info: handle back button to image page

lib/widgets/fullscreen/image_page.dart

@@ -30,13 +30,7 @@ class FullscreenPage extends AnimatedWidget {
 
   @override
   Widget build(BuildContext context) {
-    return WillPopScope(
+    return Scaffold(
-      onWillPop: () {
-        Screen.keepOn(false);
-        SystemChrome.setEnabledSystemUIOverlays(SystemUiOverlay.values);
-        return Future.value(true);
-      },
-      child: Scaffold(
       backgroundColor: Colors.black,
       body: FullscreenBody(
         collection: collection,
@@ -71,7 +65,6 @@ class FullscreenPage extends AnimatedWidget {
 //            ],
 //          ),
 //        ),
-      ),
     );
   }
 }
@@ -145,7 +138,17 @@ class FullscreenBodyState extends State<FullscreenBody> with SingleTickerProvide
   @override
   Widget build(BuildContext context) {
     final entry = entries[_currentHorizontalPage];
-    return Stack(
+    return WillPopScope(
+      onWillPop: () {
+        if (_currentVerticalPage == 1) {
+          goToVerticalPage(0);
+          return Future.value(false);
+        }
+        Screen.keepOn(false);
+        SystemChrome.setEnabledSystemUIOverlays(SystemUiOverlay.values);
+        return Future.value(true);
+      },
+      child: Stack(
         children: [
           PageView(
             scrollDirection: Axis.vertical,
@@ -192,6 +195,7 @@ class FullscreenBodyState extends State<FullscreenBody> with SingleTickerProvide
             )
           ]
         ],
+      ),
     );
   }