Flutter web ignore resize - flutter

I would like to make my web app does not resize/responsive when the screen become smaller. For example when i decrease my browser size, instead of its adapting to the width and height, i want the web app to ignore it and user can just scroll up, down, left and right to view the web.

I suggest you to use a LayoutBuilder and eventually add a SingleChildScrollView when the size becomes lower than your app expects.
This MinSize widget accomplishes it.
/// Starts scrolling [child] vertically and horizontally when the widget sizes
/// reaches below [minWidth] or [minHeight]
class MinSize extends StatefulWidget {
const MinSize({
Key? key,
this.minWidth,
this.minHeight,
required this.child,
}) : super(key: key);
final Widget child;
final double? minWidth;
final double? minHeight;
#override
State<MinSize> createState() => _MinSizeState();
}
class _MinSizeState extends State<MinSize> {
late final _verticalController = ScrollController();
late final _horizontalController = ScrollController();
#override
Widget build(BuildContext context) {
return LayoutBuilder(
builder: (context, constraints) {
final shouldScrollVertical = widget.minHeight != null &&
constraints.maxHeight <= widget.minHeight!;
final contentHeight =
shouldScrollVertical ? widget.minHeight : constraints.maxHeight;
final verticalPhysics = shouldScrollVertical
? const AlwaysScrollableScrollPhysics()
: const NeverScrollableScrollPhysics();
final shouldScrollHorizontal =
widget.minWidth != null && constraints.maxWidth <= widget.minWidth!;
final contentWidth =
shouldScrollHorizontal ? widget.minWidth : constraints.maxWidth;
final horizontalPhysics = shouldScrollHorizontal
? const AlwaysScrollableScrollPhysics()
: const NeverScrollableScrollPhysics();
return Scrollbar(
controller: _verticalController,
thumbVisibility: shouldScrollVertical,
child: SingleChildScrollView(
controller: _verticalController,
scrollDirection: Axis.vertical,
physics: verticalPhysics,
child: Scrollbar(
interactive: true,
controller: _horizontalController,
thumbVisibility: shouldScrollHorizontal,
child: SingleChildScrollView(
controller: _horizontalController,
scrollDirection: Axis.horizontal,
physics: horizontalPhysics,
child: UnconstrainedBox(
child: SizedBox(
height: contentHeight,
width: contentWidth,
child: widget.child,
),
),
),
),
),
);
},
);
}
}
Alternatively, try the InteractiveViewer to freely move the content in the app window.

Use a SizedBox with a fixed height/width property

Related

How can I achieve "child of a widget which is inside a scroll widget acting like sticky header" in Flutter?

I'm trying to find a way to implement a functionality in which, in a horizontally scrollable list, there are widgets that I will call P, (which are denoted as P1, P2 and P3 in the diagram) and their children C, (which are denoted as C1, C2 and C3). As the user scrolls the list horizontally, I want C's inside P's to act like sticky headers, until they reach the boundary of their parent.
I'm sorry if the description & diagram is not enough, I will try to clarify anything unclear.
Diagram of the problem
As I'm thinking of a way to implement this, I can't seem to find a plausible solution. Also if there is a package that can help with this issue, I would really appreciate any suggestions.
I am not sure about your picture, but maybe this is do you want?
our tools :
BuildOwners -> to measure size of the widget before rebuild,
NotificationListeners -> to trigger rebuild based on ScrollNotification. i use stateful Widget, but you can tweak it into ValueNotifier and Build the Sticker with ValueListenableBuilder instead.
ListView.Builder -> actually you can replace this with any kind of Scrollable, we only need to listen scroll event.
how its work?
