Introduction

Creating smooth and engaging animations is one of the most exciting aspects of building apps in Flutter. To assist you in selecting the best animation widget for your requirements, we will go over the main ideas and methods for implementing animations in Flutter in this post. Let us start by going over the fundamentals of animation and how Flutter uses quick updates to the widget tree to simulate movement. We will then explore the various animation styles that Flutter offers, such as tween-based, physics-based, and pre-canned animations, each of which offers a special method for producing dynamic and captivating user interfaces. 

Additionally, we will examine popular UI/UX design animation patterns and offer suggestions for successfully implementing them in Flutter. Lastly, we will go over how to pick the best Flutter animation widget for your type of animation, including whether it is code-based or drawing-based, and whether to use programs like Rive or Lottie for animations that are more graphically intensive. With the help of this thorough guide, you will be able to choose the most appropriate animation technique for your Flutter apps.

What is the Essence of Motion in Flutter: Animation Basics

In Flutter, ‘animation’ is essentially a series of frames that are shown quickly one after the other to provide the impression of movement. With frame rates of up to 120 frames per second on contemporary devices, Flutter depends on its ability to redraw widgets quickly enough to replicate continuous motion, much like movies do. Flutter animations make use of this idea by updating the widget tree with each frame. Widgets like AnimatedBuilder, which invokes setState() on each frame, effectively handle this resource-intensive method, enabling responsive, fluid animations without the need for specialist hardware.

1. The Role of Ticker: Controlling Frame Updates

In Flutter, a Ticker is an object that executes a callback function on each frame. Since Ticker is typically controlled by the SingleTickerProviderStateMixin, which facilitates synchronizing animations with the widget lifetime, developers typically avoid using it directly. This is a simple illustration of a ticker that prints a message on each frame:

var ticker = Ticker((elapsed) => print('hello'));
ticker.start();

Always dispose of the Ticker after use to avoid memory leaks. This is where SingleTickerProviderStateMixin comes in handy; it makes maintenance easier by automatically assigning the Ticker to the state of your widget.

2. AnimationController: Driving Animation Progress

The Flutter animation engine, the AnimationController, provides playback control, including play, pause, reverse, and stop. Developers can view an animation's progress in real time by utilizing AnimationController. For educational purposes, we show how to control animation via a direct setState() call instead of the more popular method of pairing AnimationController with a Curve or Tween:

class _MyWidgetState extends State<MyWidget> 
    with SingleTickerProviderStateMixin<MyWidget> {
  AnimationController _controller;
  
  @override
  void initState() {
    super.initState();
    _controller = AnimationController(vsync: this);
    _controller.addListener(() {
      setState(() {
        // Update logic here
      });
    });
  }
  
  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

3. Creating a Custom Animation with setState

This example determines the current animation value and calls setState() with each frame to animate text to imitate accelerating from zero to the speed of light.

class _MyWidgetState extends State<MyWidget> 
    with SingleTickerProviderStateMixin<MyWidget> {
  AnimationController _controller;
  int speed = 0;
  
  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      vsync: this,
      duration: const Duration(seconds: 1),
    )..addListener(() {
      setState(() {
        speed = (_controller.value * 299792458).round();
      });
    });
    _controller.forward();
  }
  
  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }
  
  @override
  Widget build(BuildContext context) {
    return Text('$speed m/s');
  }
}

This example illustrates Flutter's ability to update states constantly at high speed, emulating fluid animations, by calculating the speed based on the current animation progress.

4. TweenAnimationBuilder: A More Concise Solution

TweenAnimationBuilder offers comparable capability in fewer lines of code for a simpler method. You can reduce complexity and improve maintainability by defining a Tween and duration instead of requiring an AnimationController or Ticker:

class MyPragmaticWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return TweenAnimationBuilder(
      tween: IntTween(begin: 0, end: 299792458),
      duration: const Duration(seconds: 1),
      builder: (BuildContext context, int speed, Widget child) {
        return Text('$speed m/s');
      },
    );
  }
}

By using Ticker, AnimationController, and setState() on every frame, developers may create unique animations with Flutter's animation system. Although TweenAnimationBuilder makes development easier, by fully controlling the updates for each frame, developers can create more inventive and effective animations by being aware of these lower-level techniques.

