My goal is, to have a container who can be dragged around in the vertical axis. After removing the finger the container should move a bit forward with the velocity I had after ending the touch. I want to have the exact same animation/feeling after you stop scrolling on an android phone and it continues to scroll a little bit further.
This is what it looks so far:
This is my code:
class _MyHomePageState extends State<MyHomePage>
with SingleTickerProviderStateMixin {
double _offeset = 0;
double get offset => _offeset;
set offset(double offeset) {
if(offeset < 500)
setState(() {
_offeset = offeset;
});
}
AnimationController controller;
ClampingScrollSimulation simulation;
#override
void initState() {
super.initState();
controller = AnimationController(vsync: this, upperBound: 5)
..addListener(() {
offset += controller.value;
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: Stack(
children: <Widget>[
Positioned(
top: offset,
left: 0,
right: 0,
child: GestureDetector(
onVerticalDragUpdate: (DragUpdateDetails details) {
offset += details.delta.dy;
},
onVerticalDragEnd: (DragEndDetails details) {
simulation = ClampingScrollSimulation(
position: 0, velocity: details.primaryVelocity,
);
controller.animateWith(simulation);
},
child: Container(height: 50, width: 50, color: Colors.red),
),
),
],
),
);
}
}
The problem is, that this is not the Android scroll animation and I don't know how to get it. (It feels like the animation is linear, stops too early and doesn't take advantage of the velocity parameter) I am even using the ClampingScrollSimulation class, which is used in all Scroll widgets in Flutter to simulate Android scrolling.
The solution was to multiply the _controller.value with _controller.velocity. Like this:
offset += controller.value * _controller.velocity / 100;
Related
I have a grid of cards depicting products. When a card is tapped, I want it to flip over (around the Y axis) to reveal the "other side" that shows the details, while simultaneously growing to fill the screen.
Duration 0.0 - Card shows front side and is in grid view
Duration 0.5 - Card is 50% of the way to full-screen and perpendicular to the screen (front side facing to the right, "back" side facing to the left)
Duration 1.0 - Card is fully expanded and the "back" card is showing.
I have managed to get a flip animation working, but am having trouble figuring out how to also get it to run during the Hero transition. From this article it seems like I may need to make use of flightShuttleBuilder to be able to animate the overlay but my animation does not run during the transition:
return Hero(
tag: 'test',
flightShuttleBuilder: (
BuildContext flightContext,
Animation<double> animation,
HeroFlightDirection flightDirection,
BuildContext fromHeroContext,
BuildContext toHeroContext,
) {
final Hero toHero = toHeroContext.widget;
return Transform(
transform: Matrix4.identity()..rotateY(-pi * animation.value),
alignment: FractionalOffset.center,
child: toHero,
);
},
child: Card(...),
);
As it turns out, flightShuttleBuilder only emits values at the start and end of the transition instead of throughout the animation. Capturing from this issue on GitHub, it is apparently expected behavior.
The workaround is to create your own transition which extends from AnimatedWidget; that will emit values normally and can be used in the flightShuttleBuilder:
class FlipcardTransition extends AnimatedWidget {
final Animation<double> flipAnim;
final Widget child;
FlipcardTransition({#required this.flipAnim, #required this.child})
: assert(flipAnim != null),
assert(child != null),
super(listenable: flipAnim);
#override
Widget build(BuildContext context) {
return Transform(
transform: Matrix4.identity()
..rotateY(-pi * flipAnim.value),
alignment: FractionalOffset.center,
child: child,
);
}
}
...
flightShuttleBuilder: (BuildContext flightContext,
Animation<double> animation,
HeroFlightDirection flightDirection,
BuildContext fromHeroContext,
BuildContext toHeroContext,) {
final Hero toHero = toHeroContext.widget;
return FlipcardTransition(
flipAnim: animation,
child: toHero,
);
},
As Matt said, the default behavior is only emitting start and end value, so we should listen the animation to get the full animatable widget. Here is an example:
Hero(
tag: "YourHeroTag",
flightShuttleBuilder: (BuildContext flightContext,
Animation<double> animation,
HeroFlightDirection flightDirection,
BuildContext fromHeroContext,
BuildContext toHeroContext,) {
return AnimatedBuilder(
animation: animation,
builder: (context, value) {
return Container(
color: Color.lerp(Colors.white, Colors.black87, animation.value),
);
},
);
},
child: Material( // Wrap in Material to prevent missing theme, mediaquery, ... features....
// ...
)
)
It's recommended to wrap in Material widget to prevent unexpected missing style.
