CorePlot: creating bands with mutable widths (chan

问题:

I would like to create a CorePlot graph with dynamic bands (changing as the time goes along), a little bit like this ugly drawing here (forgive me for the quality):

Basically the band colouring should change based on some values/criteria. The yellow band can be wider or thinner and so can the white and green band. In other words these bands need to have dynamic width

This is the current way I set the y graph band colouring, however if I dynamically change it it does not work as it changes them all (I just want to change the band dynamically in a specific area of the graph and not all of it).

Any idea how I can achieve this?

This is the code related to the band:

CPTFill *whitebandFill = [CPTFill fillWithColor:[[CPTColor whiteColor] colorWithAlphaComponent:0.5]];
CPTFill *greenbandFill = [CPTFill fillWithColor:[[CPTColor greenColor] colorWithAlphaComponent:0.5]];
CPTFill *redbandFill = [CPTFill fillWithColor:[[CPTColor redColor] colorWithAlphaComponent:0.75]];

 [y addBackgroundLimitBand:[CPTLimitBand limitBandWithRange:[CPTPlotRange plotRangeWithLocationDecimal:CPTDecimalFromDouble(0.0) lengthDecimal:CPTDecimalFromDouble(500.0)] fill:whitebandFill]];
[y addBackgroundLimitBand:[CPTLimitBand limitBandWithRange:[CPTPlotRange plotRangeWithLocationDecimal:CPTDecimalFromDouble(500.0) lengthDecimal:CPTDecimalFromDouble(750.0)] fill:greenbandFill]];

 [y addBackgroundLimitBand:[CPTLimitBand limitBandWithRange:[CPTPlotRange plotRangeWithLocationDecimal:CPTDecimalFromDouble(750.0) lengthDecimal:CPTDecimalFromDouble(1024.0)] fill:redbandFill]];

This is my complete current source code:

self.data = [[NSMutableArray alloc] initWithCapacity:100];
self.allData = [[NSMutableArray alloc] init];

// Create a CPTGraph object and add to hostView
self.graph = [[CPTXYGraph alloc] initWithFrame:self.graphHostView.bounds];
self.graphHostView.hostedGraph = self.graph;

CPTMutableTextStyle *titleStyle = [CPTMutableTextStyle textStyle];
titleStyle.color = [CPTColor blackColor];
titleStyle.fontName = @"Futura";
titleStyle.fontSize = 12.0f;

//////////
// Axes
// Label x axis with a fixed interval policy
CPTXYAxisSet *axisSet = (CPTXYAxisSet *)self.graph.axisSet;
CPTXYAxis *x          = axisSet.xAxis;
x.separateLayers              = NO;
x.title                       = @"X Axis";
x.titleTextStyle              = titleStyle;

colorWithAlphaComponent:CPTFloat(0.1)], [[CPTColor greenColor] colorWithAlphaComponent:CPTFloat(0.1)]]; x.delegate = self;

CPTXYAxis *y = axisSet.yAxis;
y.labelingPolicy        = CPTAxisLabelingPolicyAutomatic;
y.separateLayers        = YES;
y.majorTickLocations = [NSSet setWithObjects:
                        [NSDecimalNumber numberWithDouble:0],
                        [NSDecimalNumber numberWithDouble:300],
                        nil];

y.title                 = @"Y Axis";
y.titleTextStyle        = titleStyle;

colorWithAlphaComponent:CPTFloat(0.3)], [NSNull null]]; y.delegate = self;

CPTFill *whitebandFill = [CPTFill fillWithColor:[[CPTColor whiteColor] colorWithAlphaComponent:0.5]];
CPTFill *greenbandFill = [CPTFill fillWithColor:[[CPTColor greenColor] colorWithAlphaComponent:0.5]];
CPTFill *redbandFill = [CPTFill fillWithColor:[[CPTColor redColor] colorWithAlphaComponent:0.75]];

 [y addBackgroundLimitBand:[CPTLimitBand limitBandWithRange:[CPTPlotRange plotRangeWithLocationDecimal:CPTDecimalFromDouble(0.0) lengthDecimal:CPTDecimalFromDouble(500.0)] fill:whitebandFill]];
[y addBackgroundLimitBand:[CPTLimitBand limitBandWithRange:[CPTPlotRange plotRangeWithLocationDecimal:CPTDecimalFromDouble(500.0) lengthDecimal:CPTDecimalFromDouble(750.0)] fill:greenbandFill]];

 [y addBackgroundLimitBand:[CPTLimitBand limitBandWithRange:[CPTPlotRange plotRangeWithLocationDecimal:CPTDecimalFromDouble(750.0) lengthDecimal:CPTDecimalFromDouble(1024.0)] fill:redbandFill]];

self.graph.axisSet.axes = @[x, y];

回答1:

Limit bands always extend across the plot area in strait lines. You can draw more complex shapes by using additional plots. Set the areaFill to draw a fill between the plot line and the areaBaseValue.