42 lines
1.0 KiB
Dart
42 lines
1.0 KiB
Dart
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import 'dart:math' show max, min;
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import 'package:flutter/material.dart';
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import 'package:flutter_hooks/flutter_hooks.dart';
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/// Makes the child reveal itself after given distance
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class RevealAfterScroll extends HookWidget {
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final Widget child;
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/// distance after which [child] should appear
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final int after;
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final int transition;
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final ScrollController scrollController;
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final bool fade;
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const RevealAfterScroll({
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@required this.scrollController,
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@required this.child,
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@required this.after,
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this.transition = 15,
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this.fade = false,
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}) : assert(scrollController != null),
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assert(child != null),
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assert(after != null);
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@override
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Widget build(BuildContext context) {
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useListenable(scrollController);
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final scroll = scrollController.position.pixels;
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return Opacity(
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opacity:
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fade ? max(0, min(transition, scroll - after + 20)) / transition : 1,
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child: Transform.translate(
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offset: Offset(0, max(0, after - scroll)),
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child: child,
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),
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);
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}
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}
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