Update method write file sync.

example/test/viewer_test.dart

@@ -0,0 +1,59 @@
+import 'dart:io';
+
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter_plugin_pdf_viewer/flutter_plugin_pdf_viewer.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  const MethodChannel channel = MethodChannel('flutter_plugin_pdf_viewer');
+  List<MethodCall> log;
+
+  channel.setMockMethodCallHandler((MethodCall methodCall) async {
+    log.add(methodCall);
+    switch (methodCall.method) {
+      case 'getNumberOfPages':
+        return '5';
+      default:
+        return null;
+    }
+  });
+
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  const MethodChannel channelPath =
+  MethodChannel('plugins.flutter.io/path_provider');
+  List<MethodCall> logPath;
+
+  channelPath.setMockMethodCallHandler((MethodCall methodCall) async {
+    logPath.add(methodCall);
+    switch (methodCall.method) {
+      case 'getApplicationDocumentsDirectory':
+        return Directory.current.path;
+      default:
+        return null;
+    }
+  });
+
+  setUp(() {
+    logPath = <MethodCall>[];
+    log = <MethodCall>[];
+  });
+
+  Widget createWidgetForTesting({Widget child}) {
+    return MaterialApp(
+      home: child,
+    );
+  }
+
+  testWidgets('PDFViewer with BottomAppBar', (WidgetTester tester) async {
+    PDFDocument _document = await PDFDocument.fromAsset('assets/sample2.pdf');
+    await tester.pumpWidget(
+        createWidgetForTesting(child: PDFViewer(document: _document)));
+
+    var bottomBar = find.byType(BottomAppBar);
+    expect(bottomBar, findsOneWidget);
+  });
+}

lib/src/document.dart

@@ -59,7 +59,7 @@ class PDFDocument {
       file = File("${dir.path}/file.pdf");
       var data = await rootBundle.load(asset);
       var bytes = data.buffer.asUint8List();
-      await file.writeAsBytes(bytes, flush: true);
+      file.writeAsBytesSync(bytes, flush: true);
     } catch (e) {
       throw Exception('Error parsing asset file!');
     }