If you followed the getting started article, you now know how to create a chart and add it to a NativeScript page. In this article, you will learn how to add a trackball that can be used to display additional information about a highlighted point. For example, in a Financial chart the
Trackball can display the Open, High, Low and Close value of a stock for a single day. The Trackball is displayed when the user holds a finger on the plot area of the chart and drags it through the set of data points a given series represents.
RadCartesianChart supports displaying a trackball via its
Example 1: A Cartesian Chart with a Trackball
<RadCartesianChart row="1" tkExampleTitle tkToggleNavButton> <DateTimeCategoricalAxis tkCartesianHorizontalAxis dateFormat="yyyy-MM-dd" verticalLocation="Bottom"></DateTimeCategoricalAxis> <LinearAxis tkCartesianVerticalAxis></LinearAxis> <Trackball tkCartesianTrackball></Trackball> <CandlestickSeries tkCartesianSeries categoryProperty="Date" [items]="candleStickSourceItems" openPropertyName="Open" highPropertyName="High" lowPropertyName="Low" closePropertyName="Close"> </CandlestickSeries> </RadCartesianChart>
Depending on your current setup, the trackball will display information about the data points within the chart in a different manner. For example, in a
RangeBarSeries the trackball will display the range values alongside with the current category value. In a
CandlestickSeries the trackball will display the Open, High, Low and Close values alongside with the current category value. Here's an example:
Figure 1: Trackball shown in action on Android (left) and iOS (right)
By using the
showIntersectionPoints property you can determine whether information about all of the relevant data points will be shown in the trackball. This behavior is dependent on the
snapMode property setting.
You can customize the content within the trackball by using the
trackBallContentRequestedEvent event. This event is fired each time information about a given data point is needed for the trackball. The event exposes an instance of the
TrackballCustomContentData. This class extends the
ChartEventData class and adds two new properties:
seriesIndex- the index of the active series with which the user has started interacting
content- used to override the default data point content. By setting this property you can customize the content within the trackball for the provided data point. You can use the base event data properties to obtain the data point index and the business object for which the data point has been generated for
Want to see this scenario in action? Check our SDK Examples repository on GitHub. You will find this and many other practical examples with NativeScript UI.
Examples used in this article:
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