优化

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

@@ -60,12 +60,14 @@ object BookHelp {
                 DocumentUtils.getDirDocument(
                     root,
                     subDirs = *arrayOf(cacheFolderName, bookFolderName(book))
-                )?.listFiles()?.forEach {
+                )?.uri?.let { uri ->
-                    if (it.name?.startsWith(String.format("%05d", bookChapter.index)) == true) {
+                    DocumentUtils.listFiles(App.INSTANCE, uri).forEach {
-                        it.delete()
+                        if (it.name.startsWith(String.format("%05d", bookChapter.index))) {
+                            DocumentFile.fromSingleUri(App.INSTANCE, it.uri)?.delete()
                             return@forEach
                         }
                     }
+                }
                 DocumentUtils.createFileIfNotExist(
                     root,
                     "${bookChapterName(bookChapter)}.nb",