If you look at the [Source Code] of SystemChannels (https://github.com/flutter/flutter/blob/master/packages/flutter/lib/src/services/system_channels.dart), the contents use MethodChannel, EventChannel, etc. You can see that. Please refer to here for Method Channel and Event Channel.

Types of System Channels

Several types are available for each application. The list is shown below.

Sample code

lifecycle

Life cycle listener

SystemChannels.lifecycle.setMessageHandler((message){
  print('<SystemChannels.lifecycle> $message');
  /*
  AppLifecycleState.paused
  AppLifecycleState.inactive
  AppLifecycleState.resumed
  AppLifecycleState.suspending
  AppLifecycleState.detached
   */
  return Future<String>.value();
});

navigation

Navigation operation listener

SystemChannels.navigation.setMethodCallHandler((call) {
  print('<SystemChannels.navigation> ${call.method} (${call.arguments})');
  /*
   popRoute
   pushRoute
   */
  return Future<dynamic>.value();
});

system It can't be used for anything, it's not used, and you can ignore it.

For the time being, set only the callback

SystemChannels.system.setMessageHandler((message) {
  print('<SystemChannels.system> $message');
  return Future<dynamic>.value();
});

accessibility

Text-to-speech sample

SemanticsService.announce('Hello world', TextDirection.ltr)

The Flutter Framework internal implementation of is below.

Reference

Dart

final AnnounceSemanticsEvent event = AnnounceSemanticsEvent('Hello world', TextDirection.ltr);
SystemChannels.accessibility.send(event.toMap());

platform

Exit the app

SystemNavigator.pop()

The Flutter Framework internal implementation of is below.

Exit the app

SystemChannels.platform.invokeMethod('SystemNavigator.pop');

platform_views

It is used in flutter_web, so please refer to it.

Create a view like this

final Map<String, dynamic> args = <String, dynamic>{
  'id': 1,
  'viewType': 'Create WebView',
};
SystemChannels.platform_views.invokeMethod('create', args);

skia

Skia cache size setting. There is no other function, and now I can only do this ...

const maxBytes = 4 * 1024 * 1024;
SystemChannels.skia.invokeMethod('setResourceCacheMaxBytes', maxBytes);

keyEvent

Key input listener

SystemChannels.keyEvent.setMessageHandler((message) {
  print('<SystemChannels.keyEvent> $message');
  return Future<dynamic>.value();
});

textInput

Keyboard display ON/OFF

SystemChannels.textInput.invokeMethod('TextInput.show');
SystemChannels.textInput.invokeMethod('TextInput.hide');