ChartView for Xamarin.Android: Axes

RadCartesianChartView plots data points in a coordinate system defined by its two axes. Usually, one data point has category and value, which define its Cartesian coordinates. This means that your chart will need one axis that can visualize the category and another which can visualize the value. CartesianAxis is the base class for all axes that RadCartesianChartView can plot.

Category axes

The axes that can be used to visualize the category of a data point are:

• CategoricalAxis: The CategoricalAxis extends the CartesianAxis. It is the base axis that can be used to display category of any kind.
• DateTimeCategoricalAxis: The DateTimeCategoricalAxis extends the CategoricalAxis. It can be used if the category of the data points is of type Calendar.
• DateTimeContinuousAxis: The DateTimeContinuousAxis extends the CartesianAxis. It may be considered as a hybrid between a categorical and a numerical (linear) axis. DateTimeContinuousAxis works with categorical data but instead of categories, the axis builds time slots depending on its Minimum, Maximum and MajorStep values.

Value axes

The axes that can be used to visualize the value of a data point extend the NumericalAxis class. They are:

• LinearAxis: The LinearAxis extends the NumericalAxis class and plots the associated data points using each point's actual value, provided for the axis.
• LogarithmicAxis: The LogarithmicAxis is used to display values that cover several orders of magnitude in a more manageable way. This is a special numerical axis that transforms the actual values of the data points using logarithm function with a specific base.

Features

Each axis provides several important properties you can use to customize the axis' appearance. Here is a list of all properties that can be set on an Axis object:

• Related to axis ticks: MajorTickOffset (Sets the major value step between two ticks. By default the axis itself will calculate the

  • major step, depending on the plotted data points), TickThickness, TickColor

• Related to axis labels:

ShowLabels, LabelFont, LabelMargin, LabelTextColor, LabelFontStyle, LabelSize, , LabelRotationAngle, LastLabelVisibility, LabelFormat, LabelOffset, , LabelFitMode, LabelLayoutMode, LabelInterval, LabelRenderer LabelValueToStringConverter

Below is a description with examples of several properties which accept complex objects instead of simple values.

LabelValueToStringConverter

This is an interface that can be used to convert the actual label to value to an arbitrary string before rendering.

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LinearAxis verticalAxis = new LinearAxis();
verticalAxis.LabelValueToStringConverter = new LabelValueConverter();

private class LabelValueConverter : Java.Lang.Object, IFunction
{
    public Java.Lang.Object Apply(Java.Lang.Object argument)
    {
        double labelValue = (argument.JavaCast<MajorTickModel>()).Value();
        String format = "Value is: {0}";
        return String.Format(format, labelValue);
    }
}

LabelRenderer

An interface that allows developers to swap the label rendering with their own implementation.

    public class MyLabelRenderer : CartesianAxisLabelRenderer
    {
        public MyLabelRenderer(CartesianAxis axis):base(axis)
        {
        }

        protected override void RenderLabelNoFitMode(Android.Graphics.Canvas canvas,
            RadRect p1, string p2, AxisLabelModel p3)
        {
            // Draw something only when label fit mode is None
            Paint pink = new Paint();
            pink.Color = Color.ParseColor("#ff69b4");
            canvas.DrawRect(new RectF((float)p1.GetX(), (float)p1.GetY(), (float)p1.Right, (float)p1.Bottom), pink);
            base.RenderLabelNoFitMode(canvas, p1, p2, p3);
        }

        protected override void RenderLabelMultiLine(Canvas canvas, RadRect p1, string p2, AxisLabelModel p3)
        {
            // Draw something only when label fit mode is Multiline
            Paint khaki = new Paint();
            khaki.Color = Color.ParseColor("#f0e68c");
            canvas.DrawRect(new RectF((float)p1.GetX(), (float)p1.GetY(), (float)p1.Right, (float)p1.Bottom), khaki);
            base.RenderLabelMultiLine(canvas, p1, p2, p3);
        }

        protected override void RenderLabelRotate(Canvas canvas, RadRect p1, string p2, AxisLabelModel p3)
        {
            // Draw something only when label fit mode is ROTATE
            Paint moccasin = new Paint();
            moccasin.Color = Color.ParseColor("#ffe4b5");
            canvas.DrawRect(new RectF((float)p1.GetX(), (float)p1.GetY(), (float)p1.Right, (float)p1.Bottom), moccasin);
            base.RenderLabelRotate(canvas, p1, p2, p3);
        }

        public override void RenderLabel(Canvas p0, ChartNode p1)
        {
            // Always draw something before the given label is drawn.
            base.RenderLabel(p0, p1);
        }

        public override Com.Telerik.Android.Common.Math.RadSize MeasureLabel(AxisLabelModel p0, Java.Lang.Object p1)
        {
            // Plug some logic when the label is being measured.
            return base.MeasureLabel(p0, p1);
        }
    }

Finally, developers can use this custom label renderer by calling axis.setLabelRenderer(new MyLabelRenderer(axis)) or axis.LabelRenderer = new MyLabelRenderer(axis); for Xamarin.