ChartView for Xamarin.Android: Legend
In this article, you will learn to use the built-in legend in RadChartView for Android.
Overview
You can start from the BarSeries example and add a second instance of the BarSeries with stack combine mode. Then you need to set their legend title and create a new instance of RadLegendView. RadLegendView needs a legend provider which will provide the data. You can use RadCartesianChartView as a LegendProvider:
barSeries1.CombineMode = ChartSeriesCombineMode.Stack;
barSeries2.CombineMode = ChartSeriesCombineMode.Stack;
barSeries1.LegendTitle = "first";
barSeries2.LegendTitle = "second";
RadLegendView legendView = new RadLegendView (this);
legendView.LegendProvider = chartView;
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(460,100);
layoutParams.SetMargins(10,10,10,10);
legendView.LayoutParameters = layoutParams;
LinearLayout linearLayout = new LinearLayout(this);
linearLayout.Orientation = Android.Widget.Orientation.Vertical;
linearLayout.AddView(legendView);
linearLayout.AddView(chartView);
ViewGroup rootView = (ViewGroup)FindViewById(Resource.Id.container);
rootView.AddView(linearLayout);
Here's the result:
The legend for the pie chart is a little bit different. The pie series does not have a legend title because each point in the series means something different, the title is taken from the data points with a name binding. For example:
PieSeries series = new PieSeries();
// This assumes that the data models have a property with the signature public string Name { get; }.
series.NameBinding = new PropertyNameDataPointBinding("Name");
Orientation
The default behavior of the RadLegendView is to show the legend items vertically. However you can change the orientation of the items to horizontal with LegendOrientation property:
legendView.LegendOrientation = OrientationHelper.Horizontal;
The possible values for the orientation are:
- OrientationHelper.Horizontal
- OrientationHelper.Vertical
Scrolling
By default the scroll of the legend items is disabled. In order to enable the horizontal and vertical scroll you can use:
legendView.SetCanScrollHorizontally(true);
legendView.SetCanScrollVertically(true);
Selection
RadLegendView supports selection by setting the AllowSelection property to true.
legendView.AllowSelection = true;
The LegendItemSelected event can be used to determine the selected LegendItem.
private void LegendViewOnLegendItemSelected(object sender, LegendSelectionEventArgs e)
{
var title = (e.P0 as LegendItem)?.Title;
}