Core Plot show 'Loading' spinner

Question

I am using core plot (0.4) to render a graph and it is working fine. However (especially when on the iPad) the graph can take a while to render. I have added a UIActivityIndicatorView to the graph which shows up when the graphs starts to be drawn, but I can't find any event to hook that I can use to stop the spinner.

I have tried using the numberForPlot method and detecting when the last datapoint has been requested, but this is called multiple times for each line on the scatterGraph, so I can't easily use this. Is there any sort of graph rendered event that I can hook for this?

Answer 1

If you're doing [graph reloadData] to update the graph, can you just bracket that call with your indicator start/stop calls? I think that core-plot does everything in the main thread.

Answer 2

Core Plot uses Core Animation for all rendering. A single graph contains many CA layers that are rendered independently. -reloadData just tells the graph to update its data cache next time it draws and tells Core Animation that it needs to be redrawn. Similarly, just bracketing the data source calls only captures the data caching that happens before the render. You would miss the actual drawing time and would never know if Core Animation re-rendered the graph at another time, such as after a resize.

If you only care about the time to render the plot and not the other parts of the graph, one way to do this would be to subclass CPTScatterPlot and override the -renderAsVectorInContext: method. Bracket the calls to super with your activity indicator code.