its simple :
we need to know the P dx Offset, check if C offset small than P, then use that value to adjust x Positioned of C in Stack. and clamp it with max value (P.width)
double _calculateStickerXPosition(
{required double px, required double cx, required double cw}) {
if (cx < px) {
return widget.stickerHorizontalPadding + (px - cx).clamp(0.0, cw - (widget.stickerHorizontalPadding*2));
}
return widget.stickerHorizontalPadding;
}
full code :
main.dart :
import 'dart:ui';
import 'package:flutter/material.dart';
import 'scrollable_sticker.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return MaterialApp(
// i use chrome to test it, so igrone this
scrollBehavior: const MaterialScrollBehavior().copyWith(
dragDevices: {
PointerDeviceKind.mouse,
PointerDeviceKind.touch,
PointerDeviceKind.stylus,
PointerDeviceKind.unknown
},
),
home: const MyWidget(),
);
}
}
class MyWidget extends StatelessWidget {
const MyWidget({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
body: Padding(
padding: const EdgeInsets.symmetric(vertical: 20.0),
child: ScrollableSticker(
children: List.generate(10, (index) => Container(
width: 500,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(10.0),
border: Border.all(color: Colors.orange)),
child: const Padding(
padding: EdgeInsets.symmetric(vertical: 50.0, horizontal: 50.0),
child: Text(
"P1",
textDirection: TextDirection.ltr,
),
),
)),
stickerBuilder: (index) => Container(
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(10), color: Colors.red),
child: Padding(
padding: const EdgeInsets.all(10.0),
child: Text(
'C$index',
),
),
)),
),
);
}
}
scrollable_sticker.dart :
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
class ScrollableSticker extends StatefulWidget {
final List<Widget> children;
final Widget Function(int index) stickerBuilder;
final double stickerHorizontalPadding;
const ScrollableSticker(
{Key? key,
required this.children,
required this.stickerBuilder,
this.stickerHorizontalPadding = 10.0})
: super(key: key);
#override
State<ScrollableSticker> createState() => _ScrollableStickerState();
}
class _ScrollableStickerState extends State<ScrollableSticker> {
late List<GlobalKey> _keys;
late GlobalKey _parentKey;
#override
void initState() {
super.initState();
_keys = List.generate(widget.children.length, (index) => GlobalKey());
_parentKey = GlobalKey();
}
#override
Widget build(BuildContext context) {
return NotificationListener<ScrollNotification>(
onNotification: (sc) {
setState(() {});
return true;
},
child: ListView.builder(
key: _parentKey,
scrollDirection: Axis.horizontal,
itemCount: widget.children.length,
itemBuilder: (context, index) {
final itemSize = measureWidget(Directionality(
textDirection: TextDirection.ltr, child: widget.children[index]));
final stickerSize = measureWidget(Directionality(
textDirection: TextDirection.ltr,
child: widget.stickerBuilder(index)));
final BuildContext? itemContext = _keys[index].currentContext;
double x = widget.stickerHorizontalPadding;
if (itemContext != null) {
final pcontext = _parentKey.currentContext;
Offset? pOffset;
if (pcontext != null) {
RenderObject? obj = pcontext.findRenderObject();
if (obj != null) {
final prb = obj as RenderBox;
pOffset = prb.localToGlobal(Offset.zero);
}
}
final obj = itemContext.findRenderObject();
if (obj != null) {
final rb = obj as RenderBox;
final cx = rb.localToGlobal(pOffset ?? Offset.zero).dx;
x = _calculateStickerXPosition(
px: pOffset != null ? pOffset.dx : 0.0,
cx: cx,
cw: (itemSize.width - stickerSize.width));
}
}
return SizedBox(
key: _keys[index],
height: itemSize.height,
width: itemSize.width,
child: Stack(
children: [
widget.children[index],
Positioned(
top: itemSize.height / 2,
left: x,
child: FractionalTranslation(
translation: const Offset(0.0, -0.5),
child: widget.stickerBuilder(index)))
],
),
);
},
),
);
}
double _calculateStickerXPosition(
{required double px, required double cx, required double cw}) {
if (cx < px) {
return widget.stickerHorizontalPadding +
(px - cx).clamp(0.0, cw - (widget.stickerHorizontalPadding * 2));
}
return widget.stickerHorizontalPadding;
}
}
Size measureWidget(Widget widget) {
final PipelineOwner pipelineOwner = PipelineOwner();
final MeasurementView rootView = pipelineOwner.rootNode = MeasurementView();
final BuildOwner buildOwner = BuildOwner(focusManager: FocusManager());
final RenderObjectToWidgetElement<RenderBox> element =
RenderObjectToWidgetAdapter<RenderBox>(
container: rootView,
debugShortDescription: '[root]',
child: widget,
).attachToRenderTree(buildOwner);
try {
rootView.scheduleInitialLayout();
pipelineOwner.flushLayout();
return rootView.size;
} finally {
// Clean up.
element.update(RenderObjectToWidgetAdapter<RenderBox>(container: rootView));
buildOwner.finalizeTree();
}
}
class MeasurementView extends RenderBox
with RenderObjectWithChildMixin<RenderBox> {
#override
void performLayout() {
assert(child != null);
child!.layout(const BoxConstraints(), parentUsesSize: true);
size = child!.size;
}
#override
void debugAssertDoesMeetConstraints() => true;
}
you could try to use c padding dynamically
padding: EdgeInsets.only(left: 0.1 * [index], right: 1 * [index])
for example, I hope it helps.