So I'm trying to create an animation in Flutter that requires a different outcome every time the user presses a button.
I've implemented the following code according to the Flutter Animations tutorial and created a function to update it.
class _RoulettePageWidgetState extends State<RoulettePageWidget>
with SingleTickerProviderStateMixin {
Animation<double> _animation;
Tween<double> _tween;
AnimationController _animationController;
int position = 0;
#override
void initState() {
super.initState();
_animationController =
AnimationController(duration: Duration(seconds: 2), vsync: this);
_tween = Tween(begin: 0.0, end: 100.0);
_animation = _tween.animate(_animationController)
..addListener(() {
setState(() {});
});
}
void setNewPosition(int newPosition) {
_tween = Tween(
begin: 0.0,
end: math.pi*2/25*newPosition);
_animationController.reset();
_tween.animate(_animationController);
_animationController.forward();
}
#override
Widget build(BuildContext context) {
return Container(
child: Column(
children: <Widget>[
Center(
child: Transform.rotate(
angle: _animationController.value,
child: Icon(
Icons.arrow_upward,
size: 250.0,
),
)),
Expanded(
child: Container(),
),
RaisedButton(
child: Text('SPIN'),
onPressed: () {
setState(() {
setNewPosition(math.Random().nextInt(25));
});
},
)
],
)
);
}
}
As you can see I'm updating the _tween's begin: and end: but this doesn't seem to change the animation.
So what should I be doing to create a 'different' animation every time the users presses the button?
The general idea is to make the animations build upon each other with a random new value so for example:
first spin: 0 -> 10
second spin: 10 -> 13
third spin: 13 -> 18
... etc
So I wondered if I could update the animation, or should I create a new animation every time?
Another thing I could think of was tracking the positions and use the same animation every time (0.0 -> 100.0) to act as a percentage of the transfer.
So instead of creating a new animation from 10 -> 15 I would be doing something like:
currentValue = 10 + (15-10)/100*_animationController.value
I'm going to skip your code a bit, and focus on what you're really asking:
The general idea is to make the animations build upon each other with a random new value so for example:
first spin: 0 -> 10
second spin: 10 -> 13
third spin: 13 -> 18
... etc
With an explicit animation like this, there are three objects you are interested in:
a controller, which is a special kind of Animation that simply generates values linearly from its lower to its upper bound (both doubles, typically 0.0 and 1.0). You can control the flow of the animation - send it running forward, reverse it, stop it, or reset it.
a tween, which isn't an Animation but rather an Animatable. A tween defines the interpolation between two values, which don't even have to be numbers. It implements a transform method under the hood that takes in the current value of an animation and spits out the actual value you want to work with: another number, a color, a linear gradient, even a whole widget. This is what you should use to generate your angles of rotation.
an animation, which is the animation whose value you're actually going to work with (so this is where you'd grab values to build with). You get this by giving your tween a parent Animation to transform - this might be your controller directly but can also be some other sort of animation you've built on it (like a CurvedAnimation, which would give you easing or bouncy/elastic curves and so on). Flutter's animations are highly composable that way.
Your code is failing largely because you're not actually using the top-level animation you created in your build method and you're creating a new tween and animation every time you call setNewPosition. You can use the same tween and animation for multiple animation "cycles" - simply change the begin and end properties of the existing tween and it bubbles up to the animation. That ends up something like this:
class _RoulettePageWidgetState extends State<RoulettePageWidget>
with SingleTickerProviderStateMixin {
Animation<double> _animation;
Tween<double> _tween;
AnimationController _animationController;
math.Random _random = math.Random();
int position = 0;
double getRandomAngle() {
return math.pi * 2 / 25 * _random.nextInt(25);
}
#override
void initState() {
super.initState();
_animationController =
AnimationController(duration: Duration(seconds: 2), vsync: this);
_tween = Tween(begin: 0.0, end: getRandomAngle());
_animation = _tween.animate(_animationController)
..addListener(() {
setState(() {});
});
}
void setNewPosition() {
_tween.begin = _tween.end;
_animationController.reset();
_tween.end = getRandomAngle();
_animationController.forward();
}
#override
Widget build(BuildContext context) {
return Container(
child: Column(
children: <Widget>[
Center(
child: Transform.rotate(
angle: _animation.value,
child: Icon(
Icons.arrow_upward,
size: 250.0,
),
)),
Expanded(
child: Container(),
),
RaisedButton(
child: Text('SPIN'),
onPressed: setNewPosition,
)
],
)
);
}
}
Hope that helps!
