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A library for customizable gauges (radial gauges only for now).

gauges #

Note: This project serves as a training exercise for myself in order to better understand the inner workings of Flutter and learn how to write custom Widgets, Elements and RenderObjects from scratch. As a result, the API might change heavily and I may not know about best practices or optimal solutions for many problems. So if you have any suggestions of improvement, please feel free to open an issue.

Getting started #

To use this plugin, add [flutter_gauges] as a dependency in your pubspec.yaml file.

Usage #

Radial gauge #

The basic widget for radial gauges is the RadialGauge. Multiple axes can be added. E. g. this is a gauge with three axes:

This is the basic structure of a RadialGauge. See the following sections for more info on each of them.

RadialGauge(
  axes: [
    RadialGaugeAxis(
        segments: [
            RadialGaugeSegment(),
            RadialGaugeSegment(),
            // ...
        ],
        pointers: [
            RadialNeedlePointer(),
            RadialNeedlePointer(),
            // ...
        ],
        ticks: [
            RadialTicks(
                children: [
                    RadialTick(),
                    RadialTick(),
                ],
            ),
            RadialTick(),
            // ...
    ),
    RadialGaugeAxis(
    ),
  ],
)

Axes

An axes has a few important properties:

  • min: The minimum value of this axes
  • max: The maximum value of this axes
  • minAngle: The angle in degrees min is mapped to
  • maxAngle: The angle in degrees max is mapped to
  • radius: The radius of the axes as a fraction of the RadialGauge's size
  • width: The width of the axes as a fraction of the RadialGauge's size
  • offset: The offset of the axes in respect to the middle of the RadialGauge
  • color: The color of the axes (gradients are also available, see examples)

For more, take a look at the examples.

RadialGauge(
  axes: [
    RadialGaugeAxis(
      minValue: -100,
      maxValue: 100,
      minAngle: -150,
      maxAngle: 150,
      radius: 0.6,
      width: 0.2,
    ),
  ],
)

Segments

Each axes can consist of multiple segments (it is, in fact, a segment itself). Each of the segments has a properties similiar to the RadialGaugeAxis. The segments are listed in the segments property of an axes:

RadialGauge(
  axes: [
    RadialGaugeAxis(
      color: Colors.transparent,
      // ...
      segments: [
        RadialGaugeSegment(
          minValue: 0, 
          maxValue: 20, 
          minAngle: -150, 
          maxAngle: -130,
          color: Colors.red,
        ),
        RadialGaugeSegment(
          minValue: 20, 
          maxValue: 40, 
          minAngle: -120, 
          maxAngle: -90,
          color: Colors.orange,
        ),
          // ...
      ],
    ),
  ],
)

Ticks

Each axes can have multiple ticks of type RadialTick. They are listed in the ticks property. There are multiple possibilities to create ticks.

  • Interval: Set the interval to the desired value. The ticks are displayed on every integer multiple of interval.
  • Ticks in between: Set ticksInBetween to the desired number of ticks in between the parent ticks or the axes limits.
  • Custom values: Set values to the desired values you want the ticks to appear at.
  • Custom builder: Set valuesBuilder and/or anglesBuilder to a custom function calculating the values and/or angles at which the ticks should be displayed.

Every RadialTick can have RadialTicks as children, which is especially useful when setting the ticksInBetween on a children tick.

RadialGaugeAxis(
  // ...
  color: Colors.transparent,
  ticks: [
    RadialTicks(
        interval: 20,
        alignment: RadialTickAxisAlignment.inside,
        color: Colors.blue,
        length: 0.2,
        children: [
          RadialTicks(
              ticksInBetween: 5,
              length: 0.1,
              color: Colors.grey[500]),
        ])
  ],
)

Pointer

Each axis can have multiple pointers. Currently, there is only one type of pointer available, the RadialNeedlePointer with the following properties:

  • value: The value the pointer is pointing to
  • ticknessStart: The thickness of the pointer at the start of the pointer (in the middle of the axis)
  • ticknessEnd: The thickness of the pointer at the end of the pointer
  • length: The length of the pointer in fractions of the axis.
  • knobRadiusAboslute: The radius of the pointer's knob in absolute pixels.
  • color/gradient: The color/gradient filling the pointer.

The following code results in the knob shown above. For more, take a look at the examples.

RadialGaugeAxis(
    pointers: [
        RadialNeedlePointer(
            value: _pointerValue,
            thicknessStart: 20,
            thicknessEnd: 0,
            length: 0.6,
            knobRadiusAbsolute: 10,
            gradient: LinearGradient(...),
        )
    ],
)

Linear gauge #

Not available yet

Maintainer #

Julian Aßmann

39
likes
120
pub points
89%
popularity

Publisher

verified publisherjulianassmann.de

A library for customizable gauges (radial gauges only for now).

Homepage
Repository (GitHub)
View/report issues

Documentation

API reference

License

MIT (LICENSE)

Dependencies

flutter

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