如何用Core Plot绘制柱状图

 

Core Plot提供了柱状图的绘制，不足的是，只有垂直柱状图，没有提供水平柱状图。期待下一版本的实现。

1、新建Windows-base Application。加入对Core Plot框架的引用。这里我们假设使用了CorePlot SDK ，项目设置参考前一博文《Core Plot SDK的用法》。

2、新建ViewController，首先修改ViewController的头文件，importCorePlot.h，同时实现CPPlotDataSource协议，增加一个CPGraph变量：

#import <UIKit/UIKit.h>

#import <CorePlot/CorePlot.h>

 

@interface BarChartViewController : UIViewController<CPPlotDataSource>

{

@private

CPXYGraph *barChart;

}

 

@property(readwrite, retain, nonatomic) NSTimer *timer;

 

@end

3、具体实现如下：

-(void)viewDidAppear:(BOOL)animated

{

 

   // 为CPGraph指定主题

    barChart = [[CPXYGraph alloc] initWithFrame:CGRectZero];

CPTheme *theme = [CPTheme themeNamed:kCPDarkGradientTheme];

    [barChart applyTheme:theme];

//把self.view由UIView转变为CPGraphHostingView，因为UIView无法加载CPGraph

self.view=[[ CPGraphHostingView alloc ]initWithFrame :[ UIScreen mainScreen]. bounds ];

CPGraphHostingView*hostingView = (CPGraphHostingView *)self.view;

[hostingView setHostedGraph :barChart];

   

    // CPGraph边框：无

    barChart.plotAreaFrame.borderLineStyle = nil;

    barChart.plotAreaFrame.cornerRadius = 0.0f;

    // CPGraph四边不留白

    barChart.paddingLeft = 0.0f;

    barChart.paddingRight = 0.0f;

    barChart.paddingTop = 0.0f;

    barChart.paddingBottom = 0.0f;

//绘图区4边留白

    barChart.plotAreaFrame.paddingLeft = 70.0;

barChart.plotAreaFrame.paddingTop = 20.0;

barChart.plotAreaFrame.paddingRight = 20.0;

barChart.plotAreaFrame.paddingBottom = 80.0;

   

    //CPGraph标题

    barChart.title = @"GraphTitle";

//在SDK中CPMutableTextStyle不可用，用CPTextStyle替代

CPTextStyle*textStyle=[CPTextStyle textStyle];

//    CPMutableTextStyle*textStyle = [CPTextStyle textStyle];

    textStyle.color = [CPColor grayColor];

    textStyle.fontSize = 16.0f;

    barChart.titleTextStyle =textStyle;

    barChart.titleDisplacement = CGPointMake(0.0f, -20.0f);

    barChart.titlePlotAreaFrameAnchor = CPRectAnchorTop;

//绘图空间 plotspace

    CPXYPlotSpace *plotSpace= (CPXYPlotSpace *)barChart.defaultPlotSpace;

//绘图空间大小：Y：0-300，x：0-16

    plotSpace.yRange = [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat(0.0f) length:CPDecimalFromFloat(300.0f)];

    plotSpace.xRange = [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat(0.0f) length:CPDecimalFromFloat(16.0f)];

   

//坐标系

CPXYAxisSet *axisSet =(CPXYAxisSet *)barChart.axisSet;

//x轴：为坐标系的x轴

    CPXYAxis *x =axisSet.xAxis;

CPLineStyle*lineStyle=[[CPLineStyle alloc]init];

lineStyle.lineColor=[CPColor greenColor];

lineStyle.lineWidth=1.0f;

//x轴：线型设置

    x.axisLineStyle =lineStyle;

//大刻度线：线型设置

    x.majorTickLineStyle =lineStyle;

//大刻度线：长度

x.majorTickLength=10;

//小刻度线：无

    x.minorTickLineStyle =lineStyle;

//小刻度线：长度

x.minorTickLength=5;

//大刻度线间隔单位：5个单位

    x.majorIntervalLength = CPDecimalFromString(@"5");

//直角坐标：0

    x.orthogonalCoordinateDecimal = CPDecimalFromString(@"0");

//标题

x.title = @"XAxis";

//标题位置：7.5单位

    x.titleLocation = CPDecimalFromFloat(7.5f);

