如何从外部小部件访问内部控件的动画控制器(或状态)？

Question

所以我一直在试验Flutter&过去几天的飞镖。我在这个问题上已经坚持了一天多了，所以我来了。

所以我有一个AlarmScreen，里面有两个对象。一个是DraggableMoonWidget；另一个是RisingSunWidget。

目前，RisingSunWidget从底部在屏幕上设置动画，而DraggableMoonWidget可以通过触摸拖动。

我想要实现的是，当RisingSunWidget的动画在拖动DraggableMoonWidget时停止并更改。所以我已经有了MoonDragListener并在工作，但我仍然无法理解。(当前将侦听器调用回AlarmScreen，但随后会怎样？)

我尝试了一大堆方法来做到这一点，从那以后都被删除了，因为没有一个有效。

TLDR当用户触摸DraggableMoonWidget时，我如何控制RisingSunWidget的动画控制器，例如，我想停止控制器并将其动画化到不同的点。

飞镖/扑动的最佳方法是什么？

报警屏幕

import 'package:flutter/widgets.dart';
import 'package:moonworshiper_app/backgrounds.dart';
import 'package:moonworshiper_app/ui/alarm/moon_draggable.dart';
import 'package:moonworshiper_app/ui/alarm/rising_sun.dart';
class AlarmScreen extends StatefulWidget {
@override
State<StatefulWidget> createState() {
return new _AlarmScreenState();
}
}
class _AlarmScreenState extends State<AlarmScreen> {
bool _moonWasTouched = false;
@override
void initState() {
super.initState();
}
@override
Widget build(BuildContext context) {
return new Stack(
children: <Widget>[
new DraggableMoonWidget(new MoonDragListener(this)),
new LayoutBuilder(
builder: (BuildContext context, BoxConstraints constraints) {
return new RisingSunWidget(constraints.heightConstraints().maxHeight, _moonWasTouched);
})
],
);
}
void _refreshSun() {
setState(() {
_moonWasTouched = true;
});
}
}
class MoonDragListener {
_AlarmScreenState state;
MoonDragListener(this.state);
void onMoonDragStarted() {
state._refreshSun();
}
}

DraggableMoonWidget

import 'package:flutter/widgets.dart';
import 'package:moonworshiper_app/ui/alarm/alarm_screen.dart';
class DraggableMoonWidget extends StatefulWidget {
final MoonDragListener moonStartListener;
DraggableMoonWidget(this.moonStartListener);
State<StatefulWidget> createState() => new _DraggableMoonState();
}
class _DraggableMoonState extends State<DraggableMoonWidget>
with TickerProviderStateMixin {

final moonDragTween = new Tween<Offset>(
begin: new Offset(0.0, -0.5),
end: new Offset(0.0, 0.5),
);
var moonAnimListener;
AnimationController _animationController;
Animation<Offset> _dragAnimation;
AnimationController _dragAnimationController;
bool isFirstDraw = true;
@override
initState() {
super.initState();
_animationController = new AnimationController(
vsync: this,
duration: const Duration(milliseconds: 3000),
);
_dragAnimationController = new AnimationController(vsync: this);
moonAnimListener = (AnimationStatus status) {
if (status == AnimationStatus.dismissed) {
_animationController.forward();
} else if (status == AnimationStatus.completed) {
_animationController.reverse();
} else if (status == AnimationStatus.forward) {}
};
_dragAnimation = moonDragTween.animate(new CurvedAnimation(
parent: _dragAnimationController,
curve: Curves.easeInOut,
reverseCurve: Curves.easeInOut));
_dragAnimationController.animateTo(0.5, duration: new Duration());

_animationController.addStatusListener(moonAnimListener);

_animationController.forward();
}
@override
Widget build(BuildContext context) {
return new Container(
child: new Center(
child: new SlideTransition(
position: _dragAnimation,
child: new GestureDetector(
child: new Image.asset(
"assets/moon.png",
width: 280.0,
height: 280.0,
),
onVerticalDragStart: (DragStartDetails details) {
print("start:" + details.globalPosition.toString());
_animationController.removeStatusListener(moonAnimListener);
_animationController.stop();
_dragStartDetails = details;
_dragAnimationController.animateTo(0.5,
duration: new Duration(milliseconds: 50));
if (isFirstDraw) {
isFirstDraw = false;
widget.moonStartListener.onMoonDragStarted();
}
},
),
),
),
//      margin: new EdgeInsets.only(top: 48.0),
);
}
@override
void dispose() {
_animationController.dispose();
super.dispose();
}
}

RisingSunWidget

import 'package:flutter/widgets.dart';
class RisingSunWidget extends StatefulWidget {
// needed to calculate the offset map
final double screenHeight;
// that's how we know if the use touched the moon
final bool moonWasTouched;
RisingSunWidget(this.screenHeight, this.moonWasTouched);
@override
State<StatefulWidget> createState() {
return new RisingSunState();
}
}
class RisingSunState extends State<RisingSunWidget> with TickerProviderStateMixin {
AnimationController _animationController;
Animation<Offset> _sunAnimation;
final double sunSize = 320.0;
@override
initState() {
super.initState();
_animationController = new AnimationController(
vsync: this,
duration: const Duration(milliseconds: 6000),
);
// how many suns fit in the height of our screen
assert(widget.screenHeight > sunSize);
double sunsInHeight = widget.screenHeight / sunSize;
print(sunsInHeight.toString() + " suns could fit on the user's screen");
var sunsPlusMargins = sunsInHeight + 1; // required margins
final moonTween = new Tween<Offset>(
begin: new Offset(0.0, -0.5 * sunsPlusMargins),
end: new Offset(0.0, 0.5 * sunsPlusMargins), //move by 8% of height max
);
_sunAnimation = moonTween.animate(new CurvedAnimation(
parent: _animationController,
curve: Curves.easeInOut,
reverseCurve: Curves.easeInOut,
));

if (widget.moonWasTouched) {
_animationController.stop();
_animationController.animateTo(0.68,
duration: new Duration(milliseconds: 2000));
} else {
_animationController.animateTo(0.88,
duration: new Duration(milliseconds: 0));
_animationController.animateTo(0.75,
duration: new Duration(milliseconds: 15000));
}
}
@override
Widget build(BuildContext context) {
return new Center(
child: new SlideTransition(
position: _sunAnimation,
child: new Image.asset(
"assets/sun.png",
width: sunSize,
height: sunSize,
),
),
);
}
@override
void dispose() {
_animationController.dispose();
super.dispose();
}

}

Answer 1

2种可能性：

• 使用构建方法中提供的BuildContext context。BuildContext有一些方法可以获取特定类型的最近父级
• 将key属性传递给所需的小部件。确切地说是CCD_ 4。GlobalKey允许您直接访问Widget或其状态