Implementing custom horizontal scroll of listview of items like Louis Vuitton app

Recently I have downloaded the Louis Vuitton App. I found a strange type of horizontal scroll of product items in listview. I tried card_swiper package but couldnot get through it. How can I achieve such scroll as in gif below?
the trick here is to use a stack and:
Use a page view to display every element except the first one
Use a left aligned FractionallySizedBox which displays the first item and grows with the first item offset
It took me a few tries but the result is very satisfying, I'll let you add the bags but here you go with colored boxes ;) :
import 'dart:math';
import 'package:flutter/material.dart';
void main() {
runApp(MaterialApp(home: FunList()));
}
class FunList extends StatefulWidget {
#override
State<FunList> createState() => _FunListState();
}
class _FunListState extends State<FunList> {
/// The colors of the items in the list
final _itemsColors = List.generate(
100,
(index) => Color((Random().nextDouble() * 0xFFFFFF).toInt()).withOpacity(1.0),
);
/// The current page of the page view
double _page = 0;
/// The index of the leftmost element of the list to be displayed
int get _firstItemIndex => _page.toInt();
/// The offset of the leftmost element of the list to be displayed
double get _firstItemOffset => _controller.hasClients ? 1 - (_page % 1) : 1;
/// Controller to get the current position of the page view
final _controller = PageController(
viewportFraction: 0.25,
);
/// The width of a single item
late final _itemWidth = MediaQuery.of(context).size.width * _controller.viewportFraction;
#override
void initState() {
super.initState();
_controller.addListener(() => setState(() {
_page = _controller.page!;
}));
}
#override
void dispose() {
_controller.dispose();
super.dispose();
}
#override
Widget build(BuildContext context) {
return Center(
child: Stack(
children: [
Positioned.fill(
child: Align(
alignment: Alignment.centerLeft,
child: SizedBox(
width: _itemWidth,
child: FractionallySizedBox(
widthFactor: _firstItemOffset,
heightFactor: _firstItemOffset,
child: PageViewItem(color: _itemsColors[_firstItemIndex]),
),
),
),
),
SizedBox(
height: 200,
child: PageView.builder(
padEnds: false,
controller: _controller,
itemBuilder: (context, index) {
return Opacity(
opacity: index <= _firstItemIndex ? 0 : 1,
child: PageViewItem(color: _itemsColors[index]),
);
},
itemCount: _itemsColors.length,
),
),
],
),
);
}
}
class PageViewItem extends StatelessWidget {
final Color color;
const PageViewItem({
Key? key,
required this.color,
}) : super(key: key);
#override
Widget build(BuildContext context) {
return Container(
margin: EdgeInsets.all(10),
color: color,
);
}
}

How to programmatically Collapse or Expand SliverPresistentHeader [custom floating app bar]

I am trying to programmatically collapse or expand the SliverPresistantHeader with the reference from shrinkOffset value. I have looked everywhere to find how to implement this feature, but I couldn't find any solution (so here I am asking).
Here my code for my custom SliverPresistantHeaderDelegate:
import 'package:bom/constants/constants.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
class BomAppHeader implements SliverPersistentHeaderDelegate {
BomAppHeader({
this.expandedHeight,
this.title,
this.body,
#required this.notificationShade,
});
final double notificationShade;
final double expandedHeight;
final Widget title;
final Widget body;
#override
double get maxExtent {
if (expandedHeight == null || expandedHeight < kToolbarHeight) {
return minExtent;
} else {
return notificationShade + expandedHeight;
}
}
#override
double get minExtent {
return title == null
? notificationShade
: notificationShade + kToolbarHeight;
}
double bodyOpacity(double shrinkOffset) {
return max(0.0, 1 - (shrinkOffset / (maxExtent - minExtent)));
}
#override
Widget build(
BuildContext context, double shrinkOffset, bool overlapsContent) {
// print(max(0.0, 1 - (shrinkOffset / (maxExtent - minExtent))));
return Stack(
fit: StackFit.expand,
children: [
Container(
decoration: kAppBarDecoration,
),
Opacity(
opacity: bodyOpacity(shrinkOffset),
child: Container(
height: maxExtent > minExtent ? double.infinity : 0.0,
margin: title == null
? EdgeInsets.only(top: notificationShade + 2)
: EdgeInsets.only(
top: notificationShade, bottom: kToolbarHeight),
padding: EdgeInsets.all(8.0),
child: body,
),
),
Column(mainAxisAlignment: MainAxisAlignment.spaceBetween, children: [
SizedBox(
height: notificationShade,
),
Container(
height: title == null ? 0.0 : kToolbarHeight,
padding: EdgeInsets.all(5.0),
child: title,
),
]),
],
);
}
double titleOpacity(double shrinkOffset) {
// simple formula: fade out text as soon as shrinkOffset > 0
return 1.0 - max(0.0, shrinkOffset) / maxExtent;
// more complex formula: starts fading out text when shrinkOffset > minExtent
//return 1.0 - max(0.0, (shrinkOffset - minExtent)) / (maxExtent - minExtent);
}
#override
bool shouldRebuild(covariant SliverPersistentHeaderDelegate oldDelegate) {
return true;
}
#override
// TODO: implement showOnScreenConfiguration
PersistentHeaderShowOnScreenConfiguration get showOnScreenConfiguration =>
null;
#override
// TODO: implement snapConfiguration
FloatingHeaderSnapConfiguration get snapConfiguration => null;
#override
// TODO: implement stretchConfiguration
OverScrollHeaderStretchConfiguration get stretchConfiguration => null;
#override
// TODO: implement vsync
TickerProvider get vsync => null;
}
So far I didn't find any solution for implementing this, still surfing the web.
