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void _createAnimationIntervals() {
for (var i = 0; i < _menuTitles.length; ++i) {
final startTime = _initialDelayTime + (_staggerTime * i);
final endTime = startTime + _itemSlideTime;
_itemSlideIntervals.add(
Interval(
startTime.inMilliseconds / _animationDuration.inMilliseconds,
endTime.inMilliseconds / _animationDuration.inMilliseconds,
),
);
}
final buttonStartTime =
Duration(milliseconds: (_menuTitles.length * 50)) + _buttonDelayTime;
final buttonEndTime = buttonStartTime + _buttonTime;
_buttonInterval = Interval(
buttonStartTime.inMilliseconds / _animationDuration.inMilliseconds,
buttonEndTime.inMilliseconds / _animationDuration.inMilliseconds,
);
}
}<code_end>
<topic_end>
<topic_start>
Animate the list items and button
The staggered animation plays as soon as the menu becomes visible.Start the animation in initState().
<code_start>@override
void initState() {
super.initState();
_createAnimationIntervals();
_staggeredController = AnimationController(
vsync: this,
duration: _animationDuration,
)..forward();
}<code_end>
Each list item slides from right to left and
fades in at the same time.Use the list item’s Interval and an easeOut
curve to animate the opacity and translation
values for each list item.
<code_start>List<Widget> _buildListItems() {
final listItems = <Widget>[];
for (var i = 0; i < _menuTitles.length; ++i) {
listItems.add(
AnimatedBuilder(
animation: _staggeredController,
builder: (context, child) {
final animationPercent = Curves.easeOut.transform(
_itemSlideIntervals[i].transform(_staggeredController.value),
);
final opacity = animationPercent;
final slideDistance = (1.0 - animationPercent) * 150;
return Opacity(
opacity: opacity,
child: Transform.translate(
offset: Offset(slideDistance, 0),
child: child,
),
);
},
child: Padding(
padding: const EdgeInsets.symmetric(horizontal: 36, vertical: 16),
child: Text(
_menuTitles[i],
textAlign: TextAlign.left,
style: const TextStyle(
fontSize: 24,
fontWeight: FontWeight.w500,
),
),
),
),
);
}
return listItems;
}<code_end>
Use the same approach to animate the opacity and
scale of the bottom button. This time, use an
elasticOut curve to give the button a springy effect.
<code_start>Widget _buildGetStartedButton() {
return SizedBox(
width: double.infinity,
child: Padding(
padding: const EdgeInsets.all(24),
child: AnimatedBuilder(
animation: _staggeredController,
builder: (context, child) {
final animationPercent = Curves.elasticOut.transform(
_buttonInterval.transform(_staggeredController.value));
final opacity = animationPercent.clamp(0.0, 1.0);
final scale = (animationPercent * 0.5) + 0.5;
return Opacity(
opacity: opacity,
child: Transform.scale(
scale: scale,
child: child,
),
);
},
child: ElevatedButton(
style: ElevatedButton.styleFrom(
shape: const StadiumBorder(),
backgroundColor: Colors.blue,