Types of Animations

Animations in Flutter can be broadly divided into three categories: tween-based, physics-based, and pre-canned. Each of these categories offers unique approaches to bringing user interface elements to life. These animations are used by developers to produce dynamic and aesthetically pleasing user interfaces. An outline of several animation styles and standard practices for successfully utilizing each are given in this section.

1. Tween Animation

With a beginning and ending state, a timeline, and a curve to regulate the timing and transition speed, tween animations—short for "in-betweening"—are characterized. Flutter computes intermediate values for tween animations, guaranteeing a seamless transition from beginning to end. For simple movements like fading, resizing, or color changes, this technique works well. With just the beginning and ending values, a duration, and a curve needed, Flutter's TweenAnimationBuilder widget offers a simple method for producing such animations. This method eliminates the need for laborious computations and produces effects that are refined but basic.

2. Physics-Based Animation

When user interface elements require realistic dynamics, such as bouncing or springing, physics-based animations can be helpful since they replicate real-world movement. Depending on the desired effect, these animations can be tailored to react organically to forces. The AnimationController.animateWith and SpringSimulation APIs, developers can give animations physical characteristics like gravity and friction to make objects behave like they would in the actual world. These physics-based animations provide interactions with more nuance and make the movement seem logical and natural to users.

3. Pre-Canned Animations

Additionally, Flutter provides pre-made animations, especially via the animations package on pub.dev. This package offers a collection of frequently used animations, such as fade-throughs, shared axis transitions, container transformations, and fade transitions. For basic UI elements like dialogs or activity transitions, pre-canned animations make it easier to develop animations that follow Material Design requirements. Developers may ensure compatibility with Flutter's design language while saving time by utilizing pre-built choices.

Common Animation Patterns

In UI/UX design, specific animation patterns are commonly used to produce captivating user experiences. Flutter offers particular classes and widgets to easily apply these patterns.

1. Animated List or Grid

One common pattern for interactive content is to animate the addition or removal of items in a grid or list. The AnimatedList widget in Flutter provides a simple method for animating list item changes. For instance, AnimatedList animates the transition to graphically represent changes made to an item. For list-based content, such as task lists or shopping carts, where content updates must be both educational and aesthetically pleasing, this design is perfect.

2. Shared Element Transition

An animation pattern known as the "shared element transition" allows an element, like a picture, to "move" from one page to another while undergoing changes in size, shape, or location. This may be accomplished in Flutter by using the Hero widget, which enables smooth route (page) transitions. The Hero widget improves the operation and appearance of apps by enabling the creation of fluid navigation effects, in which items expand or change to reveal more material.

3. Staggered Animation

In order to provide a cascade effect, staggered animations divide a longer animation sequence into smaller portions, with each sub-animation being delayed. With the help of controllers and tweens, Flutter allows developers to create staggered animations, in which each segment of the animation overlaps or plays sequentially. By establishing a rhythm that directs the user's attention from one piece to the next, this technique is especially helpful for onboarding screens or list item reveals.

How to Choose Which Flutter Animation Widget is Right for You

Knowing the type of animation you want to use is crucial when selecting an animation widget for your Flutter application. In general, there are two primary categories of animations in Flutter: drawing-based and code-based. Code-based animations usually make use of the built-in Flutter widget primitives and focus on improving the look or transitions of pre-existing widgets, such as altering text styles or colors. However, drawing-based animations are perfect for more graphic-heavy animations, like gaming characters or intricate visuals, because they mimic hand-drawn objects or sprites. Use third-party tools like Rive or Lottie, which provide high-level interfaces for graphic-based animations that you can integrate into Flutter, if your animation appears more like a stand-alone visual design. However, Flutter's native code-based options might be more appropriate if the animation calls for simple widget modifications. The sets of decisions that you can take to choose you flutter animation are expressed in the decision tree below:

1. Implicit or Explicit Animations?

The dilemma of whether to utilize implicit or explicit animations arises once you decide that your animation will be code-based. Implementing implicit animations is easy because all that is needed is to set a new property value, after which Flutter will automatically animate it from the old value to the updated one. Because of their simplicity and low scripting requirements, these animations are great for novices and work quite well for simple transitions. Explicit animations, on the other hand, offer more control but necessitate a manual animation lifecycle management tool called an AnimationController. Animations that need additional customization, synchronization with other widgets, or continuous behavior—like recurring animations—benefit from this method.

