Touching a plotSymbol in CorePlot

Question

I'm trying to run some code when the user clicks (or touches) a plotSymbol on mye graph created with Core Plot.

This does not work with scatterPlot:

-(void)scatterPlot:(CPScatterPlot *)plot plotSymbolWasSelectedAtRecordIndex:    (NSUInteger)index
{
    NSLog(@"plotSymbolWasSelectedAtRecordIndex %d", index); 
}

But this works well when I use the barPlot:

-(void)barPlot:(CPBarPlot *)plot barWasSelectedAtRecordIndex:(NSUInteger)index
{
    NSLog(@"barWasSelectedAtRecordIndex %d", index);
}

What's missing from my attempt to capture when the user clicks or touches on my scatterPlot?

Answer 1

You need to set the plotSymbolMarginForHitDetection on your scatter plot. You should set it to match the size of your plot symbols or slightly larger if you need a bigger target to click.

Answer 2

Also, don't forget to set the CPScatterPlot's delegate to point to your object, or it won't get called.

Answer 3

If you're setting up your stuff at init time in a subclass of CPTGraphHostingView (say in initWithCoder coming from a xib), your hostedGraph property might get clobbered by Core Plot (at least as of 1.3), and so the tap handling will short-circuit.

https://code.google.com/p/core-plot/issues/detail?id=555

Needless to say this happened to me :-) My workaround is to set the hostedGraph in my numberOfRecordsForPlot if it's not set already.