使用 CGContextRef 进行简单内容绘制

摘要 : CGContextRef 功能强大，我们借助它可以画各种图形。这里所举例子只是简单内容绘制，冰山一角，对此感兴趣的朋友可以举一反三，实现各种酷炫效果。

效果如下：

KMDrawView.h

 #import <UIKit/UIKit.h>

 @interface KMDrawView : UIView

 @end

KMDrawView.m

 #import "KMDrawView.h"

 @interface KMDrawView ()
 - (void)drawFont;
 - (void)drawLine;
 - (void)drawCircle;
 - (void)drawRectangle;

 @end

 @implementation KMDrawView

 - (instancetype)initWithFrame:(CGRect)frame{
     if (self=[super initWithFrame:frame]) {
         self.backgroundColor = [UIColor colorWithWhite:0.7 alpha:1.0];
     }
     return self;
 }

 - (void)drawRect:(CGRect)rect {
     [self drawFont];
     [self drawLine];
     [self drawCircle];
     [self drawRectangle];

     [super drawRect:rect];
 }

 #pragma mark - 绘制『文字』、『线条』、『圆形』、『矩形』
 - (void)drawFont {
     NSDictionary *dicAttribute = @{
                                    NSForegroundColorAttributeName : [UIColor brownColor],
                                    NSFontAttributeName : [UIFont systemFontOfSize:18.0]
                                    };

     [@"我是文字" drawInRect:CGRectMake(20.0, 20.0, 100.0, 30.0) withAttributes:dicAttribute];
 }

 - (void)drawLine {
     CGContextRef contextRef = UIGraphicsGetCurrentContext(); //获取绘制上下文对象实例
     CGContextSetRGBStrokeColor(contextRef, 0.5, 0.5, 0.5, 1.0); //设置笔画颜色
     CGContextSetLineWidth(contextRef, 2.0); //设置线条粗细大小

     CGContextMoveToPoint(contextRef, 20.0, 100.0); //设置直线的首端
     CGContextAddLineToPoint(contextRef, 320.0, 100.0); //设置直线的末端
     CGContextStrokePath(contextRef); //沿着要求的路径，开始绘制
 }

 - (void)drawCircle {
     CGContextRef contextRef = UIGraphicsGetCurrentContext(); //获取绘制上下文对象实例
     CGContextSetRGBStrokeColor(contextRef, 1.0, 1.0, 1.0, 1.0); //设置笔画颜色
     CGContextSetLineWidth(contextRef, 2.0); //设置线条粗细大小

     //voidCGContextAddArc(CGContextRef c,CGFloat x,CGFloat y,CGFloat radius,CGFloat startAngle,CGFloat endAngle,int clockwise)
     //1弧度＝180°/π（≈57.3°）度
     //360°＝360 * π/180＝2π弧度
     //x,y为圆点坐标，radius半径，startAngle为开始的弧度，endAngle为结束的弧度，clockwise0为顺时针，1为逆时针。
     CGContextAddArc(contextRef, 70.0, 200.0, 50.0, , *M_PI, ); //添加一个圆；M_PI为180度
     CGContextDrawPath(contextRef, kCGPathStroke); //绘制路径
 }

 - (void)drawRectangle {
     CGContextRef contextRef = UIGraphicsGetCurrentContext(); //获取绘制上下文对象实例
     CGContextSetRGBStrokeColor(contextRef, 0.0, 0.0, 0.0, 1.0); //设置笔画颜色
     CGContextSetLineWidth(contextRef, 2.0); //设置线条粗细大小

     CGContextAddRect(contextRef, CGRectMake(20.0, 300.0, 200.0, 100.0)); //设置矩形位置和宽高
     CGContextStrokePath(contextRef); //沿着要求的路径，开始绘制
 }

 @end

ViewController.h

 #import <UIKit/UIKit.h>

 @interface ViewController : UIViewController

 @end

ViewController.m

 #import "ViewController.h"
 #import "KMDrawView.h"

 @interface ViewController ()
 - (void)layoutUI;
 @end

 @implementation ViewController

 - (void)viewDidLoad {
     [super viewDidLoad];

     [self layoutUI];
 }

 - (void)didReceiveMemoryWarning {
     [super didReceiveMemoryWarning];
     // Dispose of any resources that can be recreated.
 }

 - (void)layoutUI {
     KMDrawView *drawView = [[KMDrawView alloc] initWithFrame:self.view.frame];
     [self.view addSubview:drawView];
 }

 @end