I am trying to implement the scrolling effect on the home screen on whatsap on iphone, where the search bar disappears first while scrolling the the rest of the scrolling takes place. Any idea on how to implement it ?
You can try using the SliverAppBar with a CustomScrollView.
return Scaffold(
//1
body: CustomScrollView(
slivers: <Widget>[
//2
SliverAppBar(
expandedHeight: 250.0,
flexibleSpace: FlexibleSpaceBar(
title: Text('Goa', textScaleFactor: 1),
background: Image.asset(
'assets/images/beach.png',
fit: BoxFit.fill,
),
),
),
//3
SliverList(
delegate: SliverChildBuilderDelegate(
(_, int index) {
return ListTile(
leading: Container(
padding: EdgeInsets.all(8),
width: 100,
child: Placeholder()),
title: Text('Place ${index + 1}', textScaleFactor: 2),
);
},
childCount: 20,
),
),
],
),
);
Related
I'm creating an app where I need to implement WhatsApp like AppBar i.e to hide app bar on scroll down and show on reverse.
You can use the SliverAppBar and CustomScrollView to achieve this effect. A sample implementation:
Widget build(BuildContext context) {
return Scaffold(
body: CustomScrollView(
slivers: <Widget>[
SliverAppBar(
pinned: false,
snap: false,
floating: false,
expandedHeight: 160.0,
flexibleSpace: const FlexibleSpaceBar(
title: Text('AppBar'),
),
),
SliverList(
delegate: SliverChildBuilderDelegate(
(BuildContext context, int index) {
return Container(
color: index.isOdd ? Colors.white : Colors.black12,
height: 100.0,
child: Center(
child: Text('$index', textScaleFactor: 5),
),
);
},
childCount: 50,
),
),
],
),
);
}
I'm trying to improve my app and want to wrap an existing FutureBuilder with a SliverList. Unfortunately I'm having a strange and incomprehensible scrolling behaviour.
Here's my code so far:
#override
Widget build(BuildContext context) {
return Container(
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Expanded(
child: CustomScrollView(
slivers: [
SliverAppBar(
expandedHeight: 300,
floating: true,
flexibleSpace: FlexibleSpaceBar(
title: Padding(
padding: EdgeInsets.fromLTRB(30, 10, 30, 10),
child: Text(
'some subtext here...',
style: TextStyle(
fontStyle: FontStyle.italic,
color: Colors.white,
fontSize: 12.0)),
),
background: Stack(
fit: StackFit.expand,
children: [
Container(
child: Image.network(
'https://dummyimage.com/600x400/000/fff',
fit: BoxFit.cover,
),
),
const DecoratedBox(
decoration: BoxDecoration(
gradient: LinearGradient(
begin: Alignment(0.0, 0.5),
end: Alignment(0.0, 0.0),
colors: <Color>[
Color(0xcc000000),
Color(0x55000000),
],
),
),
),
],
),
),
),
SliverPadding(
padding: EdgeInsets.only(top: 10),
sliver: SliverList(
delegate: SliverChildListDelegate([
Container(
child: FutureBuilder(
future: fetchData(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.data == null) {
return Text('loading...');
} else {
return ListView.builder(
scrollDirection: Axis.vertical,
shrinkWrap: true,
itemCount: snapshot.data.length,
itemBuilder: (BuildContext content, int index) {
// return Text('Text ' + snapshot.data[index].name);
return snapshot.hasData ? Card(
elevation: 4,
child: ListTile(
leading: CircleAvatar(
backgroundImage:
NetworkImage(snapshot.data[index].image_url),
),
trailing: Text('Test'),
title: Text(snapshot.data[index].name),
subtitle: Text(snapshot.data[index].latin_name, style: TextStyle(
fontStyle: FontStyle.italic,
)),
onTap: () {
/*Navigator.push(context,
new MaterialPageRoute(builder: (context)=> DetailPage(snapshot.data[index]))
);*/
print('tapped');
},
),
) : Text('no Data');
},
);
//return Text('loading complete');
}
}
),
),
],),
),
)
],
)),
],
));
}
The SliverAppBar gets displayed correctly, but unfortunately since adding the Slivers my FutureBuilder doesn't display anything at all.
After adding scrollDirection and shrinkWrap to the ListView the data get's displayed but I'm unable to scroll correctly.