As flutter is open-source and we have access to their built-in codes (I recently look into each widget code deeply to learn how each thing works ;-)), I found the snap functionality is the one I am looking for from the flutter documentation. So I looked into SliverAppBar and how snap implemented in it. Just copied out the things I needed and all works as expected now.
[if anyone need my code, ask me out. I suppose nobody interested or looked into this question, lol, better say, mine was a dump question]
Add a scroll controller to your 'Custom Scroll View'
ScrollController _scrollController;
Widget build(BuildContext context) {
_scrollController = ScrollController();
return Scaffold(
body: CustomScrollView( shrinkWrap: true, controller: _scrollController,
physics: BouncingScrollPhysics(),
slivers: <Widget>[
SliverAppBar(
pinned: false,
:
:
:
onPressed: () {// Scroll to top when on click => Expand
_scrollController.animateTo(
_scrollController.position.minScrollExtent,
duration:Duration(milliseconds:1300),
curve: Curves.decelerate,);
},
onPressed: () {// Scroll to bottom when on click => Collapse
scrollController.animateTo(
scrollController.position.maxScrollExtent,
duration: Duration(milliseconds: 1300),
curve: Curves.decelerate,
);
},

Flutter - Using Dismissible on a PageView creates an ugly animation

with the following example code, is get a very ugly animation.
I would even say, it's no animation at all.
The next Page will just appear after the setstate is called.
How can I create a smooth delete animation using PageView?
If it is not possible via PageView, is there any alternative, that has the "snapping cards" feature?
Here is my code:
class SwipeScreen extends StatefulWidget {
const SwipeScreen({Key key}) : super(key: key);
static const routeName = '/swipe';
#override
_SwipeScreenState createState() => _SwipeScreenState();
}
class _SwipeScreenState extends State<SwipeScreen> {
List<String> content = ['one', 'two', 'three', 'four', 'five'];
#override
Widget build(BuildContext context) {
return Scaffold(
body: PageView.builder(
scrollDirection: Axis.vertical,
itemCount: content.length,
controller: PageController(viewportFraction: 0.8),
itemBuilder: (context, index) {
return Dismissible(
key: ValueKey(content[index]),
child: Card(
child: Container(
height: MediaQuery.of(context).size.height * 0.8,
child: Text('test'),
),
),
onDismissed: (direction) {
setState(() {
content = List.from(content)..removeAt(index);
});
},
);
},
),
);
}
}
Replacing PageView.builder() with ListView.builder() will create a smoother animation.
Hopefully this is what you're looking for!
Unfortunately, the PageView widget is not intended to be used with the Dismissible widget as the animation when the dismiss is complete is not implemented.
You can still change your PageView to a ListView and set a physics to PageScrollPhysics() to get the animation on dismiss but you will probably encounter some other issues on Widget sizes

How to get height of a Widget?

I don't understand how LayoutBuilder is used to get the height of a Widget.
I need to display the list of Widgets and get their height so I can compute some special scroll effects. I am developing a package and other developers provide widget (I don't control them). I read that LayoutBuilder can be used to get height.
In very simple case, I tried to wrap Widget in LayoutBuilder.builder and put it in the Stack, but I always get minHeight 0.0, and maxHeight INFINITY. Am I misusing the LayoutBuilder?
EDIT: It seems that LayoutBuilder is a no go. I found the CustomSingleChildLayout which is almost a solution.
I extended that delegate, and I was able to get the height of widget in getPositionForChild(Size size, Size childSize) method. BUT, the first method that is called is Size getSize(BoxConstraints constraints) and as constraints, I get 0 to INFINITY because I'm laying these CustomSingleChildLayouts in a ListView.
