# Page transitions replaced by ZoomPageTransitionsBuilder

> Using the latest page transition instead of the old one.




:::important
These breaking change docs are accurate, as of the release
under which they are published. Over time, the
workarounds described here might become inaccurate.
We don't, in general, keep these breaking change docs up
to date as of each release.

The [breaking change index file](/release/breaking-changes)
lists the docs created for each release.
:::


## Summary

In order to ensure that libraries follow the latest OEM behavior,
the default page transition builders now use
`ZoomPageTransitionsBuilder` on all platforms (excluding iOS and macOS)
instead of `FadeUpwardsPageTransitionsBuilder`.

## Context

The `FadeUpwardsPageTransitionsBuilder` (provided with the first
Flutter release), defined a page transition that's
similar to the one provided by Android O. This page transitions builder
will eventually be deprecated on Android, as per Flutter's
[deprecation policy](/release/compatibility-policy#deprecation-policy).

`ZoomPageTransitionsBuilder`, the new page transition builder for
Android, Linux, and Windows, defines a page transition that's similar to
the one provided by Android Q and R.

According to the [Style guide for Flutter repo][],
the framework will follow the latest OEM behavior.
Page transition builders using `FadeUpwardsPageTransitionsBuilder`
are all switched to the `ZoomPageTransitionsBuilder`.
When the current `TargetPlatform` doesn't have
`PageTransitionsBuilder` defined in the `ThemeData.pageTransitionsTheme`,
`ZoomPageTransitionsBuilder` is used as the default.

[Style guide for Flutter repo]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md
## Description of change

`PageTransitionsBuilder`s defined in
`PageTransitionsTheme._defaultBuilders` have changed from
`FadeUpwardsPageTransitionsBuilder` to
`ZoomPageTransitionsBuilder` for `TargetPlatform.android`,
`TargetPlatform.linux` and `TargetPlatform.windows`.

## Migration guide

If you want to switch back to the previous page transition builder
(`FadeUpwardsPageTransitionsBuilder`), you should define builders
explicitly for the target platforms.

Code before migration:

```dart
MaterialApp(
  theme: ThemeData(colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple)),
)
```

Code after migration:

```dart
MaterialApp(
  theme: ThemeData(
    pageTransitionsTheme: const PageTransitionsTheme(
      builders: <TargetPlatform, PageTransitionsBuilder>{
        TargetPlatform.android: FadeUpwardsPageTransitionsBuilder(), // Apply this to every platforms you need.
      },
    ),
  ),
)
```

If you want to apply the same page transition builder to all platforms:

```dart
MaterialApp(
  theme: ThemeData(
    pageTransitionsTheme: PageTransitionsTheme(
      builders: Map<TargetPlatform, PageTransitionsBuilder>.fromIterable(
        TargetPlatform.values,
        value: (dynamic _) => const FadeUpwardsPageTransitionsBuilder(),
      ),
    ),
  ),
)

```

### Tests migration

If you used to try to find widgets but failed with *Too many elements*
using the new transition, and saw errors similar to the following:

```plaintext
══╡ EXCEPTION CAUGHT BY FLUTTER TEST FRAMEWORK ╞════════════════════════════════════════════════════
The following StateError was thrown running a test:
Bad state: Too many elements

When the exception was thrown, this was the stack:
#0      Iterable.single (dart:core/iterable.dart:656:24)
#1      WidgetController.widget (package:flutter_test/src/controller.dart:69:30)
#2      main.<anonymous closure> (file:///path/to/your/test.dart:1:2)
```

You should migrate your tests by using the
`descendant` scope for `Finder`s with the specific widget type.
Below is the example of `DataTable`'s test:

Test before migration:

```dart
final Finder finder = find.widgetWithIcon(Transform, Icons.arrow_upward);
```

Test after migration:

```dart
final Finder finder = find.descendant(
  of: find.byType(DataTable),
  matching: find.widgetWithIcon(Transform, Icons.arrow_upward),
);
```

Widgets that typically need to migrate the finder scope are:
`Transform`, `FadeTransition`, `ScaleTransition`, and `ColoredBox`.

## Timeline

Landed in version: 2.13.0-1.0.pre<br>
In stable release: 3.0.0

## References

API documentation:

* [`ZoomPageTransitionsBuilder`][]
* [`FadeUpwardsPageTransitionsBuilder`][]
* [`PageTransitionsTheme`][]

Relevant issues:

* [Issue 43277][]

Relevant PR:

* [PR 100812][]

[`ZoomPageTransitionsBuilder`]: https://api.flutter.dev/flutter/material/ZoomPageTransitionsBuilder-class.html
[`FadeUpwardsPageTransitionsBuilder`]: https://api.flutter.dev/flutter/material/FadeUpwardsPageTransitionsBuilder-class.html
[`PageTransitionsTheme`]: https://api.flutter.dev/flutter/material/PageTransitionsTheme-class.html
[Issue 43277]: https://github.com/flutter/flutter/issues/43277
[PR 100812]: https://github.com/flutter/flutter/pull/100812