1) I have an Androidplot XYPlot and some values are 0 to represent "no data" on that point. Can I hide these points with value "0" from the plot?
2) If I can't hide them, can I make the graph lines going from the previous point, to the 0 value point and to the next point, another color (like red) to show that this is a point "with no data"?
XYPlot's underlying model is XYSeries which uses Numbers to represent points. If you're implementing your own XYSeries then just return null from getX(i) / getY(i) where i is the index of any "no data" element.
If you're using SimpleXYSeries, then just pass null into the constructor, model or setX/Y method you're using to populate it.
When the plot is drawn, you should see your line(s) broken up where nulls are encountered.