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84 changes: 56 additions & 28 deletions lib/overlapping_panels.dart
Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ import 'package:flutter/material.dart';
import 'dart:core';

const double bleedWidth = 20;
const double minPixelsPerSecond = 240;

/// Display sections
enum RevealSide { left, right, main }
Expand All @@ -30,12 +31,11 @@ class OverlappingPanels extends StatefulWidget {
final ValueChanged<RevealSide>? onSideChange;

const OverlappingPanels({this.left,
required this.main,
this.right,
this.restWidth = 40,
this.onSideChange,
Key? key})
: super(key: key);
required this.main,
this.right,
this.restWidth = 40,
this.onSideChange,
super.key});

static OverlappingPanelsState? of(BuildContext context) {
return context.findAncestorStateOfType<OverlappingPanelsState>();
Expand All @@ -51,19 +51,20 @@ class OverlappingPanelsState extends State<OverlappingPanels>
with TickerProviderStateMixin {
AnimationController? controller;
double translate = 0;
double lastTranslate = 0;

double _calculateGoal(double width, int multiplier) {
return (multiplier * width) + (-multiplier * widget.restWidth);
}

void _onApplyTranslation() {
void _onApplyTranslation(Offset pixelsPerSecond) {
final mediaWidth = MediaQuery
.of(context)
.size
.width;

final animationController = AnimationController(
vsync: this, duration: const Duration(milliseconds: 200));
vsync: this, duration: const Duration(milliseconds: 160));

animationController.addStatusListener((status) {
if (status == AnimationStatus.completed) {
Expand All @@ -76,28 +77,39 @@ class OverlappingPanelsState extends State<OverlappingPanels>
}
});

if (translate.abs() >= mediaWidth / 2) {
double goal;
if (pixelsPerSecond.dx.abs() > minPixelsPerSecond) {
final multiplier = (translate > lastTranslate
? lastTranslate < 0
? 0
: 1
: lastTranslate > 0
? 0
: -1);
goal = _calculateGoal(mediaWidth, multiplier);
} else if (translate.abs() >= mediaWidth / 2) {
final multiplier = (translate > 0 ? 1 : -1);
final goal = _calculateGoal(mediaWidth, multiplier);
final Tween<double> tween = Tween(begin: translate, end: goal);
goal = _calculateGoal(mediaWidth, multiplier);
} else {
goal = 0;
}

final animation = tween.animate(animationController);
if (widget.left == null && goal > 0) goal = 0;
if (widget.right == null && goal < 0) goal = 0;

animation.addListener(() {
setState(() {
translate = animation.value;
});
});
} else {
final animation =
Tween<double>(begin: translate, end: 0).animate(animationController);
final Tween<double> tween = Tween<double>(begin: translate, end: goal);

animation.addListener(() {
setState(() {
translate = animation.value;
});
final animation = tween.animate(CurvedAnimation(
parent: animationController,
curve: Curves.fastOutSlowIn,
));

animation.addListener(() {
setState(() {
translate = animation.value;
lastTranslate = animation.value;
});
}
});

animationController.forward();
}
Expand All @@ -121,13 +133,13 @@ class OverlappingPanelsState extends State<OverlappingPanels>

animationController.addStatusListener((status) {
if (status == AnimationStatus.completed) {
_onApplyTranslation();
_onApplyTranslation(Offset.zero);
animationController.dispose();
}
});

final animation =
Tween<double>(begin: translate, end: goal).animate(animationController);
Tween<double>(begin: translate, end: goal).animate(animationController);

animation.addListener(() {
setState(() {
Expand All @@ -148,6 +160,22 @@ class OverlappingPanelsState extends State<OverlappingPanels>
});
}

@override
void didUpdateWidget(covariant OverlappingPanels oldWidget) {
super.didUpdateWidget(oldWidget);
if (widget.left == null) {
setState(() {
translate = 0;
});
} else {
final mediaWidth = MediaQuery.of(context).size.width;
setState(() {
translate = _calculateGoal(mediaWidth, 1);
});
}
_onApplyTranslation(Offset.zero);
}

@override
Widget build(BuildContext context) {
return Stack(children: [
Expand All @@ -169,7 +197,7 @@ class OverlappingPanelsState extends State<OverlappingPanels>
onTranslate(details.delta.dx);
},
onHorizontalDragEnd: (details) {
_onApplyTranslation();
_onApplyTranslation(details.velocity.pixelsPerSecond);
},
),
]);
Expand Down