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A good place to find Flutter packages is pub.dev.<topic_end>
<topic_start>
Activities and fragments
<topic_end>
<topic_start>
What are the equivalent of activities and fragments in Flutter?
In Android, an Activity represents a single focused thing the user can do.
A Fragment represents a behavior or a portion of user interface.
Fragments are a way to modularize your code, compose sophisticated
user interfaces for larger screens, and help scale your application UI.
In Flutter, both of these concepts fall under the umbrella of Widgets.To learn more about the UI for building Activities and Fragments,
see the community-contributed Medium article,
Flutter for Android Developers: How to design Activity UI in Flutter.As mentioned in the Intents section,
screens in Flutter are represented by Widgets since everything is
a widget in Flutter. Use a Navigator to move between different
Routes that represent different screens or pages,
or perhaps different states or renderings of the same data.<topic_end>
<topic_start>
How do I listen to Android activity lifecycle events?
In Android, you can override methods from the Activity to capture lifecycle
methods for the activity itself, or register ActivityLifecycleCallbacks on
the Application. In Flutter, you have neither concept, but you can instead
listen to lifecycle events by hooking into the WidgetsBinding observer and
listening to the didChangeAppLifecycleState() change event.The observable lifecycle events are:For more details on the meaning of these states, see the
AppLifecycleStatus documentation.As you might have noticed, only a small minority of the Activity
lifecycle events are available; while FlutterActivity does
capture almost all the activity lifecycle events internally and
send them over to the Flutter engine, they’re mostly shielded
away from you. Flutter takes care of starting and stopping the
engine for you, and there is little reason for needing to
observe the activity lifecycle on the Flutter side in most cases.
If you need to observe the lifecycle to acquire or release any
native resources, you should likely be doing it from the native side,
at any rate.Here’s an example of how to observe the lifecycle status of the
containing activity:
<code_start>import 'package:flutter/widgets.dart';
class LifecycleWatcher extends StatefulWidget {
const LifecycleWatcher({super.key});
@override
State<LifecycleWatcher> createState() => _LifecycleWatcherState();
}
class _LifecycleWatcherState extends State<LifecycleWatcher>
with WidgetsBindingObserver {
AppLifecycleState? _lastLifecycleState;
@override
void initState() {
super.initState();
WidgetsBinding.instance.addObserver(this);
}
@override
void dispose() {
WidgetsBinding.instance.removeObserver(this);
super.dispose();
}
@override
void didChangeAppLifecycleState(AppLifecycleState state) {
setState(() {
_lastLifecycleState = state;
});
}
@override
Widget build(BuildContext context) {
if (_lastLifecycleState == null) {
return const Text(
'This widget has not observed any lifecycle changes.',
textDirection: TextDirection.ltr,
);
}
return Text(
'The most recent lifecycle state this widget observed was: $_lastLifecycleState.',
textDirection: TextDirection.ltr,
);
}
}
void main() {
runApp(const Center(child: LifecycleWatcher()));
}<code_end>
<topic_end>
<topic_start>
Layouts
<topic_end>
<topic_start>
What is the equivalent of a LinearLayout?
In Android, a LinearLayout is used to lay your widgets out
linearly—either horizontally or vertically.
In Flutter, use the Row or Column
widgets to achieve the same result.If you notice the two code samples are identical with the exception of the
“Row” and “Column” widget. The children are the same and this feature can be
exploited to develop rich layouts that can change overtime with the same
children.
<code_start>@override
Widget build(BuildContext context) {
return const Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text('Row One'),
Text('Row Two'),
Text('Row Three'),
Text('Row Four'),
],