优化

app/src/main/java/io/legado/app/help/storage/AppWebDav.kt

@@ -130,6 +130,14 @@ object AppWebDav {
         }
     }
 
+    suspend fun hasBackUp(): Boolean {
+        authorization?.let {
+            val url = "${rootWebDavUrl}${backupFileName}"
+            return WebDav(url, it).exists()
+        }
+        return false
+    }
+
     suspend fun lastBackUp(): WebDavFile? {
         authorization?.let {
             var lastBackupFile: WebDavFile? = null

app/src/main/java/io/legado/app/help/storage/Backup.kt

@@ -51,8 +51,7 @@ object Backup {
         val lastBackup = LocalConfig.lastBackup
         if (lastBackup + TimeUnit.DAYS.toMillis(1) < System.currentTimeMillis()) {
             Coroutine.async {
-                val lastBackupWebDav = AppWebDav.lastBackUp()
-                if (lastBackupWebDav == null || lastBackup > lastBackupWebDav.lastModify.time) {
+                if (!AppWebDav.hasBackUp()) {
                     backup(context, context.getPrefString(PreferKey.backupPath), true)
                 } else {
                     LocalConfig.lastBackup = System.currentTimeMillis()