My problem is that SingleChildLayoutDelegate getSize operates like it needs to return the height of a view. I don't know the height of a child at that moment. I can only return constraints.smallest (which is 0, the height is 0), or constraints.biggest which is infinity and crashes the app.
In the docs it even says:
...but the size of the parent cannot depend on the size of the child.
And that's a weird limitation.
To get the size/position of a widget on screen, you can use GlobalKey to get its BuildContext to then find the RenderBox of that specific widget, which will contain its global position and rendered size.
Just one thing to be careful of: That context may not exist if the widget is not rendered. Which can cause a problem with ListView as widgets are rendered only if they are potentially visible.
Another problem is that you can't get a widget's RenderBox during build call as the widget hasn't been rendered yet.
But what if I need to get the size during the build! What can I do?
There's one cool widget that can help: Overlay and its OverlayEntry.
They are used to display widgets on top of everything else (similar to stack).
But the coolest thing is that they are on a different build flow; they are built after regular widgets.
That have one super cool implication: OverlayEntry can have a size that depends on widgets of the actual widget tree.
Okay. But don't OverlayEntry requires to be rebuilt manually?
Yes, they do. But there's another thing to be aware of: ScrollController, passed to a Scrollable, is a listenable similar to AnimationController.
Which means you could combine an AnimatedBuilder with a ScrollController, it would have the lovely effect to rebuild your widget automatically on a scroll. Perfect for this situation, right?
Combining everything into an example:
In the following example, you'll see an overlay that follows a widget inside ListView and shares the same height.
import 'package:flutter/material.dart';
import 'package:flutter/scheduler.dart';
class MyHomePage extends StatefulWidget {
const MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
final controller = ScrollController();
OverlayEntry sticky;
GlobalKey stickyKey = GlobalKey();
#override
void initState() {
if (sticky != null) {
sticky.remove();
}
sticky = OverlayEntry(
builder: (context) => stickyBuilder(context),
);
SchedulerBinding.instance.addPostFrameCallback((_) {
Overlay.of(context).insert(sticky);
});
super.initState();
}
#override
void dispose() {
sticky.remove();
super.dispose();
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: ListView.builder(
controller: controller,
itemBuilder: (context, index) {
if (index == 6) {
return Container(
key: stickyKey,
height: 100.0,
color: Colors.green,
child: const Text("I'm fat"),
);
}
return ListTile(
title: Text(
'Hello $index',
style: const TextStyle(color: Colors.white),
),
);
},
),
);
}
Widget stickyBuilder(BuildContext context) {
return AnimatedBuilder(
animation: controller,
builder: (_,Widget child) {
final keyContext = stickyKey.currentContext;
if (keyContext != null) {
// widget is visible
final box = keyContext.findRenderObject() as RenderBox;
final pos = box.localToGlobal(Offset.zero);
return Positioned(
top: pos.dy + box.size.height,
left: 50.0,
right: 50.0,
height: box.size.height,
child: Material(
child: Container(
alignment: Alignment.center,
color: Colors.purple,
child: const Text("^ Nah I think you're okay"),
),
),
);
}
return Container();
},
);
}
}
Note:
When navigating to a different screen, call following otherwise sticky would stay visible.
sticky.remove();
This is (I think) the most straightforward way to do this.
Copy-paste the following into your project.
UPDATE: using RenderProxyBox results in a slightly more correct implementation, because it's called on every rebuild of the child and its descendants, which is not always the case for the top-level build() method.
NOTE: This is not exactly an efficient way to do this, as pointed by Hixie here. But it is the easiest.
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
typedef void OnWidgetSizeChange(Size size);
class MeasureSizeRenderObject extends RenderProxyBox {
Size? oldSize;
OnWidgetSizeChange onChange;
MeasureSizeRenderObject(this.onChange);
#override
void performLayout() {
super.performLayout();
Size newSize = child!.size;
if (oldSize == newSize) return;
oldSize = newSize;
WidgetsBinding.instance!.addPostFrameCallback((_) {
onChange(newSize);
});
}
}
class MeasureSize extends SingleChildRenderObjectWidget {
final OnWidgetSizeChange onChange;
const MeasureSize({
Key? key,
required this.onChange,
required Widget child,
}) : super(key: key, child: child);
#override
RenderObject createRenderObject(BuildContext context) {
return MeasureSizeRenderObject(onChange);
}
#override
void updateRenderObject(
BuildContext context, covariant MeasureSizeRenderObject renderObject) {
renderObject.onChange = onChange;
}
}
Then, simply wrap the widget whose size you would like to measure with MeasureSize.
var myChildSize = Size.zero;
Widget build(BuildContext context) {
return ...(
child: MeasureSize(
onChange: (size) {
setState(() {
myChildSize = size;
});
},
child: ...
