Route Transition Animations in Flutter: Customizing Navigation with PageRouteBuilder

5.4.3 Route Transition Animations

In the world of mobile app development, user experience is paramount. One of the key aspects that contribute to a seamless user experience is the transition animations between different screens or routes. Flutter, with its rich set of widgets and tools, provides developers with the ability to customize these animations to enhance the overall feel of the app. In this section, we will delve into the intricacies of route transition animations in Flutter, focusing on how to implement and customize them using PageRouteBuilder.

Custom Route Transitions

Flutter’s navigation system is built around the concept of routes. By default, Flutter provides basic transition animations such as slide transitions when navigating between routes. However, to create a unique and engaging user experience, you might want to customize these transitions. Custom route transitions allow you to define how a new screen appears and how the current screen disappears, providing a more cohesive and branded experience.

Using PageRouteBuilder

The PageRouteBuilder class in Flutter is a powerful tool that allows developers to define custom transitions. It provides two main parameters: pageBuilder and transitionsBuilder.

Implementation

Let’s start with a basic example of using PageRouteBuilder to create a fade transition when navigating to a new page.

Navigator.push(
  context,
  PageRouteBuilder(
    pageBuilder: (context, animation, secondaryAnimation) => NewPage(),
    transitionsBuilder: (context, animation, secondaryAnimation, child) {
      return FadeTransition(
        opacity: animation,
        child: child,
      );
    },
  ),
);

Breaking Down the Parameters

• pageBuilder: This parameter is responsible for building the new page that you want to navigate to. It takes three arguments: context, animation, and secondaryAnimation. The animation and secondaryAnimation are used to define the transition animations.

• transitionsBuilder: This parameter defines how the transition animation should be performed. It also takes four arguments: context, animation, secondaryAnimation, and child. The child is the widget returned by the pageBuilder. In the example above, we use a FadeTransition to gradually change the opacity of the new page from 0 to 1.

Custom Animations

While the FadeTransition is a simple and elegant way to transition between routes, Flutter offers a variety of other transition widgets that you can use to create more dynamic effects.

SlideTransition

A SlideTransition can be used to slide a new page in from a specific direction. Here’s how you can implement a slide transition from the bottom:

Navigator.push(
  context,
  PageRouteBuilder(
    pageBuilder: (context, animation, secondaryAnimation) => NewPage(),
    transitionsBuilder: (context, animation, secondaryAnimation, child) {
      const begin = Offset(0.0, 1.0);
      const end = Offset.zero;
      const curve = Curves.ease;

      var tween = Tween(begin: begin, end: end).chain(CurveTween(curve: curve));

      var offsetAnimation = animation.drive(tween);

      return SlideTransition(
        position: offsetAnimation,
        child: child,
      );
    },
  ),
);

ScaleTransition

A ScaleTransition can be used to scale the new page in, creating a zoom effect:

Navigator.push(
  context,
  PageRouteBuilder(
    pageBuilder: (context, animation, secondaryAnimation) => NewPage(),
    transitionsBuilder: (context, animation, secondaryAnimation, child) {
      var tween = Tween(begin: 0.0, end: 1.0).chain(CurveTween(curve: Curves.ease));

      return ScaleTransition(
        scale: animation.drive(tween),
        child: child,
      );
    },
  ),
);

Combining Animations

For more complex effects, you can combine multiple animations. For instance, you can create a transition that both slides and fades a new page in:

Navigator.push(
  context,
  PageRouteBuilder(
    pageBuilder: (context, animation, secondaryAnimation) => NewPage(),
    transitionsBuilder: (context, animation, secondaryAnimation, child) {
      const begin = Offset(0.0, 1.0);
      const end = Offset.zero;
      const curve = Curves.ease;

      var tween = Tween(begin: begin, end: end).chain(CurveTween(curve: curve));
      var offsetAnimation = animation.drive(tween);

      return SlideTransition(
        position: offsetAnimation,
        child: FadeTransition(
          opacity: animation,
          child: child,
        ),
      );
    },
  ),
);

Shared Axis Transition (Advanced)

For developers looking to implement more advanced transitions, the animations package provides a set of pre-defined Material motion transitions. One such transition is the Shared Axis Transition, which animates changes in the position of elements along a shared axis.

To use the Shared Axis Transition, you need to add the animations package to your pubspec.yaml:

dependencies:
  flutter:
    sdk: flutter
  animations: ^2.0.0

Here’s an example of implementing a Shared Axis Transition:

import 'package:animations/animations.dart';

Navigator.push(
  context,
  PageRouteBuilder(
    pageBuilder: (context, animation, secondaryAnimation) => NewPage(),
    transitionsBuilder: (context, animation, secondaryAnimation, child) {
      return SharedAxisTransition(
        animation: animation,
        secondaryAnimation: secondaryAnimation,
        transitionType: SharedAxisTransitionType.horizontal,
        child: child,
      );
    },
  ),
);

Best Practices

When implementing custom route transitions, it’s essential to keep a few best practices in mind:

• Smooth Transitions: Ensure that transitions are smooth and do not cause jarring effects. This can be achieved by using appropriate curves and durations.

• Consistency: Maintain consistency in transition styles throughout your app to provide a cohesive user experience.

• Performance: Avoid overly complex animations that could impact performance, especially on lower-end devices.

• User Control: Allow users to control transitions, such as providing a way to skip or speed up animations if needed.

Practice Exercises

To reinforce your understanding of route transition animations, try implementing the following exercises:

Exercise 1: Slide-Up Transition for Modals

Implement a slide-up transition for a modal dialog using PageRouteBuilder.

Exercise 2: Custom Transition with Scale and Fade

Create a custom transition that scales and fades in the new route simultaneously.

Conclusion

Customizing route transition animations in Flutter can significantly enhance the user experience of your app. By leveraging PageRouteBuilder and the animations package, you can create smooth, consistent, and visually appealing transitions that align with your app’s design and branding. Remember to keep transitions subtle and performance-friendly to ensure a seamless experience for your users.

Quiz Time!