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in android, you typically subclass view, or use a pre-existing view,
to override and implement methods that achieve the desired behavior.
in flutter, build a custom widget by composing
smaller widgets (instead of extending them).
it is somewhat similar to implementing a custom ViewGroup
in android, where all the building blocks are already existing,
but you provide a different behavior—for example,
custom layout logic.
for example, how do you build a CustomButton that takes a label in
the constructor? create a CustomButton that composes a ElevatedButton with
a label, rather than by extending ElevatedButton:
<code_start>
class CustomButton extends StatelessWidget {
final string label;
const CustomButton(this.label, {super.key});
@override
widget build(BuildContext context) {
return ElevatedButton(
onPressed: () {},
child: text(label),
);
}
}
<code_end>
then use CustomButton, just as you’d use any other flutter widget:
<code_start>
@override
widget build(BuildContext context) {
return const center(
child: CustomButton('Hello'),
);
}
<code_end>
<topic_end>
<topic_start>
intents
<topic_end>
<topic_start>
what is the equivalent of an intent in flutter?
in android, there are two main use cases for intents: navigating between
activities, and communicating with components. flutter, on the other hand,
does not have the concept of intents, although you can still start intents
through native integrations (using a plugin).
flutter doesn’t really have a direct equivalent to activities and fragments;
rather, in flutter you navigate between screens, using a navigator and
routes, all within the same activity.
a route is an abstraction for a “screen” or “page” of an app, and a
navigator is a widget that manages routes. a route roughly maps to an
activity, but it does not carry the same meaning. a navigator can push
and pop routes to move from screen to screen. navigators work like a stack
on which you can push() new routes you want to navigate to, and from
which you can pop() routes when you want to “go back”.
in android, you declare your activities inside the app’s AndroidManifest.xml.
in flutter, you have a couple options to navigate between pages:
the following example builds a map.
<code_start>
void main() {
runApp(MaterialApp(
home: const MyAppHome(), // becomes the route named '/'.
routes: <string, WidgetBuilder>{
'/a': (context) => const MyPage(title: 'page a'),
'/b': (context) => const MyPage(title: 'page b'),
'/c': (context) => const MyPage(title: 'page c'),
},
));
}
<code_end>
navigate to a route by pushing its name to the navigator.
<code_start>
Navigator.of(context).pushNamed('/b');
<code_end>
the other popular use-case for intents is to call external components such
as a camera or file picker. for this, you would need to create a native platform
integration (or use an existing plugin).
to learn how to build a native platform integration,
see developing packages and plugins.
<topic_end>
<topic_start>
how do i handle incoming intents from external applications in flutter?
flutter can handle incoming intents from android by directly talking to the
android layer and requesting the data that was shared.
the following example registers a text share intent filter on the native
activity that runs our flutter code, so other apps can share text with
our flutter app.
the basic flow implies that we first handle the shared text data on the
android native side (in our activity), and then wait until flutter requests
for the data to provide it using a MethodChannel.
first, register the intent filter for all intents in AndroidManifest.xml:
then in MainActivity, handle the intent, extract the text that was
shared from the intent, and hold onto it. when flutter is ready to process,
it requests the data using a platform channel, and it’s sent
across from the native side:
finally, request the data from the flutter side
when the widget is rendered:
<code_start>
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
void main() {
runApp(const SampleApp());
}