我想知道是否有一种方法可以在 Flutter 中创建具有渐变颜色的滑块小部件。 Here是滑块类的链接,但没有“SliderTheme”或类似的东西。
我现在基于 this youtube 视频创建了一个自定义轨道形状类,并在构造函数中添加了渐变属性。
渐变:
LinearGradient gradient = LinearGradient(
colors: <Color> [
Colors.red,
Colors.orange,
Colors.yellow,
Colors.green,
Colors.blue,
Colors.blue[900],
Colors.purple
]
);
滑块:
(属性 darkenInactive = false 用于不使非活动侧的滑块变暗。)
SliderTheme(
data: SliderThemeData(
trackShape: GradientRectSliderTrackShape(gradient: gradient, darkenInactive: false),
),
child: Slider(
min: 0,
max: 10,
value: value,
onChanged: (double value) {},
)
),
形状类:
import 'package:flutter/material.dart';
/// Based on https://www.youtube.com/watch?v=Wl4F5V6BoJw
class GradientRectSliderTrackShape extends SliderTrackShape
with BaseSliderTrackShape {
const GradientRectSliderTrackShape({
this.gradient = const LinearGradient(
colors: [
Colors.red,
Colors.yellow,
],
),
this.darkenInactive = true,
});
final LinearGradient gradient;
final bool darkenInactive;
@override
void paint(
PaintingContext context,
Offset offset,
{
required RenderBox parentBox,
required SliderThemeData sliderTheme,
required Animation<double> enableAnimation,
required TextDirection textDirection,
required Offset thumbCenter,
bool isDiscrete = false,
bool isEnabled = false,
double additionalActiveTrackHeight = 2,
}
) {
assert(sliderTheme.disabledActiveTrackColor != null);
assert(sliderTheme.disabledInactiveTrackColor != null);
assert(sliderTheme.activeTrackColor != null);
assert(sliderTheme.inactiveTrackColor != null);
assert(sliderTheme.thumbShape != null);
assert(sliderTheme.trackHeight != null && sliderTheme.trackHeight! > 0);
final Rect trackRect = getPreferredRect(
parentBox: parentBox,
offset: offset,
sliderTheme: sliderTheme,
isEnabled: isEnabled,
isDiscrete: isDiscrete,
);
final activeGradientRect = Rect.fromLTRB(
trackRect.left,
(textDirection == TextDirection.ltr)
? trackRect.top - (additionalActiveTrackHeight / 2)
: trackRect.top,
thumbCenter.dx,
(textDirection == TextDirection.ltr)
? trackRect.bottom + (additionalActiveTrackHeight / 2)
: trackRect.bottom,
);
// Assign the track segment paints, which are leading: active and
// trailing: inactive.
final ColorTween activeTrackColorTween = ColorTween(
begin: sliderTheme.disabledActiveTrackColor,
end: sliderTheme.activeTrackColor);
final ColorTween inactiveTrackColorTween = darkenInactive
? ColorTween(
begin: sliderTheme.disabledInactiveTrackColor,
end: sliderTheme.inactiveTrackColor
)
: activeTrackColorTween;
final Paint activePaint = Paint()
..shader = gradient.createShader(activeGradientRect)
..color = activeTrackColorTween.evaluate(enableAnimation)!;
final Paint inactivePaint = Paint()
..color = inactiveTrackColorTween.evaluate(enableAnimation)!;
final Paint leftTrackPaint;
final Paint rightTrackPaint;
switch (textDirection) {
case TextDirection.ltr:
leftTrackPaint = activePaint;
rightTrackPaint = inactivePaint;
break;
case TextDirection.rtl:
leftTrackPaint = inactivePaint;
rightTrackPaint = activePaint;
break;
}
final Radius trackRadius = Radius.circular(trackRect.height / 2);
final Radius activeTrackRadius = Radius.circular(trackRect.height / 2 + 1);
context.canvas.drawRRect(
RRect.fromLTRBAndCorners(
trackRect.left,
(textDirection == TextDirection.ltr)
? trackRect.top - (additionalActiveTrackHeight / 2)
: trackRect.top,
thumbCenter.dx,
(textDirection == TextDirection.ltr)
? trackRect.bottom + (additionalActiveTrackHeight / 2)
: trackRect.bottom,
topLeft: (textDirection == TextDirection.ltr)
? activeTrackRadius
: trackRadius,
bottomLeft: (textDirection == TextDirection.ltr)
? activeTrackRadius
: trackRadius,
),
leftTrackPaint,
);
context.canvas.drawRRect(
RRect.fromLTRBAndCorners(
thumbCenter.dx,
(textDirection == TextDirection.rtl)
? trackRect.top - (additionalActiveTrackHeight / 2)
: trackRect.top,
trackRect.right,
(textDirection == TextDirection.rtl)
? trackRect.bottom + (additionalActiveTrackHeight / 2)
: trackRect.bottom,
topRight: (textDirection == TextDirection.rtl)
? activeTrackRadius
: trackRadius,
bottomRight: (textDirection == TextDirection.rtl)
? activeTrackRadius
: trackRadius,
),
rightTrackPaint,
);
}
}
(Github要点)
你可以试试这个;
Widget get gradientContainer => Container(
width: double.infinity,
height: height,
decoration: BoxDecoration(
gradient: gradient
),
);
Widget get slider =>SliderTheme(
data: SliderThemeData(
trackShape: CustomTrackShape(),
activeTrackColor: Colors.transparent,
inactiveTrackColor: Colors.red,
thumbColor: Colors.white,
overlayColor: Colors.transparent
),
child: Slider(
value: value,
max: max,
min: min,
onChanged: (double newValue){
setState(() {
value=newValue;
});
}
)
);
为了在滑块上放置轨道填充,我们的自定义轨道形状类也在这里;
class CustomTrackShape extends RoundedRectSliderTrackShape {
Rect getPreferredRect({
@required RenderBox parentBox,
Offset offset = Offset.zero,
@required SliderThemeData sliderTheme,
bool isEnabled = false,
bool isDiscrete = false,
}) {
final double trackHeight = sliderTheme.trackHeight;
final double trackLeft = offset.dx;
final double trackTop = offset.dy + (parentBox.size.height - trackHeight) / 2;
final double trackWidth = parentBox.size.width;
return Rect.fromLTWH(trackLeft, trackTop, trackWidth, trackHeight);
}
}
我们终于可以合并它们了;
Widget get gradientSlider=>Padding(
child: SizedBox(
child: Stack(
children: [
gradientContainer,
slider,
],
alignment: Alignment.center,
),
),
padding: padding
);
最后你只需要填充填充,宽度,高度,渐变按钮容器高度属性,就这样。
使用这个库。用它来实现真的很容易,
https://pub.dev/packages/flutter_xlider
FlutterSlider(
values: [40],
max: 100,
min: 0,
trackBar: FlutterSliderTrackBar(
activeTrackBar: BoxDecoration(
gradient: AppColors.sliderGradient,
borderRadius: BorderRadius.circular(5)
),
activeTrackBarHeight: 6,
),
onDragging: (handlerIndex, lowerValue, upperValue) {
},
);
**更新
似乎 pub 版本尚未更新为空安全。但 master 分支有它。空安全版本使用如下
flutter_xlider:
git:
url: https://github.com/Ali-Azmoud/flutter_xlider.git
ref: master