When dragging it at the red area the List snaps back up right after releasing The SliverAppBar doesn't shrink either. When scrolling in the green area the Sliver Header works correctly and the Scrolling doesn't snap right at the top when releasing.
Has anyone had this issue before? Or could someone explain on why this could happen?
I have this design:
CustomScrollView(
controller: _scrollController,
slivers: <Widget>[
const SliverAppBar(
pinned: true,
expandedHeight: 250.0,
flexibleSpace: FlexibleSpaceBar(
title: Text('Demo'),
),
),
SliverList(
delegate: SliverChildListDelegate(
[
Text("sds"),
],
),
),
SliverGrid(
gridDelegate: SliverGridDelegateWithMaxCrossAxisExtent(
maxCrossAxisExtent: 200.0,
mainAxisSpacing: 10.0,
crossAxisSpacing: 10.0,
childAspectRatio: 4.0,
),
delegate: SliverChildBuilderDelegate(
(BuildContext context, int index) {
return Container(
alignment: Alignment.center,
color: Colors.teal[100 * (index % 9)],
child: Text('Grid Item $index'),
);
},
childCount: 10,
),
),
SliverFillRemaining(
child: ReorderableListView(
scrollController: _scrollController,
children: <Widget>[
for (final items in item)
Card(
color: Colors.blueGrey,
key: ValueKey(items),
elevation: 2,
child: ListTile(
title: Text(items),
leading: Icon(
Icons.work,
color: Colors.black,
),
),
),
],
onReorder: reorderData,
),
),
],
),
Everything between the SliverAppBar and the ReorderableListView is just an example of how it should work.
I need to order some elements so for that I use a ReorderableListView but this needs to be inside a CustomScrollView and using its scroll. Right now everything works except for the scroll. The SliverAppBar minimises when scrolling over the grid, but the ReorderableListView has it owns scroll.
Is there any way to cancel the second scroll and having these 2 elements working together?
I also uses this library https://pub.dev/packages/reorderables but if you have a look to the repo it seems abandoned (and I faced different issues)
I am trying to set up a SliverAppBar in a CustomScrollView using Flutter, and can't get to vertically center the title.
I already tried this solution (and this SO question is exactly what I want to do) but fortunately, it didn't work for me.
Here is my build method:
#override
Widget build(BuildContext context) {
return Scaffold(
body: CustomScrollView(
slivers: <Widget>[
SliverAppBar(
pinned: true,
expandedHeight: 200,
//backgroundColor: Colors.transparent,
flexibleSpace: FlexibleSpaceBar(
titlePadding: EdgeInsets.zero,
centerTitle: true,
title: Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
mainAxisAlignment: MainAxisAlignment.center,
mainAxisSize: MainAxisSize.min,
children: <Widget>[
Text("Should be centered", textAlign: TextAlign.center),
],
),
background: Image.asset("assets/earth.jpg", fit: BoxFit.cover),
),
actions: <Widget>[
IconButton(
icon: const Icon(Icons.menu),
tooltip: "Menu",
onPressed: () {
// onPressed handler
},
),
],
),
SliverFixedExtentList(
itemExtent: 50,
delegate: SliverChildBuilderDelegate(
(BuildContext context, int index) {
return Container(
alignment: Alignment.center,
color: Colors.green,
child: Text("Index n°$index"),
);
},
),
)
],
),
);
}
I really don't understand what is wrong and why it isn't centered. I observed that the column is way too big when setting mainAxisSize to mainAxisSize.max.
Any idea?
Thanks in advance!