2. Making the Final Widget Selection

It all boils down to determining whether a built-in widget meets your needs before selecting one. Flutter provides a number of widgets for implicit animations, like AnimatedOpacity and AnimatedContainer, which manage typical animation requirements with little setup. Consider using TweenAnimationBuilder to create bespoke implicit animations if the built-in widget is not suitable for your purposes. If they fit your property requirements, search for widgets like SlideTransition or ScaleTransition for explicit animations. If not, using AnimatedBuilder or extending AnimatedWidget would be your best bet if your animation includes intricate or synchronized movements. Additionally, if speed is an issue, think about utilizing CustomPainter to draw straight to the canvas instead of the standard widget structure, which can optimize some animations.

In conclusion, you can choose the best Flutter animation widget for your app with confidence if you follow a methodical process that starts with the animation type, then decides whether implicit or explicit control is required, and ultimately chooses particular widgets. In addition to making development easier, this decision-making process guarantees that your animations are fluid, effective, and consistent with the desired visual experience.

3. Understanding When to Use AnimatedBuilder or AnimatedWidget in Flutter

When you want to animate a complex widget tree or multiple properties in Flutter, the AnimatedBuilder widget is perfect because it allows you to wrap the entire widget tree you want to animate within a builder function, which saves resources by allowing you to make efficient and repeated animations without having to rebuild the tree every time you update a frame. The builder function, which takes the controller values, is only called during animation frames. 

Nonetheless, When the animation logic can be contained in a smaller, more modular widget, the AnimatedWidget class is helpful. By extending AnimatedWidget, you can obtain a clean structure without requiring a separate AnimatedBuilder or complicated build function, which is especially helpful when you want to create a widget that is dedicated to a single animation because it minimizes boilerplate and keeps the code organized. Because it allows you to animate only specified elements of the widget hierarchy, the AnimatedBuilder is very helpful when you need to create intricate animations inside a bigger widget tree. It is the preferred option if your animation uses a lot of widgets or if it would be inefficient to render the entire widget tree again for every frame.

In conclusion, If you require an easily reusable, self-contained animation widget, go with AnimatedWidget. If the functionality of your animation can be condensed into a single, stand-alone widget, AnimatedWidget aids in code organization and modularity. Additionally, this widget can be used for new widgets that extend pre-existing animations or when layering build functions inside of build functions is not desired.

Flutter Animation Basics with Implicit Animations

Flutter's implicit animations offer a quick and easy method of animating widget properties without the need for intricate coding or in-depth animation expertise. By simply adjusting property values, implicitly animated widgets can create fluid and captivating animations by handling transitions automatically. In order to give Flutter apps life, this part delves into the basics of implicit animations, emphasizing the robust AnimatedContainer widget and providing information on how to handle durations, curves, and custom animations.

1. Understanding Implicitly Animated Widgets

Improved versions of ordinary widgets, implicitly animated widgets in Flutter are made to smoothly animate property changes. AnimatedContainer, AnimatedOpacity, and AnimatedPositioned are a few examples. Developers can create seamless transitions with few code modifications by enclosing standard widgets in implicitly animated counterparts. These widgets improve user experience without the hassle of managing animation lifecycles by automatically adjusting between old and new values as properties are altered. For example, the code that follows shows how to simply alter a Container width to make it animated:

@override
Widget build(BuildContext context) {
  return Column(
    mainAxisAlignment: MainAxisAlignment.center,
    children: <Widget>[
      AnimatedContainer(
        width: _bigger ? 100 : 500,
        child: Image.asset('assets/star.png'),
        duration: Duration(seconds: 1),
      ),
      ElevatedButton(
        onPressed: () => setState(() {
          _bigger = !_bigger;
        }),
        child: Icon(Icons.star),
      ),
    ],
  );
}

Here, AnimatedContainer transitions its width over one second, which creates a smooth resizing effect with minimal setup.