),
);
}
So yes, the size of the parent cannot can depend on the size of the child if you try hard enough.
Personal anecdote - This is handy for restricting the size of widgets like Align, which likes to take up an absurd amount of space.
Here's a sample on how you can use LayoutBuilder to determine the widget's size.
Since LayoutBuilder widget is able to determine its parent widget's constraints, one of its use case is to be able to have its child widgets adapt to their parent's dimensions.
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
var dimension = 40.0;
increaseWidgetSize() {
setState(() {
dimension += 20;
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(children: <Widget>[
Text('Dimension: $dimension'),
Container(
color: Colors.teal,
alignment: Alignment.center,
height: dimension,
width: dimension,
// LayoutBuilder inherits its parent widget's dimension. In this case, the Container in teal
child: LayoutBuilder(builder: (context, constraints) {
debugPrint('Max height: ${constraints.maxHeight}, max width: ${constraints.maxWidth}');
return Container(); // create function here to adapt to the parent widget's constraints
}),
),
]),
),
floatingActionButton: FloatingActionButton(
onPressed: increaseWidgetSize,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}
Demo
Logs
I/flutter (26712): Max height: 40.0, max width: 40.0
I/flutter (26712): Max height: 60.0, max width: 60.0
I/flutter (26712): Max height: 80.0, max width: 80.0
I/flutter (26712): Max height: 100.0, max width: 100.0
Update: You can also use MediaQuery to achieve similar function.
#override
Widget build(BuildContext context) {
var screenSize = MediaQuery.of(context).size ;
if (screenSize.width > layoutSize){
return Widget();
} else {
return Widget(); /// Widget if doesn't match the size
}
}
Let me give you a widget for that
class SizeProviderWidget extends StatefulWidget {
final Widget child;
final Function(Size) onChildSize;
const SizeProviderWidget(
{Key? key, required this.onChildSize, required this.child})
: super(key: key);
#override
_SizeProviderWidgetState createState() => _SizeProviderWidgetState();
}
class _SizeProviderWidgetState extends State<SizeProviderWidget> {
#override
void initState() {
///add size listener for first build
_onResize();
super.initState();
}
void _onResize() {
WidgetsBinding.instance?.addPostFrameCallback((timeStamp) {
if (context.size is Size) {
widget.onChildSize(context.size!);
}
});
}
#override
Widget build(BuildContext context) {
///add size listener for every build uncomment the fallowing
///_onResize();
return widget.child;
}
}
EDIT
Just wrap the SizeProviderWidget with OrientationBuilder to make it respect the orientation of the device
I made this widget as a simple stateless solution:
class ChildSizeNotifier extends StatelessWidget {
final ValueNotifier<Size> notifier = ValueNotifier(const Size(0, 0));
final Widget Function(BuildContext context, Size size, Widget child) builder;
final Widget child;
ChildSizeNotifier({
Key key,
#required this.builder,
this.child,
}) : super(key: key) {}
#override
Widget build(BuildContext context) {
WidgetsBinding.instance.addPostFrameCallback(
(_) {
notifier.value = (context.findRenderObject() as RenderBox).size;
},
);
return ValueListenableBuilder(
valueListenable: notifier,
builder: builder,
child: child,
);
}
}
Use it like this
ChildSizeNotifier(
builder: (context, size, child) {
// size is the size of the text
return Text(size.height > 50 ? 'big' : 'small');
},
)
If I understand correctly, you want to measure the dimension of some arbitrary widgets, and you can wrap those widgets with another widget. In that case, the method in the this answer should work for you.
Basically the solution is to bind a callback in the widget lifecycle, which will be called after the first frame is rendered, from there you can access context.size. The catch is that you have to wrap the widget you want to measure within a stateful widget. And, if you absolutely need the size within build() then you can only access it in the second render (it's only available after the first render).
findRenderObject() returns the RenderBox which is used to give the size of the drawn widget and it should be called after the widget tree is built, so it must be used with some callback mechanism or addPostFrameCallback() callbacks.
class SizeWidget extends StatefulWidget {
#override
_SizeWidgetState createState() => _SizeWidgetState();
}
class _SizeWidgetState extends State<SizeWidget> {
final GlobalKey _textKey = GlobalKey();
Size textSize;
#override
void initState() {
super.initState();
WidgetsBinding.instance.addPostFrameCallback((_) => getSizeAndPosition());
}
getSizeAndPosition() {
RenderBox _cardBox = _textKey.currentContext.findRenderObject();
textSize = _cardBox.size;
setState(() {});
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Size Position"),
),
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Text(
"Currern Size of Text",
key: _textKey,
textAlign: TextAlign.center,
style: TextStyle(fontSize: 22, fontWeight: FontWeight.bold),
),
SizedBox(
height: 20,
),
Text(
"Size - $textSize",
textAlign: TextAlign.center,
),
],
),
);
}
}
Output:
There is no direct way to calculate the size of the widget, so to find that we have to take the help of the context of the widget.
