allow preloading all pages

Author: lohanidamodar

example/lib/main.dart

@@ -74,9 +74,11 @@ class _MyAppState extends State<MyApp> {
               ? Center(child: CircularProgressIndicator())
               : PDFViewer(
                   document: document,
+                  //uncomment below line to preload all pages
+                  // lazyLoad: false,
                   // uncomment below line to scroll vertically
                   // scrollDirection: Axis.vertical,
-                  
+
                   //uncomment below code to replace bottom navigation with your own
                   /* navigationBuilder:
                       (context, page, totalPages, jumpToPage, animateToPage) {

lib/src/document.dart

@@ -12,6 +12,8 @@ class PDFDocument {
 
   String _filePath;
   int count;
+  List<PDFPage> _pages = [];
+  bool _preloaded = false;
 
   /// Load a PDF File from a given File
   ///
@@ -81,6 +83,7 @@ class PDFDocument {
   Future<PDFPage> get(
       {int page = 1, final Function(double) onZoomChanged}) async {
     assert(page > 0);
+    if (_preloaded && _pages.isNotEmpty) return _pages[page - 1];
     var data = await _channel
         .invokeMethod('getPage', {'filePath': _filePath, 'pageNumber': page});
     return new PDFPage(
@@ -90,6 +93,21 @@ class PDFDocument {
     );
   }
 
+  Future<void> preloadPages({final Function(double) onZoomChanged}) async {
+    int countvar = 1;
+    await Future.forEach<int>(List(count), (i) async {
+      final data = await _channel.invokeMethod(
+          'getPage', {'filePath': _filePath, 'pageNumber': countvar});
+      _pages.add(PDFPage(
+        data,
+        countvar,
+        onZoomChanged: onZoomChanged,
+      ));
+      countvar++;
+    });
+    _preloaded = true;
+  }
+
   // Stream all pages
   Stream<PDFPage> getAll({final Function(double) onZoomChanged}) {
     return Future.forEach<PDFPage>(List(count), (i) async {

lib/src/viewer.dart

@@ -15,6 +15,7 @@ class PDFViewer extends StatefulWidget {
   final PDFViewerTooltip tooltip;
   final bool enableSwipeNavigation;
   final Axis scrollDirection;
+  final bool lazyLoad;
   final Widget Function(
     BuildContext,
     int pageNumber,
@@ -27,6 +28,7 @@ class PDFViewer extends StatefulWidget {
       {Key key,
       @required this.document,
       this.scrollDirection,
+      this.lazyLoad = true,
       this.indicatorText = Colors.white,
       this.indicatorBackground = Colors.black54,
       this.showIndicator = true,
@@ -55,6 +57,8 @@ class _PDFViewerState extends State<PDFViewer> {
     super.initState();
     _pages = List(widget.document.count);
     _pageController = PageController();
+    if (!widget.lazyLoad)
+      widget.document.preloadPages(onZoomChanged: onZoomChanged);
   }
 
   @override