Access to Underlying Widgets

• Aug 03, 2020
• 3 minutes to read

The Web Dashboard control uses DevExtreme widgets to visualize dashboard items’ data. You can access these widgets and customize their settings to add specific capabilities.

The DashboardControl exposes the following members that allow you to access these widgets and customize their settings:

• The ViewerApiExtensionOptions.onItemWidgetCreated property raises the ItemWidgetCreated event once for each widget when the dashboard is loaded to client. Handle this event to subscribe to events of the underlying widget.

• ViewerApiExtensionOptions.onItemWidgetUpdating and ViewerApiExtensionOptions.onItemWidgetUpdated properties raises the corresponding ItemWidgetUpdating and ItemWidgetUpdated events. Raise these events when the widget needs to be updated. For instance, this can be related to applying master filtering or changing parameter values.

  Use the ViewerApiExtensionOptions.onItemWidgetUpdating property to handle the ItemWidgetUpdating event to unsubscribe from the client widget’s events. The ViewerApiExtensionOptions.onItemWidgetUpdated property is used to customize widgets according your requirements. This allows you to prevent the DashboardControl from rewriting of customized options.

The ItemWidgetEventArgs.itemName property returns the component name of the dashboard item whose widget can be customized. Use the ItemWidgetEventArgs.getWidget property to access the corresponding underlying widget.

The following table lists dashboard items whose underlying widgets can be accessed when you handle the ItemWidget… events:

Dashboard Item	Underlying Widget(s)
GridItem	dxDataGrid
ChartItem ScatterChartItem	dxChart
PieItem	an array of dxPieChart widgets
GaugeItem	an array of dxCircularGauge or dxLinearGauge widgets
MapItem	dxVectorMap
PivotItem	dxPivotGrid
ComboBoxItem	dxSelectBox or dxTagBox
ListBoxItem	dxList
TreeViewItem	dxTreeList dxTreeView (for v17.1 and earlier)
TreemapItem	dxTreeMap
RangeFilterItem	dxRangeSelector
CardItem	CardWidget
DateFilterItem	DateFilterWidget
TextBoxItem	n/a[1]
ImageItem	n/a[1]
CustomItem	n/a[2]

Limitations

Do not change the following settings to avoid possible issues:

• data binding settings;
• basic data presentation settings (for instance, a set of grid columns or chart series).

Note that changes made with the ItemWidget… events do not change the dashboard/dashboard items’ appearance in exported documents.

Example

The following code snippets show how to customize client widgets used to visualize data within dashboard items at runtime on the client side.

The changed options are listed below:

• The hovered grid row is highlighted in the underlying dxDataGrid in the ViewerApiExtensionOptions.onItemWidgetCreated event handler.
• A standard tooltip that is invoked over a chart series point is disabled. You need to click the required label on the argument axis to invoke a tooltip. The argumentAxisClick event is used to change the behavior. Subscription and unsubscription to/from the argumentAxisClick event are performed in the ViewerApiExtensionOptions.onItemWidgetUpdated and ViewerApiExtensionOptions.onItemWidgetUpdating event handlers, respectively.
• A pie legend is shown for the underlying dxPieChart.

dashboard.component.ts

// ...
var dashboardControl = new DashboardControl(this.element.nativeElement.querySelector(".dashboard-container"),  {  
    endpoint: "https://demos.devexpress.com/services/dashboard/api",
    workingMode: "Designer",
    extensions: {
        "viewer-api": {
            onItemWidgetUpdated: "function(s, e) { customizeWidgets(e); }",
            onItemWidgetCreated: "function(s, e) { customizeWidgets(e); }",
            onItemWidgetUpdating: "function(s, e) { unsubscribeFromEvents(e); }"
        }
    }
});

widgets.customization.js

function customizeWidgets(args) {
    if (args.ItemName == "gridDashboardItem1") {
        var grid = args.GetWidget();
        grid.option({
            hoverStateEnabled: true
        });
    }
    if (args.ItemName == "chartDashboardItem1") {
        var chart = args.GetWidget();
        chart.option({
            tooltip: {
                enabled: false
            },
            onArgumentAxisClick: function (info) {
                info.component.getAllSeries()[0].getPointsByArg(info.argument)[0].showTooltip()
            }
        });
    }
    if (args.ItemName == "pieDashboardItem1") {
        var pie = args.GetWidget()[0];
        pie.option({
            legend: {
                visible: true,
                border: {
                    visible: true
                }
            }
        });
    }
}

function unsubscribeFromEvents(args) {
    if (args.ItemName == "chartDashboardItem1") {
        var chart = args.GetWidget();
        chart.option({
            onArgumentAxisClick: undefined
        });
    }
}

Footnotes

1. The content of the TextBoxItem and the ImageItem is an HTML element wrapped in a jQuery object.

2. The CustomItem is a custom widget. You can customize it directly.