While working, in no situation will you actually want to make these animations within your layout as explained by #filleduchaos.
This is under optimized, as you're rebuilding far more than you should for the animation. And it's a pain to write yourself.
You'll want to use the AnimatedWidget family for this. They are divided into two
kinds:
XXTransition
AnimatedXX
The first is a low layer that consumes an Animation and listens to it so that you don't need to do that ugly :
..addListener(() {
setState(() {});
});
The second handles the remaining pieces: AnimationController, TickerProvider and Tween.
This makes using animations much easier as it's almost entirely automatical.
In your case a rotation example would be as followed:
class RotationExample extends StatefulWidget {
final Widget child;
const RotationExample({
Key key,
this.child,
}) : super(key: key);
#override
RotationExampleState createState() {
return new RotationExampleState();
}
}
class RotationExampleState extends State<RotationExample> {
final _random = math.Random();
double rad = 0.0;
#override
Widget build(BuildContext context) {
return GestureDetector(
onTap: _rotate,
child: AnimatedTransform(
duration: const Duration(seconds: 1),
alignment: Alignment.center,
transform: Matrix4.rotationZ(rad),
child: Container(
color: Colors.red,
height: 42.0,
width: 42.0,
),
),
);
}
void _rotate() {
setState(() {
rad = math.pi * 2 / 25 * _random.nextInt(25);
});
}
}
Easier right?
The irony is that Flutter forgot to provide an AnimatedTransform (even although we have many others !). But no worries, I made it for you!
The AnimatedTransform implementation is as followed :
class AnimatedTransform extends ImplicitlyAnimatedWidget {
final Matrix4 transform;
final AlignmentGeometry alignment;
final bool transformHitTests;
final Offset origin;
final Widget child;
const AnimatedTransform({
Key key,
#required this.transform,
#required Duration duration,
this.alignment,
this.transformHitTests = true,
this.origin,
this.child,
Curve curve = Curves.linear,
}) : assert(transform != null),
assert(duration != null),
super(
key: key,
duration: duration,
curve: curve,
);
#override
_AnimatedTransformState createState() => _AnimatedTransformState();
}
class _AnimatedTransformState
extends AnimatedWidgetBaseState<AnimatedTransform> {
Matrix4Tween _transform;
#override
void forEachTween(TweenVisitor<dynamic> visitor) {
_transform = visitor(_transform, widget.transform,
(dynamic value) => Matrix4Tween(begin: value));
}
#override
Widget build(BuildContext context) {
return Transform(
alignment: widget.alignment,
transform: _transform.evaluate(animation),
transformHitTests: widget.transformHitTests,
origin: widget.origin,
child: widget.child,
);
}
}
I will submit a pull request so that in the future you won't need this bit of code.
If you want to reverse your animation with a different path (go/back way). Try this.
In your setNewPosition function, just define new begin/end value for _tween.
void setNewPosition() {
_tween.begin = 0; //new begin int value
_tween.end = 1; //new end int value
_animationController.reverse();
}
So I'm trying to create a trivial slide transition element in flutter and I'm having some difficulty. What the below does is wait for the animation time, and then just display the Text("hello there sailor"). I don't know why this is not animating - it seems very similar to this previous post that has a trivial example (Sliding animation to bottom in flutter).
This is how I call the below code: DeleteCheck(offsetBool: widget.model.deleteNotify, widthSlide: 0.50*width100) where double width100 = MediaQuery.of(context).size.width;.
Does anyone see what I am doing wrong?
class DeleteCheck extends StatefulWidget{
final offsetBool;
final double widthSlide;
DeleteCheck({
Key key,
this.offsetBool,
this.widthSlide
}): super(key: key);
#override
State<StatefulWidget> createState() {
return new _MyDeleteCheck();
}
}
class _MyDeleteCheck extends State<DeleteCheck> with TickerProviderStateMixin {
AnimationController _controller;
Animation<Offset> _offsetFloat;
#override
void initState() {
super.initState();
_controller = AnimationController(
vsync: this,
duration: const Duration(seconds: 1),
);
_offsetFloat = Tween<Offset>(begin: Offset(widget.widthSlide, 0.0), end: Offset.zero)
.animate(_controller);
_offsetFloat.addListener((){
setState((){});
});
_controller.forward();
}
#override
void dispose() {
_controller.dispose();
super.dispose();
}
#override
Widget build(BuildContext context) {
double height100 = MediaQuery.of(context).size.height;
double width100 = MediaQuery.of(context).size.width;
return new SlideTransition(
position: _offsetFloat,
child: Container(
color: Colors.cyan,
width: 0.525*width100-3.0,
child: Text("hello there sailor")
)
);
}
}
I have good news for you! Your code is working! :) The animation looks like it is not happening, because the distance it moves is huge. The Offset, passed to the SlideTransition, is relative to its childs size. For example your child has width: 100.0 and you offset with Offset(2.0, 0.0), your child will have moved 200.0 pixels to the right.