I tinkered around a bit in your code and was able to center it. So the main problem here was the expandedHeight. This height expands the SliverAppBar both upwards and downwards meaning that half of that 200 was always above the screen. Taking that into consideration, you would be trying to center the text in only the bottom half of the app bar. The simplest way was to just use Flexible to size the items relative to their container. Here's the working code:
#override
Widget build(BuildContext context) {
return Scaffold(
body: CustomScrollView(
slivers: <Widget>[
SliverAppBar(
pinned: true,
expandedHeight: 200,
//backgroundColor: Colors.transparent,
flexibleSpace: FlexibleSpaceBar(
titlePadding: EdgeInsets.zero,
centerTitle: true,
title: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Flexible(
flex: 3,
child: Container(),
),
Flexible(
flex: 1,
child:
Text("Should be centered", textAlign: TextAlign.center),
),
Flexible(
flex: 1,
child: Container(),
),
],
),
background: Image.asset("assets/earth.png", fit: BoxFit.cover),
),
actions: <Widget>[
IconButton(
icon: const Icon(Icons.menu),
tooltip: "Menu",
onPressed: () {
// onPressed handler
},
),
],
),
SliverFixedExtentList(
itemExtent: 50,
delegate: SliverChildBuilderDelegate(
(BuildContext context, int index) {
return Container(
alignment: Alignment.center,
color: Colors.green,
child: Text("Index n°$index"),
);
},
),
)
],
),
);
}
A way without empty containers
#override
Widget build(BuildContext context) {
return Scaffold(
body: CustomScrollView(
slivers: <Widget>[
SliverAppBar(
pinned: true,
expandedHeight: 200,
flexibleSpace: FlexibleSpaceBar(
titlePadding: EdgeInsets.zero,
centerTitle: true,
title: SizedBox(
height: 130,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text("Should be centered", textAlign: TextAlign.center),
],
),
),
background: Image.asset("assets/earth.png", fit: BoxFit.cover),
),
actions: <Widget>[
IconButton(
icon: const Icon(Icons.menu),
tooltip: "Menu",
onPressed: () {
// onPressed handler
},
),
],
),
SliverFixedExtentList(
itemExtent: 50,
delegate: SliverChildBuilderDelegate(
(BuildContext context, int index) {
return Container(
alignment: Alignment.center,
color: Colors.green,
child: Text("Index n°$index"),
);
},
),
)
],
),
);
}
Instead of using a FlexibleSpaceBar use a different Widget.
flexibleSpace: Padding(
padding: EdgeInsets.all(4),
child: Container(),
}),
),
Kinda like what Pedro said earlier, you can instead use the flexibleSpace parameter in SliverAppBar, and then center things from there. This is what I did.
SliverAppBar(
flexibleSpace: Center(
child: Text("27 is my favorite number")
)
)
Has anyone used Gradient in SliverAppBar? I can do it in FlexibleSpace when it's expanded, but when it's collapsed it gets a solid color. Is it possible to treat this?
Wrap a new Container Widget in FlexibleSpaceBar, then add BoxDecoration, LinearGradient under the container.
Unless I'm missing something, this should do what you're asking.
Before it's scrolled it looks like this:
And after scrolling like this:
import 'package:flutter/material.dart';
void main() => runApp(GradientAppBar());
class GradientAppBar extends StatefulWidget {
#override
_GradientAppBarState createState() => _GradientAppBarState();
}
class _GradientAppBarState extends State<GradientAppBar> {
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
body: CustomScrollView(
slivers: <Widget>[
SliverAppBar(
pinned: true,
expandedHeight: 100,
flexibleSpace: Container(
decoration: BoxDecoration(
gradient: LinearGradient(
colors: [
Colors.black,
Colors.white,
],
),
),
),
title: Text("This app bar has a gradient!"),
),
SliverList(
delegate: SliverChildListDelegate(
[
Container(
color: Colors.blue,
height: 500,
),
Divider(),
Container(
color: Colors.black12,
height: 500,
),
Divider(),
Container(
color: Colors.lightBlue,
height: 500,
),
Divider(),
Container(
color: Colors.lightGreen,
height: 500,
),
Divider(),
],
),
),
],
),
),
);
}
}
show this from Flutter documention:
CustomScrollView(
slivers: <Widget>[
const SliverAppBar(
pinned: true,
expandedHeight: 250.0,
flexibleSpace: FlexibleSpaceBar(
title: Text('Demo'),
),
),
SliverGrid(
gridDelegate: SliverGridDelegateWithMaxCrossAxisExtent(
maxCrossAxisExtent: 200.0,
mainAxisSpacing: 10.0,
crossAxisSpacing: 10.0,
childAspectRatio: 4.0,
),
delegate: SliverChildBuilderDelegate(
(BuildContext context, int index) {
return Container(
alignment: Alignment.center,
color: Colors.teal[100 * (index % 9)],
child: Text('grid item $index'),
);
},
childCount: 20,
),
),
SliverFixedExtentList(
itemExtent: 50.0,
delegate: SliverChildBuilderDelegate(
(BuildContext context, int index) {
return Container(
alignment: Alignment.center,
color: Colors.lightBlue[100 * (index % 9)],
child: Text('list item $index'),
);
},
),
),
],
)