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mouse users have more input options. they can use a wheel
or scrollbar to scroll, which generally eliminates the need
for dedicated drag handles. if you look at the macOS
finder or windows explorer, you’ll see that they work
this way: you just select an item and start dragging.
in flutter, you can implement drag and drop in many
ways. discussing specific implementations is outside
the scope of this article, but some high level options
are:
use the draggable and DragTarget APIs
directly for a custom look and feel.
hook into onPan gesture events,
and move an object yourself within a parent stack.
use one of the pre-made list packages on pub.dev.
<topic_end>
<topic_start>
educate yourself on basic usability principles
of course, this page doesn’t constitute an exhaustive list
of the things you might consider. the more operating systems,
form factors, and input devices you support,
the more difficult it becomes to spec out every permutation in design.
taking time to learn basic usability principles as a
developer empowers you to make better decisions,
reduces back-and-forth iterations with design during production,
and results in improved productivity with better outcomes.
here are some resources to get you started:
<topic_end>
<topic_start>
update the UI based on orientation
in some situations,
you want to update the display of an app when the user
rotates the screen from portrait mode to landscape mode. for example,
the app might show one item after the next in portrait mode,
yet put those same items side-by-side in landscape mode.
in flutter, you can build different layouts depending
on a given orientation.
in this example, build a list that displays two columns in
portrait mode and three columns in landscape mode using the
following steps:
<topic_end>
<topic_start>
1. build a GridView with two columns
first, create a list of items to work with.
rather than using a normal list,
create a list that displays items in a grid.
for now, create a grid with two columns.
<code_start>
return GridView.count(
// a list with 2 columns
crossAxisCount: 2,
// ...
);
<code_end>
to learn more about working with GridViews,
see the creating a grid list recipe.
<topic_end>
<topic_start>
2. use an OrientationBuilder to change the number of columns
to determine the app’s current orientation, use the
OrientationBuilder widget.
the OrientationBuilder calculates the current orientation by
comparing the width and height available to the parent widget,
and rebuilds when the size of the parent changes.
using the orientation, build a list that displays two columns in portrait
mode, or three columns in landscape mode.
<code_start>
body: OrientationBuilder(
builder: (context, orientation) {
return GridView.count(
// create a grid with 2 columns in portrait mode,
// or 3 columns in landscape mode.
crossAxisCount: orientation == orientation.portrait ? 2 : 3,
);
},
),
<code_end>
info note
if you’re interested in the orientation of the screen,
rather than the amount of space available to the parent,
use MediaQuery.of(context).orientation instead of an
OrientationBuilder widget.
<topic_end>
<topic_start>
interactive example
<code_start>
import 'package:flutter/material.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
widget build(BuildContext context) {
const appTitle = 'orientation demo';
return const MaterialApp(
title: appTitle,
home: OrientationList(
title: appTitle,
),
);