2. Using Duration and Curves to Control Animation Flow

The speed and style of transitions can be altered using attributes like duration and curve provided by AnimatedContainer and other implicitly animated widgets. curve uses a mathematical function to alter the transition's feel, while duration determines how long the animation will take to finish. For instance, the animation feels more natural when a quintic curve (Curves.easeInOutQuint) is used, which accelerates at first and slows down as it finishes. Simple changes to these parameters improve the animation's flow and add visual interest:

AnimatedContainer(
  width: _bigger ? 100 : 500,
  child: Image.asset('assets/star.png'),
  duration: Duration(seconds: 1),
  curve: Curves.easeInOutQuint,
),

This code snippet alters the animation's smoothness, and it transforms the transition into a more dynamic experience.

3. Custom Curves for Unique Animation Styles

Custom curves provide additional customization when the default curves are unable to satisfy particular requirements. Curve can be subclassed to allow developers to provide special behaviors. The following SineCurve example uses the sine function to provide a bouncing effect to the animation, creating a rhythmic, oscillating motion:

class SineCurve extends Curve {
  final double count;
 
  SineCurve({this.count = 1});
 
  @override
  double transformInternal(double t) {
    return sin(count * 2 * pi * t) * 0.5 + 0.5;
  }
}

This curve can be used to give an animation a fun, unique touch, making it ideal for applications that want to amuse or visually engage consumers.

4. Recap and Next Steps

Flutter's implicit animations make animation creation easier by automating changes between property values. One notable feature of AnimatedContainer is its adaptability, which enables fluid, editable animations with little coding. By simply altering properties within predetermined durations and curves, widgets like AnimatedOpacity, AnimatedPositioned, and AnimatedPadding also provide simple, aesthetically pleasing transitions. Investigating explicit animations could be helpful for intricate animations or those that require cooperation between several widgets. Deeper customization and fluidity are made possible by Flutter's many animation features, which guarantee a responsive and aesthetically pleasing user experience.

Introduction to Custom Implicit Animations in Flutter

There are multiple ways to implement animations with Flutter, and each is appropriate for a certain situation. For simple, one-widget animations that do not repeat endlessly, TweenAnimationBuilder is especially helpful. In order to demonstrate TweenAnimationBuilder's adaptability and control over animations without requiring AnimationController, this article examines the situations in which it is better than other implicit animation widgets. Here are some real-world instances and how it operates.

1. Setting Up Basic TweenAnimationBuilder

To begin using TweenAnimationBuilder, use the tween argument to define the animation time and the range of values. A snapshot of your animated widget at any given time is provided by the builder function. Here is an example that changes the color of a widget over a predetermined amount of time:

TweenAnimationBuilder(
  tween: ColorTween(begin: Colors.white, end: Colors.red),
  duration: Duration(seconds: 2),
  builder: (_, Color color, __) {
    return Container(
      color: color,
      width: 100,
      height: 100,
    );
  },
)

In this setup, TweenAnimationBuilder interpolates between Colors.white and Colors.red. It smoothly transitions the container’s color over two seconds.

2. In-Depth Example: Animating a Color Filter

Let us make an app that shows how a star's color changes as it moves in space, a phenomenon known as the Doppler effect. We accomplish this by gradually altering the star's color using ColorFiltered with a BlendMode. TweenAnimationBuilder makes it simple to animate between two colors, but Flutter does not include a built-in widget for color filter animations:

TweenAnimationBuilder(
  tween: ColorTween(begin: Colors.white, end: Colors.orange),
  duration: Duration(seconds: 3),
  builder: (_, Color color, __) {
    return ColorFiltered(
      child: Image.asset('assets/star.png'),
      colorFilter: ColorFilter.mode(color, BlendMode.modulate),
    );
  },
)

By nesting ColorFiltered within TweenAnimationBuilder, you animate the star image’s color between white and orange. This simulates the Doppler effect.

