优化

app/src/main/java/io/legado/app/help/BookHelp.kt

@@ -83,7 +83,7 @@ object BookHelp {
     fun getChapterCount(book: Book): Int {
         if (downloadUri.isDocumentUri(App.INSTANCE)) {
             DocumentFile.fromTreeUri(App.INSTANCE, downloadUri)?.let {
-                return DocumentUtils.createFileIfNotExist(
+                return DocumentUtils.createFolderIfNotExist(
                     it,
                     subDirs = *arrayOf(cacheFolderName, bookFolderName(book))
                 )?.listFiles()?.size ?: 0

app/src/main/java/io/legado/app/utils/DocumentUtils.kt

@@ -17,11 +17,11 @@ object DocumentUtils {
         mimeType: String = "",
         vararg subDirs: String
     ): DocumentFile? {
-        val parent: DocumentFile? = createFileIfNotExist(root, *subDirs)
+        val parent: DocumentFile? = createFolderIfNotExist(root, *subDirs)
         return parent?.createFile(mimeType, fileName)
     }
 
-    fun createFileIfNotExist(root: DocumentFile, vararg subDirs: String): DocumentFile? {
+    fun createFolderIfNotExist(root: DocumentFile, vararg subDirs: String): DocumentFile? {
         var parent: DocumentFile? = root
         for (subDirName in subDirs) {
             val subDir = parent?.findFile(subDirName)