new animation added

packages/simplex_app/lib/animations/entrance_fader.dart

@@ -0,0 +1,70 @@
+import 'package:flutter/material.dart';
+
+class EntranceFader extends StatefulWidget {
+  /// Child to be animated on entrance
+  final Widget? child;
+
+  /// Delay after which the animation will start
+  final Duration delay;
+
+  /// Duration of entrance animation
+  final Duration duration;
+
+  /// Starting point from which the widget will fade to its default position
+  final Offset offset;
+
+  const EntranceFader({
+    Key? key,
+    this.child,
+    this.delay = const Duration(milliseconds: 0),
+    this.duration = const Duration(milliseconds: 400),
+    this.offset = const Offset(0.0, 32.0),
+  }) : super(key: key);
+
+  @override
+  EntranceFaderState createState() {
+    return EntranceFaderState();
+  }
+}
+
+class EntranceFaderState extends State<EntranceFader>
+    with SingleTickerProviderStateMixin {
+  AnimationController? _controller;
+  Animation? _dxAnimation;
+  Animation? _dyAnimation;
+
+  @override
+  void initState() {
+    super.initState();
+    _controller = AnimationController(vsync: this, duration: widget.duration);
+    _dxAnimation =
+        Tween(begin: widget.offset.dx, end: 0.0).animate(_controller!);
+    _dyAnimation =
+        Tween(begin: widget.offset.dy, end: 0.0).animate(_controller!);
+    Future.delayed(widget.delay, () {
+      if (mounted) {
+        _controller!.forward();
+      }
+    });
+  }
+
+  @override
+  void dispose() {
+    _controller!.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return AnimatedBuilder(
+      animation: _controller!,
+      builder: (context, child) => Opacity(
+        opacity: _controller!.value,
+        child: Transform.translate(
+          offset: Offset(_dxAnimation!.value, _dyAnimation!.value),
+          child: widget.child,
+        ),
+      ),
+    );
+  }
+}