问题
Using Core Plot's CPTScatterPlot, I've made a bubble chart that looks like the above.
I've implemented plotSymbolWasSelectedAtRecordIndex in my delegate so I can detect when the user touches one of the bubbles. Using this screenshot as an example, I want to be able to highlight the yellow bubble and bring it in front of the red one when the user touches it. In graphical terms, I want to set the Z order of the selected CPTPlotSymbol to be higher than the others. How can I accomplish that? I'm able to highlight the selected bubble by drawing it in a different color in my symbolForScatterPlot method, but I can't seem to find a way to make it draw in front of the overlapping symbol.
回答1:
Core Plot draws the data points in the order they appear in the datasource. You'll need to reorder the data so the top-most bubble is at the last index and call -reloadData on the plot to tell it to refresh its data. If you have the data points in an array, sort it by the desired z-index (back to front) and use the sorted array to feed the datasource.
来源：https://stackoverflow.com/questions/21635656/cptxyscatterplot-can-i-set-the-z-order-of-plot-symbols