Calling context.size returns us the Size object, which contains the height and width of the widget. context.size calculates the render box of a widget and returns the size.
Checkout https://medium.com/flutterworld/flutter-how-to-get-the-height-of-the-widget-be4892abb1a2
In cases where you don't want to wait for a frame to get the size, but want to know it before including it in your tree:
The simplest way is to follow the example of the BuildOwner documentation.
With the following you can just do
final size = MeasureUtil.measureWidget(MyWidgetTree());
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
/// Small utility to measure a widget before actually putting it on screen.
///
/// This can be helpful e.g. for positioning context menus based on the size they will take up.
///
/// NOTE: Use sparingly, since this takes a complete layout and sizing pass for the subtree you
/// want to measure.
///
/// Compare https://api.flutter.dev/flutter/widgets/BuildOwner-class.html
class MeasureUtil {
static Size measureWidget(Widget widget, [BoxConstraints constraints = const BoxConstraints()]) {
final PipelineOwner pipelineOwner = PipelineOwner();
final _MeasurementView rootView = pipelineOwner.rootNode = _MeasurementView(constraints);
final BuildOwner buildOwner = BuildOwner(focusManager: FocusManager());
final RenderObjectToWidgetElement<RenderBox> element = RenderObjectToWidgetAdapter<RenderBox>(
container: rootView,
debugShortDescription: '[root]',
child: widget,
).attachToRenderTree(buildOwner);
try {
rootView.scheduleInitialLayout();
pipelineOwner.flushLayout();
return rootView.size;
} finally {
// Clean up.
element.update(RenderObjectToWidgetAdapter<RenderBox>(container: rootView));
buildOwner.finalizeTree();
}
}
}
class _MeasurementView extends RenderBox with RenderObjectWithChildMixin<RenderBox> {
final BoxConstraints boxConstraints;
_MeasurementView(this.boxConstraints);
#override
void performLayout() {
assert(child != null);
child!.layout(boxConstraints, parentUsesSize: true);
size = child!.size;
}
#override
void debugAssertDoesMeetConstraints() => true;
}
This creates an entirely new render tree separate from the main one, and wont be shown on your screen.
So for example
print(
MeasureUtil.measureWidget(
Directionality(
textDirection: TextDirection.ltr,
child: Row(
mainAxisSize: MainAxisSize.min,
children: const [
Icon(Icons.abc),
SizedBox(
width: 100,
),
Text("Moin Meister")
],
),
),
),
);
Would give you Size(210.0, 24.0)
Might be this could help
Tested on Flutter: 2.2.3
Copy Below code this in your project.
import 'package:flutter/material.dart';
import 'package:flutter/scheduler.dart';
class WidgetSize extends StatefulWidget {
final Widget child;
final Function onChange;
const WidgetSize({
Key? key,
required this.onChange,
required this.child,
}) : super(key: key);
#override
_WidgetSizeState createState() => _WidgetSizeState();
}
class _WidgetSizeState extends State<WidgetSize> {
#override
Widget build(BuildContext context) {
SchedulerBinding.instance!.addPostFrameCallback(postFrameCallback);
return Container(
key: widgetKey,
child: widget.child,
);
}
var widgetKey = GlobalKey();
var oldSize;
void postFrameCallback(_) {
var context = widgetKey.currentContext;
if (context == null) return;
var newSize = context.size;
if (oldSize == newSize) return;
oldSize = newSize;
widget.onChange(newSize);
}
}
declare a variable to store Size
Size mySize = Size.zero;
Add following code to get the size:
child: WidgetSize(
onChange: (Size mapSize) {
setState(() {
mySize = mapSize;
print("mySize:" + mySize.toString());
});
},
child: ()
This is Remi's answer with null safety, since the edit queue is full, I have to post it here.
