Allow horizontal scrolling only in the core-plot barchart?

Question

Hi all,

I am using core-plot lib to draw bar charts in my app like this

My problem is that i want the enabling of grapgh movement only in horizontal direction so that I can see the records for a long period of time, But the problem is that i just wnt to keep the y axis fixed to its place,

How can i do this?

Waiting for help....

Answer 1

Only recently has rudimentary user interaction been enabled in Core Plot graphs. To enable scrolling in any direction, you can set the allowsUserInteraction property of the plot space to YES.

We currently have no means of locking that movement to one direction. The scrolling action takes place in the -pointingDeviceDraggedAtPoint: method on CPXYPlotSpace, so you could subclass CPXYPlotSpace, copy over its implementation of that method, and alter it to only allow movement in the X direction. Even better, we'd appreciate any contributions to extend the functionality of the CPXYPlotSpace to add support for unidirectional movement.

Answer 2

Limit scrolling by setting a delegate (i.e., CPPlotSpaceDelegate) on the plot space and implement the willChangePlotRangeTo method. You can do other cool things at the same time. Here's how I limit the display to quadrant one:

- (CPPlotRange *)plotSpace:(CPPlotSpace *)space
    willChangePlotRangeTo:(CPPlotRange *)newRange
            forCoordinate:(CPCoordinate)coordinate {

    // Display only Quadrant I: never let the location go negative.
    //
    if (newRange.doublePrecisionLocation < 0.0F) {
        newRange.location = CPDecimalFromFloat(0.0);
    }

    // Adjust axis to keep them in view at the left and bottom;
    // adjust scale-labels to match the scroll.
    //
    CPXYAxisSet *axisSet = (CPXYAxisSet *)self.graph.axisSet;
        if (coordinate == CPCoordinateX) {
            axisSet.yAxis.orthogonalCoordinateDecimal = newRange.location;
            axisSet.xAxis.titleLocation = CPDecimalFromFloat(newRange.doublePrecisionLocation +
                                                             (newRange.doublePrecisionLength / 2.0F));
        } else {
            axisSet.xAxis.orthogonalCoordinateDecimal = newRange.location;
            axisSet.yAxis.titleLocation = CPDecimalFromFloat(newRange.doublePrecisionLocation +
                                                             (newRange.doublePrecisionLength / 2.0F));
        }

    return newRange;
}

See: CPPlotSpace.h

Answer 3

All you have to do to fix the y axis after Answer 4 with the comment incl. ( newRange.doublePrecisionLocation is now newRange.locationDouble ) is to set plotSpace.globalYRange = plotSpace.yRange;