优化 EPUB 翻页与后台分页刷新

Sources/RDReaderView/ReaderView/Paging/RDReaderPreloadController.swift

@@ -78,8 +78,12 @@ final class RDReaderPreloadController {
         environment: Environment,
         contentViewProvider: (Int, UIView?) -> UIView?
     ) -> UIView {
-        let reusableView = detachedReusablePageView(for: pageNum)
-        let view = contentViewProvider(pageNum, reusableView) ?? reusableView ?? UIView()
+        let view: UIView
+        if let reusableView = detachedReusablePageView(for: pageNum) {
+            view = reusableView
+        } else {
+            view = contentViewProvider(pageNum, nil) ?? UIView()
+        }
         if shouldCache(view: view, for: pageNum, environment: environment) {
             pageCurlCachedViews[pageNum] = view
         } else {
@@ -111,8 +115,14 @@ final class RDReaderPreloadController {
         preloadHostView.frame = parentView.bounds
 
         for targetPage in targets {
-            let existing = detachedReusablePageView(for: targetPage)
-            let contentView = contentViewProvider(targetPage, existing) ?? existing ?? UIView()
+            let contentView: UIView
+            if let existing = preloadedPageViews[targetPage], existing.superview === preloadHostView {
+                contentView = existing
+            } else if let cached = pageCurlCachedViews.removeValue(forKey: targetPage), cached.superview == nil {
+                contentView = cached
+            } else {
+                contentView = contentViewProvider(targetPage, nil) ?? UIView()
+            }
             let shouldCacheContentView = shouldCache(view: contentView, for: targetPage, environment: environment)
             if shouldCacheContentView {
                 preloadedPageViews[targetPage] = contentView