Just try to
change begin: Offset(widget.widthSlide, 0.0), end: Offset.zero
to begin: Offset(2.0, 0.0), end: Offset.zero. You'll see the text slowly animating from the right to the center of the screen. Therefore you just need to adjust your parameterisation.
Anyway here are some additional suggestions for optimizing your code:
If you are using prebuilt AnimatedWidgets like the SlideTransition, you do not need to call addListener with setState on the controller. The AnimatedWidget takes care of it by itself. Hence you can remove the follwing lines:
lines:
_offsetFloat.addListener((){
setState((){});
});
Also it is not necessary to call const constructors. You can just leave this keyword out like new. The compiler will optimize and choose the right constructor in each case.
I'm trying to create a dynamic animation described in the mockup above. What I need is:
A round shape that will represent an avatar (user pic, for example);
A text centered below it.
Below those (that use half of the screen) is a scrollable PageView.
The animation should be as the following:
Begin: In a Stack both centered at the begin.
Animation: Scaling down and sliding the text (with variable lenght) that must be to the right of the avatar.
End: As the second image in the mockup. Side-to-side while the content below keeps scrolling.
Thought in SliverPersistentHeader combined with CustomMultiChildLayout but the problem is that the text starts centered and ends align to the left and I can animate this dynamically. I was trying to remove the offset of the centered text in the end but it doesn't feel right.
Any help or a sample only with this animation would be appreciate. Thank you.
You will need a Sliver to animate your layout based on the scroll offset. More specifically, SliverPersistentHeader in your situation.
CustomMultiChildLayout is not necessary though, you can achieve the same result using tweens and align/padding/stuff. But you can give it a go if your layout starts to become too complex.
The trick is to use the scroll offset given by SliverPersistentHeader to compute the current progression. Then use that progression to position element between their original and final position.
Here's a raw example:
class TransitionAppBar extends StatelessWidget {
final Widget avatar;
final Widget title;
const TransitionAppBar({this.avatar, this.title, Key key}) : super(key: key);
#override
Widget build(BuildContext context) {
return SliverPersistentHeader(
pinned: true,
delegate: _TransitionAppBarDelegate(
avatar: avatar,
title: title,
),
);
}
}
class _TransitionAppBarDelegate extends SliverPersistentHeaderDelegate {
final _avatarTween =
SizeTween(begin: Size(150.0, 150.0), end: Size(50.0, 50.0));
final _avatarMarginTween =
EdgeInsetsTween(begin: EdgeInsets.zero, end: EdgeInsets.only(left: 10.0));
final _avatarAlignTween =
AlignmentTween(begin: Alignment.topCenter, end: Alignment.centerLeft);
final _titleMarginTween = EdgeInsetsTween(
begin: EdgeInsets.only(top: 150.0 + 5.0),
end: EdgeInsets.only(left: 10.0 + 50.0 + 5.0));
final _titleAlignTween =
AlignmentTween(begin: Alignment.center, end: Alignment.centerLeft);
final Widget avatar;
final Widget title;
_TransitionAppBarDelegate({this.avatar, this.title})
: assert(avatar != null),
assert(title != null);
#override
Widget build(
BuildContext context, double shrinkOffset, bool overlapsContent) {
final progress = shrinkOffset / 200.0;
final avatarSize = _avatarTween.lerp(progress);
final avatarMargin = _avatarMarginTween.lerp(progress);
final avatarAlign = _avatarAlignTween.lerp(progress);
final titleMargin = _titleMarginTween.lerp(progress);
final titleAlign = _titleAlignTween.lerp(progress);
return Stack(
fit: StackFit.expand,
children: <Widget>[
Padding(
padding: avatarMargin,
child: Align(
alignment: avatarAlign,
child: SizedBox.fromSize(size: avatarSize, child: avatar),
),
),
Padding(
padding: titleMargin,
child: Align(
alignment: titleAlign,
child: DefaultTextStyle(
style: Theme.of(context).textTheme.title, child: title),
),
)
],
);
}
#override
double get maxExtent => 200.0;
#override
double get minExtent => 100.0;
#override
bool shouldRebuild(_TransitionAppBarDelegate oldDelegate) {
return avatar != oldDelegate.avatar || title != oldDelegate.title;
}
}
which you can use with a CustomScrollView:
Scaffold(
body: CustomScrollView(
slivers: <Widget>[
TransitionAppBar(
avatar: Material(
color: Colors.blue,
elevation: 3.0,
),
title: Text("Hello World"),
),
SliverList(
delegate: SliverChildBuilderDelegate((context, index) {
return ListTile(
title: Text('$index'),
);
}),
)
],
),
);
I have the following code in place to animate a Positioned widgets, position, when a pan ends. However, it doesn't animate.
