Snackbar displays at top (#820)

- Closes https://github.com/inventree/inventree-app/issues/626

lib/widget/snacks.dart

@@ -1,3 +1,5 @@
+import "dart:async";
+
 import "package:flutter/material.dart";
 import "package:flutter_tabler_icons/flutter_tabler_icons.dart";
 import "package:one_context/one_context.dart";
@@ -5,8 +7,10 @@ import "package:one_context/one_context.dart";
 import "package:inventree/helpers.dart";
 import "package:inventree/l10.dart";
 
+OverlayEntry? _currentSnackOverlay;
+
 /*
- * Display a configurable 'snackbar' at the bottom of the screen
+ * Display a configurable 'snackbar' at the top of the screen
  */
 void showSnackIcon(
   String text, {
@@ -19,23 +23,21 @@ void showSnackIcon(
 
   // Escape quickly if we do not have context
   if (!hasContext()) {
-    // Debug message for unit testing
     return;
   }
 
   BuildContext? context = OneContext().context;
+  if (context == null) return;
 
-  if (context != null) {
-    ScaffoldMessenger.of(context).hideCurrentSnackBar();
-  }
+  // Dismiss any currently visible snack immediately
+  _currentSnackOverlay?.remove();
+  _currentSnackOverlay = null;
 
   Color backgroundColor = Colors.deepOrange;
 
-  // Make some selections based on the "success" value
   if (success != null && success == true) {
     backgroundColor = Colors.lightGreen;
 
-    // Select an icon if we do not have an action
     if (icon == null && onAction == null) {
       icon = TablerIcons.circle_check;
     }
@@ -47,35 +49,157 @@ void showSnackIcon(
     }
   }
 
-  String _action = actionText ?? L10().details;
+  final String actionLabel = actionText ?? L10().details;
+  final Duration duration = Duration(seconds: onAction == null ? 5 : 10);
 
-  List<Widget> childs = [Text(text), Spacer()];
+  late OverlayEntry entry;
+  entry = OverlayEntry(
+    builder: (ctx) => _TopSnackBar(
+      text: text,
+      icon: icon,
+      backgroundColor: backgroundColor,
+      onAction: onAction,
+      actionText: actionLabel,
+      duration: duration,
+      onDismiss: () {
+        entry.remove();
+        if (_currentSnackOverlay == entry) {
+          _currentSnackOverlay = null;
+        }
+      },
+    ),
+  );
 
-  if (icon != null) {
-    childs.add(Icon(icon));
+  _currentSnackOverlay = entry;
+  Overlay.of(context).insert(entry);
 }
 
-  OneContext().showSnackBar(
-    builder: (context) => SnackBar(
-      content: GestureDetector(
-        child: Row(children: childs),
-        onTap: () {
-          ScaffoldMessenger.of(context!).hideCurrentSnackBar();
-        },
+class _TopSnackBar extends StatefulWidget {
+  const _TopSnackBar({
+    required this.text,
+    required this.backgroundColor,
+    required this.duration,
+    required this.onDismiss,
+    this.icon,
+    this.onAction,
+    this.actionText,
+  });
+
+  final String text;
+  final IconData? icon;
+  final Color backgroundColor;
+  final Function()? onAction;
+  final String? actionText;
+  final Duration duration;
+  final VoidCallback onDismiss;
+
+  @override
+  _TopSnackBarState createState() => _TopSnackBarState();
+}
+
+class _TopSnackBarState extends State<_TopSnackBar>
+    with SingleTickerProviderStateMixin {
+  late final AnimationController _controller;
+  late final Animation<Offset> _slideAnimation;
+  Timer? _timer;
+  bool _dismissed = false;
+
+  @override
+  void initState() {
+    super.initState();
+
+    _controller = AnimationController(
+      vsync: this,
+      duration: const Duration(milliseconds: 300),
+    );
+
+    _slideAnimation = Tween<Offset>(
+      begin: const Offset(0, -1),
+      end: Offset.zero,
+    ).animate(CurvedAnimation(parent: _controller, curve: Curves.easeOut));
+
+    _controller.forward();
+    _timer = Timer(widget.duration, _dismiss);
+  }
+
+  @override
+  void dispose() {
+    _timer?.cancel();
+    _controller.dispose();
+    super.dispose();
+  }
+
+  void _dismiss() {
+    if (_dismissed) return;
+    _dismissed = true;
+    _timer?.cancel();
+    _timer = null;
+    _controller.reverse().then((_) {
+      if (mounted) widget.onDismiss();
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Positioned(
+      top: 0,
+      left: 0,
+      right: 0,
+      child: SlideTransition(
+        position: _slideAnimation,
+        child: Material(
+          color: Colors.transparent,
+          child: ColoredBox(
+            color: widget.backgroundColor,
+            child: SafeArea(
+              bottom: false,
+              child: Padding(
+                padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 4),
+                child: Row(
+                  children: [
+                    Expanded(
+                      child: GestureDetector(
+                        onTap: _dismiss,
+                        behavior: HitTestBehavior.opaque,
+                        child: Row(
+                          children: [
+                            Expanded(
+                              child: Text(
+                                widget.text,
+                                style: const TextStyle(color: Colors.white),
                               ),
-      backgroundColor: backgroundColor,
-      showCloseIcon: true,
-      action: onAction == null
-          ? null
-          : SnackBarAction(
-              label: _action,
+                            ),
+                            if (widget.icon != null)
+                              Padding(
+                                padding: const EdgeInsets.only(left: 8),
+                                child: Icon(widget.icon, color: Colors.white),
+                              ),
+                          ],
+                        ),
+                      ),
+                    ),
+                    if (widget.onAction != null)
+                      TextButton(
                         onPressed: () {
-                // Immediately dismiss the notification
-                ScaffoldMessenger.of(context!).hideCurrentSnackBar();
-                onAction();
+                          _dismiss();
+                          widget.onAction!();
                         },
+                        child: Text(
+                          widget.actionText ?? "",
+                          style: const TextStyle(color: Colors.white),
+                        ),
+                      ),
+                    IconButton(
+                      icon: const Icon(Icons.close, color: Colors.white),
+                      onPressed: _dismiss,
+                    ),
+                  ],
+                ),
+              ),
+            ),
+          ),
         ),
-      duration: Duration(seconds: onAction == null ? 5 : 10),
       ),
     );
   }
+}