Vertical bar chart: capture of scrollView delegate callbacks and load additional data

[nspassov]

Hey guys,

I have a vertical bar chart. It has lots of data that doesn't fit the screen width so I have enabled scaling on the X axis. Is it possible to capture the scrollView offset when chart scaling is on as I would like to trigger a request for more data when the scrolling reaches the bounds of the chart?

[liuxuan30]

it's a good quesiton. When you reach the end, you will know it's the last xIndex, and then you can add more data entries by addEntry.
you can take a look at how panGestureRecognized, performPanChange are implemented. It should be helpful. It does have a delegate called chartTranslated(chartView: ChartViewBase, dX: CGFloat, dY: CGFloat) so you know the offset.

[nspassov]

The dX value that chartTranslated method gives is not the content offset like in a tableView, but something else. It is some kind of delta and this method also gets triggered when swiping that does not result in actual change of the position (swiping at the edge of the chart). This is what I am currently using but so far it doesn't quite do the job.

[liuxuan30]

yes, it's not about content offset. You have to do some math to know if it reaches the end. It seems like this part can be improved in the future.

[shardul89]

@liuxuan30 is there any specific methoid which gets called to load next set of chart data when chart reaches end of the scroll?

[liuxuan30]

I don't remember, but maybe you can bind some methods from ViewPortHandler to see if possible.
Maybe highestVisibleX could help as well.