Axis in Flutter Radial Gauge (SfRadialGauge)
18 Oct 202124 minutes to read
The radial axis is a circular arc in which a set of values are displayed along a linear or custom scale based on the design requirements. Axis elements such as labels, ticks, and axis line can be easily customized with built-in properties.
Axis Customization
Axis minimum and maximum
The minimum and maximum properties of an axis can be used to customize the axis range.The default value of minimum is 0, and the default value of maximum is 100.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(minimum: -60, maximum: 60
)
]
),
),
);
}
Angle Customization
The start and end angles of radial axis can be customized using the startAngle and endAngle properties.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(startAngle: 180, endAngle: 90,
)
]
),
),
);
}
Radius customization
The radius of the radial axis can be customized using the radiusFactor property. The default value of the radiusFactor is 0.95. The value of radiusFactor ranges from 0 to 1. For example, When the radiusFactor value is 1, the full radius will be considered for rendering the axis, and when the radiusFactor value is 0.5, then half of the radius value will be considered for rendering the circle.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(),
RadialAxis(radiusFactor: 0.5)]
),
),
);
}
Axis position customization
The position of the radial axis can be customized using the centerX and centerY values. The default value of centerX and centerY properties is 0.5. Therefore, the axis will be positioned in the center of provided size of gauge.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(startAngle: 270, endAngle: 270, interval: 10),
RadialAxis( centerY: 0.55, centerX: 0.35,
radiusFactor: 0.3, startAngle: 270,
endAngle: 270, interval: 20
)
]
),
),
);
}
Positioning axis based on its angle
The canScaleToFit property of radial axis allows to position the axis and its features based on the provided start and end angle. By default, the canScaleToFit is false, therefore the axis will be positioned based on the centerX and centerY value.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes: <RadialAxis>[RadialAxis( startAngle: 180, endAngle: 0,
interval: 10,
canScaleToFit: true)]),
),
);
}
Axis label rotation
The axis label can be rotated based on its current angle using the canRotateLabels property of axis. The default value of canRotateLabels is false.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(canRotateLabels: true)]
),
),
);
}
Edge label customization
The visibility of the first and last labels of an axis can be customized using the showFirstLabel and showLastLabel properties.
-
showFirstLabel– Enables or disables the first label of the axis. -
showLastLabel– Enables or disables the last label of the axis.
The default value of both the showFirstLabel and the showLastLabel properties is true.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis( interval: 1, showFirstLabel: false,
startAngle: 270, endAngle: 270, minimum: 0, maximum: 12),
]
),
),
);
}
Axis direction customization
The direction of radial axis can be customized by its isInversed property.
When the isInversed property is true, the axis can be placed in counter-clockwise direction. When the isInversed property is set to false, the axis will be positioned in clockwise direction.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis( isInversed: true)]
),
),
);
}
Maximum number of labels per 100 logical pixels
By default, a maximum of three labels are displayed for each 100 logical pixels in an axis. The maximum number of labels that should present within 100 logical pixels length can be customized using the maximumLabels property of the axis. This property is applicable only for automatic range calculation and will not work if you set value for interval property of an axis.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis( maximumLabels: 5)]
),
),
);
}
Interval
The interval between labels can be customized using the interval property of axis.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(interval: 20)]
),
),
);
}
Axis line customization
The radial axis line can be customized using the axisLineStyle property. The following properties can be customized using axisLineStyle.