Initialising AnimationController and variables:
AnimationController nodesListAnimationController;
Animation<double> nodesListAnimation;
double nodesListOffsetY = 0.0; //widget default offset (will be large, but acts like 0.0)
double nodesListDragOffsetY = 0.0; //how far we have moved the widget from default offset (nodesListOffsetY)
double nodesListTouchOffset = 0.0; //the initial touch when drag begins
final double nodesListHeight = 350.0; //widget height
#override
void initState() {
super.initState();
nodesListAnimationController = AnimationController(
vsync: this,
duration: const Duration(milliseconds: 350),
)
..addListener((){
setState(() {
});
});
}
Build function; See the Positioned widget. I can drag this up and down within the bound I have created using the panning callbacks on GestureDetector.
When the pan ends, I want to animate the Positioned widget back to a given position. Currently, no animation occurs.
#override
Widget build(BuildContext context) {
nodesListOffsetY = MediaQuery.of(context).size.width + 110.0;
AppBar appBar = AppBar(
...
);
return Scaffold(
appBar: appBar,
backgroundColor: Colors.black,
body: Stack(
children: <Widget>[
Column(
children: <Widget>[
cameraWidget(),
cameraControls(),
],
),
Positioned(
left: 0.0,
top: nodesListAnimationController.isAnimating ? nodesListAnimation.value : nodesListOffsetY + nodesListDragOffsetY,
width: MediaQuery.of(context).size.width,
height: nodesListHeight,
child: GestureDetector(
onPanStart: (dragDetails) {
nodesListTouchOffset = (dragDetails.globalPosition.dy - appBar.preferredSize.height) - nodesListOffsetY - nodesListDragOffsetY;
},
onPanUpdate: (dragDetails) {
setState(() {
double newDragOffset = (dragDetails.globalPosition.dy - nodesListOffsetY) - appBar.preferredSize.height - nodesListTouchOffset;
//allow it only to move up if is clips off screen, otherwise upper limit not needed
double nodesListVisible = ((MediaQuery.of(context).size.height - appBar.preferredSize.height) - nodesListOffsetY);
bool isClipping = nodesListVisible < nodesListHeight ? true : false;
double upperLimit = 0.0;
if (isClipping) upperLimit = -(nodesListHeight - nodesListVisible);
//limit drag bounds. don't drag too high or low.
if (newDragOffset < upperLimit) newDragOffset = upperLimit;
else if (newDragOffset > 0) newDragOffset = 0.0;
else nodesListDragOffsetY = newDragOffset;
});
},
onPanEnd: (dragDetails) {
double currentPos = (nodesListOffsetY + nodesListDragOffsetY);
nodesListAnimation = Tween(begin: currentPos, end: nodesListOffsetY).animate(nodesListAnimationController);
nodesListAnimationController.forward(from: currentPos);
nodesListAnimation.addStatusListener((state) {
print(nodesListAnimation.value);
});
},
child: nodesList(),
),
),
],
));
}
Late to the party, but your issue is because of:
nodesListAnimationController.forward(from: currentPos)
Whose from is incorrectly accepting a value outside of 0.0-1.0. So you should probably change it to just controller.forward()
This isn’t well documented, but forward’s from is meant to accept values from 0.0-1.0, or more specifically, if set, then the range provided by lowerBound and upperBound (with few exceptions). (you can also think of it as 0-100%). It is not meant to accept the value range from the Tween’s begin and end, nor is it aware of that range.
https://api.flutter.dev/flutter/animation/AnimationController-class.html
By default, an AnimationController linearly produces values that range from 0.0 to 1.0
https://flutter.dev/docs/development/ui/animations/overview#addstatuslistener
An animation might then run forward (e.g., from 0.0 to 1.0)
(And I can verify that after I changed your code to use just .forward(), I was able to see it animate)