如何畫一個餅圖, 來實現資料展示的視覺化

• PieChartView.h

#import <UIKit/UIKit.h>

@interface PieChartView : UIView

@end

• PieChartView.m

#import "PieChartView.h"

@implementation PieChartView

- (void)drawRect:(CGRect)rect {

    CGFloat w = self.bounds.size.width;
    CGFloat h = self.bounds.size.height
 
;

    //資料陣列
    NSArray *array = @[@25,@30,@45];
    //顏色陣列
    NSArray *colorArray = @[[UIColor redColor], [UIColor greenColor], [UIColor yellowColor]];

    CGContextRef ctx =UIGraphicsGetCurrentContext();

    //中心點
    CGPoint center = CGPointMake(w * 0.5, h * 0.5);
    //半徑
    CGFloat radius = w * 0.5 - 5
 
;

    //起點角度
    CGFloat startA = 0;
    //終點角度
    CGFloat endA = 0;
    //掃過角度範圍
    CGFloat angle = 0;

    for (int i = 0; i < array.count; i ++) {

        startA = endA;
        angle = [array[i] integerValue] / 100.0 * M_PI * 2;
        endA = startA + angle;

        //弧形路徑
        //clockwise: 是否是按照時鐘的方向旋轉(是否順時針)
 

        UIBezierPath *path = [UIBezierPath bezierPathWithArcCenter:center radius:radius startAngle:startA endAngle:endA clockwise:YES];
        //連線中心, 構成扇形
        [path addLineToPoint:center];

        //填充顏色
        [(UIColor *)colorArray[i] set];

        CGContextAddPath(ctx, path.CGPath);

        // 將上下文渲染到檢視
        CGContextFillPath(ctx);
    }
}

@end