private void toggleLines() {
            hasLines = !hasLines;

            generateData();
        }
Adds lines to data, after that data should be set again with
{@link LineChartView#setLineChartData(LineChartData)}. Last 4th line has non-monotonically x values.
hellocharts-samples/src/lecho/lib/hellocharts/samples/LineChartActivity.java