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仿真翻页 参考了
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https://github.com/fluttercommunity/page_turn
fluttercommunity/page_turn#15
fluttercommunity/page_turn#12
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@mabDc
mabDc committed Mar 20, 2021
1 parent e7ee4e1 commit d3e91cd
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265 changes: 265 additions & 0 deletions lib/page_turn.dart
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import 'dart:math';

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'package:page_turn/src/builders/index.dart';

import 'text_composition.dart';

class PageTurn extends StatefulWidget {
PageTurn({
Key? key,
this.duration = const Duration(milliseconds: 300),
this.cuton = 8,
this.cutoff = 92,
this.backgroundColor = const Color(0xFFFFFFCC),
required this.textComposition,
this.initialIndex = 0,
this.lastPage = const Center(
child: const Text("已经是最后一页"),
),
this.showDragCutoff = true,
}) : super(key: key);

final Color backgroundColor;
final TextComposition textComposition;
final Duration duration;
final int initialIndex;
final Widget? lastPage;
final bool showDragCutoff;
final int cutoff;
final int cuton;

@override
PageTurnState createState() => PageTurnState();
}

class PageTurnState extends State<PageTurn> with TickerProviderStateMixin {
int pageNumber = 0;
List<Widget> pages = [];

List<AnimationController> _controllers = [];
bool? _isForward;

@override
void didUpdateWidget(PageTurn oldWidget) {
if (oldWidget.textComposition != widget.textComposition) {
_setUp();
}
if (oldWidget.duration != widget.duration) {
_setUp();
}
if (oldWidget.backgroundColor != widget.backgroundColor) {
_setUp();
}
super.didUpdateWidget(oldWidget);
}

@override
void dispose() {
_controllers.forEach((c) => c.dispose());
super.dispose();
}

@override
void initState() {
super.initState();
_setUp();
}

static const BLANK_PAGE = const Center();
void _setUp() {
_controllers.clear();
pages.clear();
for (var i = 0; i < widget.textComposition.pageCount; i++) {
final _controller = AnimationController(
value: 1,
duration: widget.duration,
vsync: this,
);
_controllers.add(_controller);
final _child = Container(
child: PageTurnWidget(
backgroundColor: widget.backgroundColor,
amount: _controllers[i],
child: widget.textComposition.getPageWidget(pageIndex: i),
),
);
pages.add(_child);
}
pages = pages.reversed.toList();
pageNumber = widget.initialIndex;
}

bool get _isLastPage => pages.length - 1 == pageNumber;

bool get _isFirstPage => pageNumber == 0;

void _turnPage(DragUpdateDetails details, BoxConstraints dimens) {
final _ratio = details.delta.dx / dimens.maxWidth;
if (_isForward == null) {
if (details.delta.dx > 0) {
_isForward = false;
} else {
_isForward = true;
}
}
if (_isForward! || pageNumber == 0) {
_controllers[pageNumber].value += _ratio;
} else {
_controllers[pageNumber - 1].value += _ratio;
}
}

Future<void> _onDragFinish() async {
if (_isForward != null) {
if (_isForward!) {
if (!_isLastPage &&
_controllers[pageNumber].value <= (widget.cutoff / 100 + 0.03)) {
await nextPage();
} else {
await _controllers[pageNumber].forward();
}
} else {
if (!_isFirstPage &&
_controllers[pageNumber - 1].value >= (widget.cuton / 100 + 0.05)) {
await previousPage();
} else {
if (_isFirstPage) {
await _controllers[pageNumber].forward();
} else {
await _controllers[pageNumber - 1].reverse();
}
}
}
}
_isForward = null;
}

Future<void> nextPage() async {
_controllers[pageNumber].reverse();
if (mounted) {
setState(() {
pageNumber++;
});
}
}

Future<void> previousPage() async {
if (pageNumber > 0) {
await _controllers[pageNumber - 1].forward();
if (mounted)
setState(() {
pageNumber--;
});
}
}

Future<void> goToPage(int index) async {
if (mounted)
setState(() {
pageNumber = index;
});
for (var i = 0; i < _controllers.length; i++) {
if (i == index) {
_controllers[i].forward();
} else if (i < index) {
_controllers[i].reverse();
} else {
if (_controllers[i].status == AnimationStatus.reverse)
_controllers[i].value = 1;
}
}
}

@override
Widget build(BuildContext context) {
int i = 0;
return Material(
child: LayoutBuilder(
builder: (context, dimens) => GestureDetector(
behavior: HitTestBehavior.opaque,
onHorizontalDragCancel: () => _isForward = null,
onHorizontalDragUpdate: (details) => _turnPage(details, dimens),
onHorizontalDragEnd: (details) => _onDragFinish(),
child: Stack(
fit: StackFit.expand,
children: <Widget>[
if (widget.lastPage != null) widget.lastPage!,
...pages.map((p) {
i++;
final pn = pages.length - pageNumber;
final ret =
Offstage(offstage: !(i >= pn - 1 && i <= pn + 1), child: p);
return ret;
}).toList(),
Positioned.fill(
child: Flex(
direction: Axis.horizontal,
children: <Widget>[
Flexible(
flex: widget.cuton,
child: Container(
color:
pageNumber < 3 ? Colors.green.withAlpha(100) : null,
child: pageNumber < 3
? Center(
child: Text("手势上一页",
style: TextStyle(fontSize: 25)))
: null,
),
),
Flexible(
flex: 50 - widget.cuton,
child: Container(
color:
pageNumber < 3 ? Colors.blue.withAlpha(100) : null,
child: GestureDetector(
behavior: HitTestBehavior.opaque,
onTap: _isFirstPage ? null : previousPage,
child: pageNumber < 3
? Center(
child: Text("点击上一页",
style: TextStyle(fontSize: 25)))
: null,
),
),
),
Flexible(
flex: widget.cutoff - 50,
child: Container(
color:
pageNumber < 3 ? Colors.red.withAlpha(100) : null,
child: GestureDetector(
behavior: HitTestBehavior.opaque,
onTap: _isLastPage ? null : nextPage,
child: pageNumber < 3
? Center(
child: Text("点击下一页",
style: TextStyle(fontSize: 25)))
: null,
),
),
),
Flexible(
flex: 100 - widget.cutoff,
child: Container(
color:
pageNumber < 3 ? Colors.pink.withAlpha(100) : null,
child: pageNumber < 3
? Center(
child: Text("手势下一页",
style: TextStyle(fontSize: 25)))
: null,
),
),
],
),
),
],
),
),
),
);
}
}

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