-
thickness– Customizes the thickness of axis line. -
thicknessUnit– Allows to specify the thickness of the axis either in logical pixel or factor. Its default value is logicalPixel. -
color– Customizes the color of the axis line. -
cornerStyle– Allows to customize the corner of the axis line. -
dashArray– Allows to customize the axis line as dashed circular arc. -
gradient- Allows to apply the gradient for axis line.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(
axisLineStyle: AxisLineStyle(thickness: 0.1,
thicknessUnit: GaugeSizeUnit.factor, color: Colors.deepPurple,)),
]
),
),
);
}
Rounded Corners
The cornerStyle property of axisLineStyle specifies the corner type for axis line. The corners can be customized using the bothFlat, bothCurve, startCurve, and endCurve options. The default value of this property is bothFlat.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(axisLineStyle: AxisLineStyle(thickness: 15,
cornerStyle:CornerStyle.bothCurve)),
]
),
),
);
}
Dashed axis line
The dashArray property of axisLineStyle allows to render the dashed axis line.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(
axisLineStyle: AxisLineStyle( dashArray: <double>[5,5])),
]
),
),
);
}
Gradient support
The gradient property of axisLineStyle allows to specify the smooth color transition to the axis line by specifying the different colors based on provided factor value.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(
axisLineStyle: AxisLineStyle(thickness: 0.1,
thicknessUnit: GaugeSizeUnit.factor,
gradient: const SweepGradient(
colors: <Color>[Color(0xFFFF7676), Color(0xFFF54EA2)],
stops: <double>[0.25, 0.75]
),
)
),
]
),
),
);
}
Axis line visibility
The visibility of the axis line can be customized using the showAxisLine property of axis. By default, this property is set to true.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(showAxisLine: false)]
),
),
);
}
Background color support
Radial gauge allows customizing its background color using backgroundColor property.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
backgroundColor: Colors.lightBlue,
axes: <RadialAxis>[RadialAxis()],
)),
);
}
Background image support
Radial axis allows to add an image frame as its background using backgroundImage property.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Padding(
padding: EdgeInsets.fromLTRB(10, 0, 10, 0),
child: SfRadialGauge(
axes: <RadialAxis>[
RadialAxis(showAxisLine: false,
radiusFactor: 1,
showLastLabel: false,
canRotateLabels: true,
tickOffset: 0.32,
offsetUnit: GaugeSizeUnit.factor,
onLabelCreated: axisLabelCreated,
startAngle: 270,
endAngle: 270,
labelOffset: 0.05,
maximum: 360,
minimum: 0,
interval: 30,
minorTicksPerInterval: 4,
axisLabelStyle: GaugeTextStyle(color: const Color(0xFF949494)),
minorTickStyle: MinorTickStyle(color: const Color(0xFF616161),
thickness: 1.6,
length: 0.058,
lengthUnit: GaugeSizeUnit.factor),
majorTickStyle: MajorTickStyle(color: const Color(0xFF949494),
thickness: 2.3,
length: 0.087,
lengthUnit: GaugeSizeUnit.factor),
backgroundImage: const AssetImage(
'images/dark_theme_gauge.png'),
pointers: <GaugePointer>[
MarkerPointer(value: 90,
color: const Color(0xFFDF5F2D),
enableAnimation: true,
animationDuration: 1200,
markerOffset: 0.71,
offsetUnit: GaugeSizeUnit.factor,
markerType: MarkerType.triangle,
markerHeight: 10,
markerWidth: 15)
],
annotations: <GaugeAnnotation>[
GaugeAnnotation(angle: 270,
positionFactor: 0.025,
widget: Text('90',
style: TextStyle(
color: const Color(0xFFDF5F2D),
fontWeight: FontWeight.bold,
fontSize: 22
)
)
)
]
)
],
),
)
),
);
}
void axisLabelCreated(AxisLabelCreatedArgs args) {
if (args.text == '90') {
args.text = 'E';
args.labelStyle = GaugeTextStyle(
color: const Color(0xFFDF5F2D));
}else{
if (args.text == '0') {
args.text = 'N';
}else if (args.text == '180') {
args.text = 'S';
} else if (args.text == '270') {
args.text = 'W';
}
args.labelStyle = GaugeTextStyle(
color: const Color(0xFFFFFFFF),
);
}
}
Label style customization
The axis labels can be customized using the axisLabelStyle property of axis. The following properties can be customized using the axisLabelStyle.
-
color– Allows to customize the color of the labels. -
fontFamily– Allows to specify the font family for labels. -
fontStyle– Allows to specify the font style for labels. -
fontWeight– Allows to specify the font weight for labels. -
fontSize– Allows to specify the font size for labels.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(axisLabelStyle: GaugeTextStyle(
color: Colors.red, fontSize: 15,
fontStyle:FontStyle.italic,
fontWeight: FontWeight.bold, fontFamily: 'Times') ),
]
),
),
);
}
Formatting axis label
The following property of the axis allows to customize the axis label text.
