onPanStart method
Implementation
@protected
void onPanStart() {
// When panning starts, measure tick provider should not update ticks.
// This is still needed because axis internally updates the tick location
// after the tick provider generates the ticks. If we do not tell the axis
// not to update the location of the measure axes, we get a jittery effect
// as the measure axes location changes ever so slightly during pan/zoom.
_chart!.getMeasureAxis().lockAxis = true;
_chart!.getMeasureAxis(axisId: Axis.secondaryMeasureAxisId).lockAxis = true;
}