remove `Dismissible` and instead use `GestureDetector` for dismissal

lib/pages/media_view.dart

@@ -87,30 +87,26 @@ class MediaViewPage extends HookWidget {
               ],
             )
           : null,
-      body: Dismissible(
+      body: GestureDetector(
-        direction: DismissDirection.vertical,
+        onTapUp: (details) => showButtons.value = !showButtons.value,
-        onDismissed: (_) => Navigator.of(context).pop(),
+        onVerticalDragEnd: isZoomedOut.value
-        key: const Key('media view'),
+            ? (details) {
-        background: Container(color: Colors.black),
+                if (details.primaryVelocity.abs() > 1000) {
-        dismissThresholds: {
+                  Navigator.of(context).pop();
-          DismissDirection.vertical: 0,
+                }
-        },
+              }
-        confirmDismiss: (direction) => Future.value(isZoomedOut.value),
+            : null,
-        resizeDuration: null,
+        child: PhotoView(
-        child: GestureDetector(
+          scaleStateChangedCallback: (value) {
-          onTapUp: (details) => showButtons.value = !showButtons.value,
+            isZoomedOut.value = value == PhotoViewScaleState.zoomedOut ||
-          child: PhotoView(
+                value == PhotoViewScaleState.initial;
-            scaleStateChangedCallback: (value) {
+          },
-              isZoomedOut.value = value == PhotoViewScaleState.zoomedOut ||
+          minScale: PhotoViewComputedScale.contained,
-                  value == PhotoViewScaleState.initial;
+          initialScale: PhotoViewComputedScale.contained,
-            },
+          imageProvider: CachedNetworkImageProvider(url),
-            minScale: PhotoViewComputedScale.contained,
+          heroAttributes: PhotoViewHeroAttributes(tag: url),
-            initialScale: PhotoViewComputedScale.contained,
+          loadingBuilder: (context, event) =>
-            imageProvider: CachedNetworkImageProvider(url),
+              Center(child: CircularProgressIndicator()),
-            heroAttributes: PhotoViewHeroAttributes(tag: url),
-            loadingBuilder: (context, event) =>
-                Center(child: CircularProgressIndicator()),
-          ),
         ),
       ),
     );