-
labelFormat- Allows to add prefix or suffix with the axis labels.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(labelFormat: '{value}m' ),]
),
),
);
}
-
numberFormat- Allows to customize the axis label with theglobalized label format.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(
numberFormat: NumberFormat.compactSimpleCurrency()),
]
),
),
);
}
Label visibility
The showLabels property of axis allows to enable or disable the visibility of labels. The default value of the property is true.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(showLabels: false ),]
),
),
);
}
Tick customization
The major and minor tick lines of an axis can be customized using the majorTickStyle and minorTickStyle properties respectively. The following properties can be customized for both the major and the minor ticks:
-
color– Allows to customize the tick color. -
thickness– Allows to customize the thickness of ticks. -
length– Specifics the length of ticks. -
lengthUnit– Allows to specify the tick length either in logical pixels or factor. -
dashArray– Specify the dash array to draw the dashed tick line.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(majorTickStyle: MajorTickStyle(length: 0.1,
lengthUnit: GaugeSizeUnit.factor, thickness: 1.5, color: Colors.black),
minorTickStyle: MinorTickStyle(length: 0.05,
lengthUnit: GaugeSizeUnit.factor, thickness: 1.5, color: Colors.black)
)]
),
),
);
}
Dashed tick lines
The dashArray property of both the majorTickStyle and minorTickStyle allows to draw the tick line as dashed line.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(
majorTickStyle: MajorTickStyle(length: 20, dashArray: <double>[5,2.5]),
minorTickStyle: MinorTickStyle(length: 15, dashArray: <double>[3,2.5])),
]
),
),
);
}
Minor tick interval
The major ticks are generated based on the interval property. Like major ticks, the minor ticks are calculated using the minorTicksPerInterval property of axis. By default, the value of this property is 1.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(minorTicksPerInterval: 4
),
]
),
),
);
}
Tick line visibility
The showTicks property of the axis is used to enable or disable the visibility of both the major and the minor ticks of axis. The default value of this property is true.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(showTicks: false)]
),
),
);
}
Label and tick Placement
The radial axis allows to position the labels and ticks either inside or outside the axis line using the labelsPosition and ticksPosition properties. By default, both labels and ticks are positioned inside the axis line.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(
labelsPosition: ElementsPosition.outside,
ticksPosition: ElementsPosition.outside)]
),
),
);
}
Tick position customization
The ticks can be moved near or far to the axis line using the tickOffset property. The offsetUnit property of axis allows to specify the tick offset either in factor or logical pixels, and the default value of offsetUnit is logicalPixel.
The default value of tick offset is 0. While setting offset for the ticks, the axis labels are also moved along with the ticks.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(
tickOffset: 20)]
),
),
);
}
The following code example shows how to add tick offset with the offsetUnit property of axis.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(tickOffset: 0.2,
labelOffset: 0.2, offsetUnit: GaugeSizeUnit.factor
),
]
),
),
);
}
Label position customization
The labelOffset property allows to adjust the distance between the tick end and the labels. The offsetUnit property of axis allows to specify the label offset either in factor or logical pixels. By default, the value of the label offset is 15.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(
labelOffset: 0.3, offsetUnit: GaugeSizeUnit.factor
),
]
),
),
);
}
The offsetUnit property of axis is common for both the tickOffset and labelOffset.
NOTE
GaugeSizeUnitallows to specify the value either in logical pixels or in factor. GaugeSizeUnit.factor ranges from 0 to 1. For example, when setting factor as 0.5, the half of axis radius value will be considered.
Multiple axis
The Radial Gauge allows you to add n number of radial axis in its axes collection. You can also customize individual axis added in the axes collection.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes: <RadialAxis>[ RadialAxis(minimum: 0 , maximum: 100, interval: 10,
ticksPosition: ElementsPosition.outside,
labelsPosition: ElementsPosition.outside,
minorTicksPerInterval: 5,
radiusFactor: 0.9, labelOffset: 15,
minorTickStyle: MinorTickStyle(thickness: 1.5,
color: Color.fromARGB(255, 143, 20, 2),
length: 0.07, lengthUnit: GaugeSizeUnit.factor),
majorTickStyle: MinorTickStyle(thickness: 1.5,
color: Color.fromARGB(255, 143, 20, 2),
length: 0.15, lengthUnit: GaugeSizeUnit.factor,),
axisLineStyle: AxisLineStyle( thickness: 3,
color: Color.fromARGB(255, 143, 20, 2), ),
axisLabelStyle: GaugeTextStyle(fontSize: 12,
color:Color.fromARGB(255, 143, 20, 2),),),
RadialAxis(minimum: 0 , maximum: 60, interval: 10,
radiusFactor: 0.6, labelOffset: 15, isInversed: true,
minorTicksPerInterval: 5,
minorTickStyle: MinorTickStyle(color: Colors.black, thickness: 1.5,
lengthUnit: GaugeSizeUnit.factor, length: 0.07),
majorTickStyle: MajorTickStyle(color: Colors.black, thickness: 1.5,
lengthUnit: GaugeSizeUnit.factor, length: 0.15),
axisLineStyle: AxisLineStyle(color: Colors.black, thickness: 3, ),
axisLabelStyle: GaugeTextStyle(color: Colors.black, fontSize: 12)),
],
)
),
);
}
Events
onLabelCreated
The onLabelCreated event is called when an axis label is created. The following properties can be customized for the corresponding axis label when this event args:
-
text– Allows to customize the text property of label. -
labelStyle– Customizes the label color, font style, font family, and font weight. -
canRotate– Specifies whether to rotate the label based on its current angle.
