我已经为容器实现了Scale手势。另外,我添加了onHorizontalDragUpdate和onVerticalDragUpdate。但是,当我尝试同时添加两者时,出现了一个异常,说无法同时使用Scale手势实现两者。即使是平移手势,也会引发相同的异常。下面是我的代码:
import 'package:flutter/material.dart';
import 'package:vector_math/vector_math_64.dart' hide Colors;
import 'dart: math' as math;
class HomeScreen extends StatefulWidget {
@override
State<StatefulWidget> createState() {
return HomeState();
}
}
class HomeState extends State<HomeScreen> {
double _scale = 1.0;
double _previousScale;
var yOffset = 400.0;
var xOffset = 50.0;
var rotation = 0.0;
var lastRotation = 0.0;
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.amber,
body: Stack(
children: <Widget>[
stackContainer(),
],
),
);
}
Widget stackContainer() {
return Stack(
children: <Widget>[
Positioned.fromRect(
rect: Rect.fromPoints( Offset(xOffset, yOffset),
Offset(xOffset+250.0, yOffset+100.0)),
child: GestureDetector(
onScaleStart: (scaleDetails) {
_previousScale = _scale;
print(' scaleStarts = ${scaleDetails.focalPoint}');
},
onScaleUpdate: (scaleUpdates){
//ScaleUpdateDetails
rotation += lastRotation - scaleUpdates.rotation;
lastRotation = scaleUpdates.rotation;
print("lastRotation = $lastRotation");
print(' scaleUpdates = ${scaleUpdates.scale} rotation = ${scaleUpdates.rotation}');
setState(() => _scale = _previousScale * scaleUpdates.scale);
},
onScaleEnd: (scaleEndDetails) {
_previousScale = null;
print(' scaleEnds = ${scaleEndDetails.velocity}');
},
child:
Transform(
transform: Matrix4.diagonal3( Vector3(_scale, _scale, _scale))..rotateZ(rotation * math.pi/180.0),
alignment: FractionalOffset.center,
child: Container(
color: Colors.red,
),
)
,
),
),
],
);
}
}
我想在红色子视图中移动并随比例尺旋转。
我们可以使用ScaleUpdateDetails对象的focusPoint字段,该对象在onScaleUpdate函数中作为参数获取。
与上述示例有关的解决方案:我们需要更新onScaleUpdate方法。
onScaleUpdate: (scaleUpdates) {
lastRotation += scaleUpdates.rotation;
var offset = scaleUpdates.focalPoint;
xOffset = offset.dx;
yOffset = offset.dy;
setState(() => _scale = _previousScale * scaleUpdates.scale);
}
在上面的代码中更改Positioned Widget的'rect'字段。
rect: Rect.fromPoints(Offset(xOffset - 125.0, yOffset - 50.0),
Offset(xOffset + 250.0, yOffset + 100.0))
默认GestureRecognizer
不支持对平移/拖动和缩放的识别同时。我认为这是错误,应该修复。要实现这种行为-您需要基于RawGestureDetector
手势构建自己的消雾器ImmediateMultiDragGestureRecognizer
。
我已经在这里实现了PanAndScalingGestureRecognizer
类:https://gist.github.com/comm1x/8ffffd08417053043e079878b4bd8d03
所以您可以看到完整的示例,也可以复制粘贴并使用。