class MyHomePage extends StatefulWidget {
const MyHomePage({Key? key}) : super(key: key);
#override
MyHomePageState createState() => MyHomePageState();
}
class MyHomePageState extends State<MyHomePage> {
final controller = ScrollController();
OverlayEntry? sticky;
GlobalKey stickyKey = GlobalKey();
#override
void initState() {
sticky?.remove();
sticky = OverlayEntry(
builder: (context) => stickyBuilder(context),
);
SchedulerBinding.instance
.addPostFrameCallback((_) => Overlay.of(context)?.insert(sticky!));
super.initState();
}
#override
void dispose() {
sticky?.remove();
super.dispose();
}
#override
Widget build(BuildContext context) => Scaffold(
body: ListView.builder(
controller: controller,
itemBuilder: (context, index) {
if (index == 6) {
return Container(
key: stickyKey,
height: 100.0,
color: Colors.green,
child: const Text("I'm fat"),
);
}
return ListTile(
title: Text(
'Hello $index',
style: const TextStyle(color: Colors.white),
),
);
},
),
);
Widget stickyBuilder(BuildContext context) => AnimatedBuilder(
animation: controller,
builder: (_, Widget? child) {
final keyContext = stickyKey.currentContext;
if (keyContext != null) {
final box = keyContext.findRenderObject() as RenderBox;
final pos = box.localToGlobal(Offset.zero);
return Positioned(
top: pos.dy + box.size.height,
left: 50.0,
right: 50.0,
height: box.size.height,
child: Material(
child: Container(
alignment: Alignment.center,
color: Colors.purple,
child: const Text("Nah I think you're okay"),
),
),
);
}
return Container();
},
);
}
use the package: z_tools.
The steps:
1. change main file
void main() async {
runZoned(
() => runApp(
CalculateWidgetAppContainer(
child: Center(
child: LocalizedApp(delegate, MyApp()),
),
),
),
onError: (Object obj, StackTrace stack) {
print('global exception: obj = $obj;\nstack = $stack');
},
);
}
2. use in function
_Cell(
title: 'cal: Column-min',
callback: () async {
Widget widget1 = Column(
mainAxisSize: MainAxisSize.min,
children: [
Container(
width: 100,
height: 30,
color: Colors.blue,
),
Container(
height: 20.0,
width: 30,
),
Text('111'),
],
);
// size = Size(100.0, 66.0)
print('size = ${await getWidgetSize(widget1)}');
},
),
The easiest way is to use MeasuredSize it's a widget that calculates the size of it's child in runtime.
You can use it like so:
MeasuredSize(
onChange: (Size size) {
setState(() {
print(size);
});
},
child: Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
);
You can find it here: https://pub.dev/packages/measured_size
It's easy and still can be done in StatelessWidget.
class ColumnHeightWidget extends StatelessWidget {
#override
Widget build(BuildContext context) {
final scrollController = ScrollController();
final columnKey = GlobalKey();
_scrollToCurrentProgress(columnKey, scrollController);
return Scaffold(
body: SingleChildScrollView(
controller: scrollController,
child: Column(
children: [],
),
),
);
}
void _scrollToCurrentProgress(GlobalKey<State<StatefulWidget>> columnKey,
ScrollController scrollController) {
WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
final RenderBox renderBoxRed =
columnKey.currentContext.findRenderObject();
final height = renderBoxRed.size.height;
scrollController.animateTo(percentOfHeightYouWantToScroll * height,
duration: Duration(seconds: 1), curve: Curves.decelerate);
});
}
}
in the same manner you can calculate any widget child height and scroll to that position.
**Credit to #Manuputty**
class OrigChildWH extends StatelessWidget {
final Widget Function(BuildContext context, Size size, Widget? child) builder;
final Widget? child;
const XRChildWH({
Key? key,
required this.builder,
this.child,
}) : super(key: key);
#override
Widget build(BuildContext context) {
return OrientationBuilder(builder: (context, orientation) {
return ChildSizeNotifier(builder: builder);
});
}
}
class ChildSizeNotifier extends StatelessWidget {
final ValueNotifier<Size> notifier = ValueNotifier(const Size(0, 0));
final Widget Function(BuildContext context, Size size, Widget? child) builder;
final Widget? child;
ChildSizeNotifier({
Key? key,
required this.builder,
this.child,
}) : super(key: key);
#override
Widget build(BuildContext context) {
WidgetsBinding.instance!.addPostFrameCallback(
(_) {
notifier.value = (context.findRenderObject() as RenderBox).size;
},
);
return ValueListenableBuilder(
valueListenable: notifier,
builder: builder,
child: child,
);
}
}
**Simple to use:**
OrigChildWH(
builder: (context, size, child) {
//Your child here: mine:: Container()
return Container()
})