Contents

Navigator's page APIs breaking change

Contents

Summary

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The Navigator's page APIs are refactored so that they can integrate into Flutter's other pop mechanisms.

Context

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The onPopPage was added for cleaning up pages after a page is about to be popped. To veto pop, return false in the callback. This does not work well with other popping mechanisms in the framework, such as PopScope and iOS back gestures.

To integrate the other pop mechanisms together, the page APIs need to be refactored.

Description of change

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The onDidRemovePage property replaces the onPopPage property. You can no longer veto a pop in the onDidRemovePage property. Instead, you are only responsible for updating the [pages].

The veto mechanism moves to the Page.canPop and Page.onPopInvoked. These function similar to how one uses the PopScope widget.

Migration guide

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Code before migration

dart
import 'package:flutter/material.dart';
const MaterialPage<void> page1 = MaterialPage<void>(child: PlaceHolder());
const MaterialPage<void> page2 = MaterialPage<void>(child: PlaceHolder());
const MaterialPage<void> page3 = MaterialPage<void>(child: PlaceHolder());

void main() {
  final List<Page<void>> pages = <Page<void>>[page1, page2, page3];
  runApp(
    MaterialApp(
      home: Navigator(
        pages: pages,
        onPopPage: (Route<Object?> route, Object? result) {
          if (route.settings == page2) {
            return false;
          }
          if (route.didPop) {
            pages.remove(route.settings);
            pages = pages.toList();
            return true;
          }
          return false;
        }
          
      ),
    ),
  );
}

Code after migration

dart
import 'package:flutter/material.dart';
const MaterialPage<void> page1 = MaterialPage<void>(child: PlaceHolder());
const MaterialPage<void> page2 = MaterialPage<void>(canPop: false, child: PlaceHolder());
const MaterialPage<void> page3 = MaterialPage<void>(child: PlaceHolder());

void main() {
  final List<Page<void>> pages = <Page<void>>[page1, page2, page3];
  runApp(
    MaterialApp(
      home: Navigator(
        pages: pages,
        onDidRemovePage: (Page<Object?> page) {
          pages.remove(page);
          pages = pages.toList();
        }
          
      ),
    ),
  );
}

Timeline

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Landed in version: TBD
In stable release: TBD

References

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API documentation:

Relevant issue:

Relevant PR:

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