Cache error, late initialization error

example/android/app/build.gradle

@@ -26,7 +26,7 @@ apply plugin: 'kotlin-android'
 apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
 android {
-    compileSdkVersion 29
+    compileSdkVersion 31
 
     sourceSets {
         main.java.srcDirs += 'src/main/kotlin'
@@ -43,7 +43,7 @@ android {
         // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
         applicationId "jp.espresso3389.pdf_render_example"
         minSdkVersion 21
-        targetSdkVersion 28
+        targetSdkVersion 31
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
     }

example/android/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.3.50'
+    ext.kotlin_version = '1.4.10'
     repositories {
         google()
         jcenter()

example/lib/main.dart

@@ -56,6 +56,7 @@ class _MyAppState extends State<MyApp> {
                 params: const PdfViewerParams(
                   padding: 10,
                   minScale: 1.0,
+                  // scrollDirection: Axis.horizontal,
                 ),
               ),
         floatingActionButton: Column(

example/pubspec.lock

@@ -141,7 +141,7 @@ packages:
       name: material_color_utilities
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.1.3"
+    version: "0.1.2"
   meta:
     dependency: transitive
     description:

lib/pdf_render_widgets.dart

@@ -60,19 +60,17 @@ class _PdfDocumentAwaiter {
 
   final FutureOr<PdfDocument> _docFuture;
   final OnError? onError;
-  late PdfDocument _cached;
-  bool _firstTime = true;
+  PdfDocument? _cached;
 
   Future<PdfDocument> getValue() async {
-    if (_firstTime) {
-      _firstTime = false;
+    if (_cached == null) {
       try {
         _cached = await _docFuture;
       } catch (e) {
         onError?.call(e);
       }
     }
-    return _cached;
+    return _cached!;
   }
 }
 
@@ -193,7 +191,9 @@ class _PdfDocumentLoaderState extends State<PdfDocumentLoader> {
   void _setPageSize(int pageNumber, Size? size) {
     _lastPageSize = size;
     if (pageNumber > 0 && pageNumber <= _doc!.pageCount) {
-      _cachedPageSizes ??= List<Size?>.filled(_doc!.pageCount, null);
+      if (_cachedPageSizes == null || _cachedPageSizes?.length != _doc!.pageCount) {
+        _cachedPageSizes = List<Size?>.filled(_doc!.pageCount, null);
+      }
       _cachedPageSizes![pageNumber - 1] = size;
     }
   }
@@ -549,6 +549,9 @@ class PdfViewerParams {
   /// Custom page decoration such as drop-shadow.
   final BoxDecoration? pageDecoration;
 
+  /// Scrolling direction.
+  final Axis scrollDirection;
+
   /// See [InteractiveViewer] for more info.
   final bool alignPanAxis;
 
@@ -587,6 +590,7 @@ class PdfViewerParams {
     this.buildPagePlaceholder,
     this.buildPageOverlay,
     this.pageDecoration,
+    this.scrollDirection = Axis.vertical,
     this.alignPanAxis = false,
     this.boundaryMargin = EdgeInsets.zero,
     this.maxScale = 20,
@@ -606,6 +610,7 @@ class PdfViewerParams {
     BuildPageContentFunc? buildPagePlaceholder,
     BuildPageContentFunc? buildPageOverlay,
     BoxDecoration? pageDecoration,
+    Axis? scrollDirection,
     bool? alignPanAxis,
     EdgeInsets? boundaryMargin,
     bool? panEnabled,
@@ -624,6 +629,7 @@ class PdfViewerParams {
         buildPagePlaceholder: buildPagePlaceholder ?? this.buildPagePlaceholder,
         buildPageOverlay: buildPageOverlay ?? this.buildPageOverlay,
         pageDecoration: pageDecoration ?? this.pageDecoration,
+        scrollDirection: scrollDirection ?? this.scrollDirection,
         alignPanAxis: alignPanAxis ?? this.alignPanAxis,
         boundaryMargin: boundaryMargin ?? this.boundaryMargin,
         panEnabled: panEnabled ?? this.panEnabled,
@@ -647,6 +653,7 @@ class PdfViewerParams {
         other.buildPagePlaceholder == buildPagePlaceholder &&
         other.buildPageOverlay == buildPageOverlay &&
         other.pageDecoration == pageDecoration &&
+        other.scrollDirection == scrollDirection &&
         other.alignPanAxis == alignPanAxis &&
         other.boundaryMargin == boundaryMargin &&
         other.panEnabled == panEnabled &&
@@ -667,6 +674,7 @@ class PdfViewerParams {
         buildPagePlaceholder.hashCode ^
         buildPageOverlay.hashCode ^
         pageDecoration.hashCode ^
+        scrollDirection.hashCode ^
         alignPanAxis.hashCode ^
         boundaryMargin.hashCode ^
         panEnabled.hashCode ^
@@ -974,19 +982,34 @@ class _PdfViewerState extends State<PdfViewer> with SingleTickerProviderStateMix
     _determinePagesToShow();
   }
 
-  /// Default page layout logic that layouts pages vertically.
+  /// Default page layout logic that layouts pages vertically or horizontally.
   void _relayoutDefault(Size viewSize) {
-    final maxWidth = _pages!.fold<double>(0.0, (maxWidth, page) => max(maxWidth, page.pageSize.width));
-    final ratio = (viewSize.width - _padding * 2) / maxWidth;
-    var top = _padding;
-    for (int i = 0; i < _pages!.length; i++) {
-      final page = _pages![i];
-      final w = page.pageSize.width * ratio;
-      final h = page.pageSize.height * ratio;
-      page.rect = Rect.fromLTWH(_padding, top, w, h);
-      top += h + _padding;
-    }
-    _docSize = Size(viewSize.width, top);
+      if (widget.params?.scrollDirection == Axis.horizontal) {
+        final maxHeight = _pages!.fold<double>(0.0, (maxHeight, page) => max(maxHeight, page.pageSize.height));
+        final ratio = (viewSize.height - _padding * 2) / maxHeight;
+        var left = _padding;
+        for (int i = 0; i < _pages!.length; i++) {
+          final page = _pages![i];
+          final w = page.pageSize.width * ratio;
+          final h = page.pageSize.height * ratio;
+          page.rect = Rect.fromLTWH(left, _padding, w, h);
+          left += w + _padding;
+        }
+        _docSize = Size(left, viewSize.height);
+      }
+      else {
+        final maxWidth = _pages!.fold<double>(0.0, (maxWidth, page) => max(maxWidth, page.pageSize.width));
+        final ratio = (viewSize.width - _padding * 2) / maxWidth;
+        var top = _padding;
+        for (int i = 0; i < _pages!.length; i++) {
+          final page = _pages![i];
+          final w = page.pageSize.width * ratio;
+          final h = page.pageSize.height * ratio;
+          page.rect = Rect.fromLTWH(_padding, top, w, h);
+          top += h + _padding;
+        }
+        _docSize = Size(viewSize.width, top);
+      }
   }
 
   Iterable<Widget> iterateLaidOutPages(Size viewSize) sync* {

pubspec.lock

@@ -99,7 +99,7 @@ packages:
       name: material_color_utilities
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.1.3"
+    version: "0.1.2"
   meta:
     dependency: transitive
     description: