HighCharts折线图-如何防止取消最后一个图例项的选择？

Question

Is there a way to prevent the hiding of the last legend item that's being deselected in a line chart?

I've achieved it on a column/pie charts using the legendItemClick event:

legendItemClick: function (e) {
    var self = this;
    var hiddenSeries = function () {
        var counter = 0;
        $.each(self.series.points, function (i, v) {
            if (!v.visible) {
                counter++;
            }
        });
        return counter;
    }

    if (self.series.points.length - 1 == hiddenSeries() && self.visible) {
        return false;
    } else {
        return true;
    }
}

and it works pretty well as you can see on the following fiddle , however, it doesn't work with line charts since the 'this' object doesn't contain the 'series.points' property.

Answer 1

You can refer to the chart variable to get at the series info. I did it like this:

           legendItemClick: function (e) {
                var visibleSeries = function () {
                    var counter = 0;
                    $.each(chart.series, function (i, v) {
                        if (v.visible) {
                            counter++;
                        }
                    });
                    return counter;
                }
                if (visibleSeries() <= 1 && this.visible) {
                    return false;
                } else {
                    return true;
                }
            }

http://jsfiddle.net/4tpsG/