ZK Charts Essentials/Working with ZK Charts/Drag Points

You can enable draggable-points for one or all series, then users can drag to move a data point in a chart:

DraggablePointComposer.java

    private Charts chart;
...

        //enable drag and drop for a specific series
        chart.getSeries().getDragDrop().setDraggableY(true);
        //enable drag and drop for all series
        chart.getPlotOptions().getSeries().getDragDrop().setDraggableX(true);

Listening to dragstart, drag and drop events

applicable to version 10.3.3.0

With drag and drop enabled, it is possible to register a client-side javascript handler which will be invoked when the relevant action is performed:

• dragStart: when the user starts dragging
• drag: during drag, when the user moves the element
• drop: once the user releases the drag, and the element is dropped

In this client-side handler, we can use the zAu.send function to forward this event to the server.

Note: avoid sending the drag handler if not necessary, since this handler may fire a large number of requests while the user is dragging.

    @Wire
    private Charts chart; //use the chart component as anchor
    
    private void enableDraggablePoints() {
        //enable drag and drop for a specific series
        chart.getSeries().getDragDrop().setDraggableY(true);
        //create an object to hold the point value
        JSONObject pointValue = new JSONObject();
        //create an object to hold the point.events value
        JSONObject eventsValue = new JSONObject();
        //set the content of the point.events.drop callback
        eventsValue.put("drop", new JavaScriptValue("function(e){zAu.send(new zk.Event(zk.$('#"+chart.getUuid()+"'), 'onPointDrop', {pointData: e.newPoint, serieIndex: e.origin.points[e.newPointId].point.series.index, pointIndex:e.origin.points[e.newPointId].point.index}, {toServer:true}));}"));
		pointValue.put("events", eventsValue);
		chart.getPlotOptions().getSeries().addExtraAttr("point", pointValue);
    }

    @Listen("onPointDrop=#chart")
    public void handleDrop(Event event) {
    	Map data = (Map) event.getData();
    	Map pointData = (Map) data.get("pointData");
    	Double y = (Double) pointData.get("y");
    	int serieIndex = (int) data.get("serieIndex");
    	int pointIndex = (int) data.get("pointIndex");
    	Clients.log("new point data: " + y + " series (" +serieIndex+"), point (" +pointIndex+ ")");
    }

Here is a decompressed version of the handler script for clarification:

function(e){ // callback from dragStart, drag, or drop, e is the highcharts event containing the point data
	zAu.send( // send an event to the server
		new zk.Event( // create a new event with the following parameters
			zk.$('#"+chart.getUuid()+"'), // retrieve the charts component as the event target. The component is retrieved using the zk.$('#uuid') syntax.
			'onPointDrop', // create a custom event. This custom event name will be used when registering the event listener, either with addEventListener, or using @Listen
			{pointData: e.newPoint, serieIndex: e.origin.points[e.newPointId].point.series.index, pointIndex:e.origin.points[e.newPointId].point.index}, //retrieve point data and pass it with the event
			{toServer:true} //indicate that the event should be sent immediately, and not wait for piggybacking on the next request
		)
	);
}

Reference: Highcharts API Rerenence

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