFile(val book: io.legado.app.data.entities.Book) {
         }
     }
 
-    fun getContent(chapter: BookChapter): String? {
+    private fun getContent(chapter: BookChapter): String? {
         epubBook?.let { eBook ->
             val resource = eBook.resources.getByHref(chapter.url)
             val content = StringBuilder()
@@ -82,7 +84,7 @@ class EPUBFile(val book: io.legado.app.data.entities.Book) {
         return null
     }
 
-    fun getChapterList(): ArrayList<BookChapter> {
+    private fun getChapterList(): ArrayList<BookChapter> {
         val chapterList = ArrayList<BookChapter>()
         epubBook?.let { eBook ->
             val metadata = eBook.metadata