NOTE
If both
axisLabelStyleproperty of radial axis andlabelStyleproperty of theonLabelCreatedevent args are set, the values of thelabelStyleproperty of the event args will take precedence.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(
onLabelCreated:axisLabelCreated,),
]
),
),
);
}
void axisLabelCreated(AxisLabelCreatedArgs args){
if(args.text == '100'){
args.labelStyle = GaugeTextStyle(color: Colors.red,fontStyle: FontStyle.italic,
fontFamily: 'Times', fontWeight: FontWeight.bold, fontSize: 15);
args.canRotate = true;
args.text = '100 %';
}
}
onAxisTapped
The onAxisTapped event is called when an axis is tapped. The corresponding axis value at the tapped position will be got from the event.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(
axes:<RadialAxis>[RadialAxis(
onAxisTapped: axisTapped),
]
),
),
);
}
void axisTapped(double _tappedValue){
}Custom scale
Radial gauge allows you to display a set of values along with a custom scale based on your business logic using the onCreateAxisRenderer event of the axis. The onCreateAxisRenderer event allows returning the custom renderer for the axis. In that, we can override methods of RadialAxisRenderer to create the custom axis.
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SfRadialGauge(axes: <RadialAxis>[
RadialAxis(
minimum: 0,
maximum: 150,
onCreateAxisRenderer: () {
final CustomAxisRenderer renderer = CustomAxisRenderer();
return renderer;
},
)
]),
),
);
}
class _CustomAxisRenderer extends RadialAxisRenderer {
_CustomAxisRenderer() : super();
/// Generated the 9 non-linear interval labels from 0 to 150
/// instead of actual generated labels.
@override
List<CircularAxisLabel> generateVisibleLabels() {
final List<CircularAxisLabel> _visibleLabels = <CircularAxisLabel>[];
for (num i = 0; i < 9; i++) {
final double _value = _calculateLabelValue(i);
final CircularAxisLabel label = CircularAxisLabel(
this.axis.axisLabelStyle, _value.toInt().toString(), i, false);
label.value = _value;
_visibleLabels.add(label);
}
return _visibleLabels;
}
/// Returns the factor(0 to 1) from value to place the labels in an axis.
@override
double valueToFactor(double value) {
if (value >= 0 && value <= 2) {
return (value * 0.125) / 2;
} else if (value > 2 && value <= 5) {
return (((value - 2) * 0.125) / (5 - 2)) + (1 * 0.125);
} else if (value > 5 && value <= 10) {
return (((value - 5) * 0.125) / (10 - 5)) + (2 * 0.125);
} else if (value > 10 && value <= 20) {
return (((value - 10) * 0.125) / (20 - 10)) + (3 * 0.125);
} else if (value > 20 && value <= 30) {
return (((value - 20) * 0.125) / (30 - 20)) + (4 * 0.125);
} else if (value > 30 && value <= 50) {
return (((value - 30) * 0.125) / (50 - 30)) + (5 * 0.125);
} else if (value > 50 && value <= 100) {
return (((value - 50) * 0.125) / (100 - 50)) + (6 * 0.125);
} else if (value > 100 && value <= 150) {
return (((value - 100) * 0.125) / (150 - 100)) + (7 * 0.125);
} else {
return 1;
}
}
/// To return the label value based on interval
double _calculateLabelValue(num value) {
if (value == 0) {
return 0;
} else if (value == 1) {
return 2;
} else if (value == 2) {
return 5;
} else if (value == 3) {
return 10;
} else if (value == 4) {
return 20;
} else if (value == 5) {
return 30;
} else if (value == 6) {
return 50;
} else if (value == 7) {
return 100;
} else {
return 150;
}
}
}