3. Dynamic Tweens and Interactive Animations

You may improve interactivity by dynamically updating the animation's end value with TweenAnimationBuilder. Here is an example where users can change the color in real time using a slider to modify the animation's color filter. To guarantee seamless transitions, the animation continually interpolates from the current to the new end value.

double _sliderValue = 0.0;
TweenAnimationBuilder(
  tween: ColorTween(begin: Colors.white, end: Color.lerp(Colors.white, Colors.red, _sliderValue)),
  duration: Duration(milliseconds: 500),
  builder: (_, Color color, __) {
    return ColorFiltered(
      child: Image.asset('assets/star.png'),
      colorFilter: ColorFilter.mode(color, BlendMode.modulate),
    );
  },
)

This example updates ColorTween's end color based on the slider's position. It provides an interactive color animation.

4. Enhancing Animations with Curves and Callbacks

Additionally, TweenAnimationBuilder has a curve parameter that lets you adjust the animation pacing, and the onEnd callback lets you do things like start a new animation or toggle widgets when the animation is finished. If you want an animation that repeats continuously, though, you should think about using explicit animation controls.

TweenAnimationBuilder(
  tween: Tween<double>(begin: 1.0, end: 2.0),
  duration: Duration(seconds: 2),
  curve: Curves.easeInOut,
  onEnd: () {
    // Actions to perform after animation ends
  },
  builder: (_, double scale, __) {
    return Transform.scale(
      scale: scale,
      child: Icon(Icons.star, size: 50),
    );
  },
)

In this example, the scale animation uses Curves.easeInOut for a smooth transition.

5. Optimization with the Child Parameter

Use the child parameter for static content that does not require frame-by-frame rewriting to maximize efficiency. Passing the picture as a child, for example, minimizes rebuilds when animating just the color filter of an image, concentrating only on the filter updates.

TweenAnimationBuilder(
  tween: ColorTween(begin: Colors.white, end: Colors.orange),
  duration: Duration(seconds: 3),
  child: Image.asset('assets/star.png'),
  builder: (_, Color color, child) {
    return ColorFiltered(
      child: child,
      colorFilter: ColorFilter.mode(color, BlendMode.modulate),
    );
  },
)

This ensures the image remains static, improving performance, especially when animating complex widgets.

TweenAnimationBuilder is a powerful tool for creating smooth animations without explicit control; it is perfect for one-time, "set-it-and-forget-it" animations and offers straightforward yet powerful options with dynamic Tweens and performance optimizations. You can easily create captivating animations in Flutter by leveraging the curve and onEnd parameters or by adjusting the end value.

More resources 

Discover more about Flutter animations by looking through the Flutter Sample app catalog, which offers a variety of animation samples for you to study and get ideas from. Additionally, the Flutter YouTube channel offers animation lessons and instructions that include step-by-step walkthroughs and visual explanations. Furthermore, the Flutter API documentation provides a thorough rundown of the animation library, along with examples and comprehensive documentation to help you better grasp how to use animations in Flutter.

Conclusion

In conclusion, mastering Flutter animation necessitates familiarity with a wide range of techniques and materials in order to create compelling and successful user experiences. We began by discussing the basics of motion in Flutter and how animations use fast frame changes to simulate movement. We next looked at the many animation styles that Flutter offers, such as tween-based, physics-based, and pre-canned, and how each satisfies different design specifications. We looked at common UI/UX motion patterns and the Flutter widgets that implement them after establishing that foundation.

Making the right animation widget choice is crucial to optimizing both performance and aesthetic appeal. Regardless of whether you prefer code-based or drawing-based animations, the user experience of your app can be greatly impacted by selecting the appropriate widget, such as the AnimatedBuilder, or third-party tools, such as Rive and Lottie. The flexibility of TweenAnimationBuilder for more complex animations and the simplicity of basic transitions with widgets like AnimatedContainer were highlighted in the discussion about implicit animations. Finally, we examined the adaptability and efficiency of AnimatedBuilder in animating complex widget trees. Flutter developers can create dynamic and fluid animations that enhance the user experience overall if they have the right tools and understand these concepts.