(1) Optionally you can set the initialValue, lowerBound, upperBound to be taken by the AnimationController.
(2) duration and reverseDuration are the global (default) durations of the animation in the forward and reverse path. If reverseDuration is not set (or is null) the value of duration will be used for both forward and reverse path. The value of duration and reverseDuration can be overridden for any value. (see later).
(3) curve and reverseCurve are the global (default) curves of the animation in the forward and reverse path. If reverseCurve is not set (or is null) the value of curve will be used for both forward and reverse path. The value of curve and reverseCurve can be overridden for any value. (see later).
(4) animationBehavior has similar meaning as in Flutter animationBehavior (The behavior of the controller when AccessibilityFeatures.disableAnimations is true).
With cycles argument (5) you define the number of the forward and backward periods you want your animation to perform before stopping.
With repeats argument (5) you define the number of forward periods you want your animation to perform before stopping.
With endAnimationListener (6) argument you can define a VoidCallback to be executed when the animation is finished. For example, it can be used to trigger another animation.
You can control when animation starts (7) using :
triggerOnInt: When set to true, animation will auto start after first initialized. The default value is true.
triggerOnRebuild: When set to true, animation will try to trigger on rebuild. If animation is completed (stopped at the upperBound) then the animation is reversed, and if the animation is dismissed (stopped at the lowerBound) then the animation is forwarded. IF animation is running nothing will happen. Default value is false.
resetOnRebuild: When set to true, animation will reset and restart from its lowerBound.
In the builder argument (8) you put your widgets to be animated.
AnimateWidget(
builder : (BuildContext context, Animate animate) {
//Implicit animationfinal T value = animate.call(select? 0 : 100);
///Two value of the same type must be distinguished using an arbitrary namefinal T otherValue = animate.call(select? 0 : 100, 'Other value');
//Explicit animationfinal T value = animate.fromTween((currentValue)=> Tween(begin:0, end: 100));
//Use predefined flutter FooTransition widgetScaleTransition(
scale : animate.curvedAnimation
child: ...
)
},
child : MayWidget(), //widget to not rebuild with animation
)
Implicit animation
With animator you can do any kind of implicit animation without been constrained to fined a dedicated Flutter widget of type AnimatedFoo such as AnimatedContainer, AnimatedPositioned and so on.
Let's reproduce the AnimatedContainer example in official Flutter docs. (link here).
Using the exposed animate function, we set the animation start and end values.
As the width and height are the same type (double), we need to add a name to distinguish them.
You can implicitly animate any type. Here we implicitly animated a double, Color, and Alignment values. If you want to animate two parameters of the same type, you just add a dummy name to distinguish them.
That's all, you are not limited to use a widget that starts with Animated prefix to use implicit animation.
To implement any type of animation with animator you have to define a Tween (1), Duration (2), and Curve (3). `
With cycles argument (4) you define the number of the forward and backward periods you want your animation to perform before stopping.
With repeats argument (5) you define the number of forward periods you want your animation to perform before stopping.
In the builder argument (6) you put your widgets to be animated.
Animator<T>(
builder : (BuildContext context, AnimatorState animatorState, Widget child) {
//to get animation value:final T value = animatorState.value;
//to get Animation object:finalAnimation<T> animation = animatorState.animation;
//to get AnimationController object:finalAnimationController animation = animatorState.controller;
//to get animation value form tweenMapfinal R value = animatorState.getValue<R>('animName');
//To get Animation object from tweenMapfinalAnimation<R> value =animatorState.getAnimation<R>('animName');
},
child : MayWidget(), //widget to not rebuild with animation
)
If you want to animate many Tween, use tweenMap argument (2). It is a Map of String type keys and Tween type values.
With endAnimationListener (8) argument you can define a VoidCallback to be executed when the animation is finished. For example, it can be used to trigger another animation.
With customListener (9) argument you can define a function to be called every time the animation value changes. The customListener is provided with an Animation object.
With statusListener (10) argument, you can define a function to be called every time the status of the animation change. The customListener is provided with an AnimationStatus, AnimationSetup objects.
triggerOnInit (11) controls whether the animation is automatically started when the Animator widget is initialized. The default value is true.
If you want to reset your animation, such as changing your Tween or duration, and want the new setting to be reconsidered when the Animator widget is rebuilt, set the resetAnimationOnRebuild (12) argument to true. The default value is false. (See AnimatorKey)
The right TickerProvider is chosen by animator:(13)
If animation is simple the singleTickerProviderStateMixin.
If you define the animatorKey parameter or set resetAnimationOnRebuild, animator use tickerProviderStateMixin.
With animationKey (14), you can associate an Animator widget to an AnimatorKey. Doing so, you can control (forward, start, stop, reverse) animation from callbacks outside the Animator widget, you can even reset the animation parameter (tween, duration curve, repeats, cycles) on the fly. (See example below)
Use nested Animators with CustomPainter and CustomClipper and draw the animation you want.
AnimatorKey
Similarly to Flutter global key. AnimatorKey allows controlling the animation from outside the Animator widget it is associated with.
Example:
final animatorKey = AnimatorKey();
//..//..Animator(
animatorKey: animatorKey,
builder: (context, anim, child) {
//....
}
)
//By default, the animation will not start when the Animator is inserted in the widget tree.//To start the animation from some Button in the widget tree outside the builder of the Animator.
onPressed: (){
animatorKey.triggerAnimation();
//You can forward, start, reverse animation
animatorKey.controller.stop,
//You can configure the animation online and reset the setting and restart the animation
animatorKey.refreshAnimation(
tween: Tween(...),//new tween
duration : Duration(...),
curve : Curve(...),
repeats : ....,
cycles : ...
);
}
AnimatorRebuilder widget
The AnimatorRebuilder widget can subscribe to an “AnimatorKey”. It will be animated in synchronization with the Animator widget with which animatorKey is associated.
Example:
//In AnimatorKey you can provide the initial values of the animation.final animatorKey = AnimatorKey<T>(initialValue: 10);
//..//..Animator(
animatorKey: animatorKey,
builder: (context, anim, child) {
//....
}
);
////In another place in the widget tree : AnimatorRebuilder(
observe:()=> animatorKey,
builder: (context, anim, child) {
//....//this widget receives the same animation object of the Animator above.
}
);
The order of Animator and AnimatorRebuilder in the widget tree is irrelevant, except in the case, AnimatorRebuilder is first inserted in the widget tree, you have to provide initial values in AnimatorKey to avoid null exceptions.