//向下偏移：55.0

x.titleOffset = 55.0f;

//y轴

CPXYAxis *y =axisSet.yAxis;

//y轴：线型设置

    y.axisLineStyle =lineStyle;

//y轴：线型设置

    y.majorTickLineStyle =lineStyle;

//y轴：不显示小刻度线

    y.minorTickLineStyle = nil;

//大刻度线间距：50单位

    y.majorIntervalLength = CPDecimalFromString(@"50");

//坐标原点：0

    y.orthogonalCoordinateDecimal = CPDecimalFromString(@"0");

//轴标题

y.title = @"YAxis";

y.titleOffset = 45.0f;

    y.titleLocation = CPDecimalFromFloat(150.0f);

    //第1个柱状图：黑色

    CPBarPlot *barPlot =[CPBarPlot tubularBarPlotWithColor:[CPColor darkGrayColor] horizontalBars:NO];

    barPlot.baseValue = CPDecimalFromString(@"1");

//数据源，必须实现CPPlotDataSource协议

    barPlot.dataSource = self;

//图形向左偏移：0.25

    barPlot.barOffset = -0.25f;

//id，根据此id来区分不同的plot，或者为不同plot提供不同数据源

    barPlot.identifier = @"BarPlot 1";

//添加图形到绘图空间

    [barChart addPlot:barPlot toPlotSpace:plotSpace];

   

    //第2个柱状图：蓝色

    barPlot = [CPBarPlot tubularBarPlotWithColor:[CPColor blueColor] horizontalBars:NO];

//数据源，必须实现CPPlotDataSource协议

    barPlot.dataSource = self;

//柱子的起始基线：即最下沿的y坐标

    barPlot.baseValue = CPDecimalFromString(@"1");

//图形向右偏移：0.25

    barPlot.barOffset = 0.25f;

//在SDK中，barCornerRadius被cornerRadius替代

barPlot.cornerRadius=2.0f;

    //barPlot.barCornerRadius= 2.0f;

//id，根据此id来区分不同的plot，或者为不同plot提供不同数据源

    barPlot.identifier = @"BarPlot 2";

//添加图形到绘图空间

    [barChart addPlot:barPlot toPlotSpace:plotSpace];

}

 

- (void)didReceiveMemoryWarning{

    [super didReceiveMemoryWarning]; //Releases the view if it doesn't have a superview

    // Releaseanything that's not essential, such as cached data

}

 

#pragmamark -

#pragmamark Plot Data Source Methods

//返回数据源的纪录数

-(NSUInteger)numberOfRecordsForPlot:(CPPlot *)plot {

    return 16;

}

//返回数据源的数据

-(NSNumber*)numberForPlot:(CPPlot *)plot field:(NSUInteger)fieldEnumrecordIndex:(NSUInteger)index

{

//返回类型是一个NSNumber

    NSDecimalNumber *num = nil;

//如果图形类型是“柱状图”

    if ( [plot isKindOfClass:[CPBarPlot class]] ) {

//根据情况，柱状图的每一点都需要返回两种数据：位置（x轴），长度（y轴）

switch ( fieldEnum) {

//x轴坐标（柱子位置）：

case CPBarPlotFieldBarLocation:

num = (NSDecimalNumber *)[NSDecimalNumber numberWithUnsignedInteger:index];

break;

//y轴坐标（柱子长度）：

//SDK中，枚举CPBarPlotField只有两个值CPBarPlotFieldBarLocation= 2, 或者CPBarPlotFieldBarLength   = 3

case CPBarPlotFieldBarLength:

//caseCPBarPlotFieldBarTip:

num = (NSDecimalNumber *)[NSDecimalNumber numberWithUnsignedInteger:(index+1)*(index+1)];

//对于第2个图形的点的y值，在第一个图形的基础上减去10

if ( [plot.identifier isEqual:@"BarPlot 2"] )

num = [num decimalNumberBySubtracting:[NSDecimalNumber decimalNumberWithString:@"10"]];

break;

}

    }

    return num;

}

 

-(CPFill *)barFillForBarPlot:(CPBarPlot *)barPlotrecordIndex:(NSNumber *)index;

{

return nil;

}

 

运行效果如下：