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

1 #import <UIKit/UIKit.h>
2 
3 @interface KMDrawView : UIView
4 
5 @end

KMDrawView.m

 1 #import "KMDrawView.h"
 2 
 3 @interface KMDrawView ()
 4 - (void)drawFont;
 5 - (void)drawLine;
 6 - (void)drawCircle;
 7 - (void)drawRectangle;
 8 
 9 @end
10 
11 @implementation KMDrawView
12 
13 - (instancetype)initWithFrame:(CGRect)frame{
14     if (self=[super initWithFrame:frame]) {
15         self.backgroundColor = [UIColor colorWithWhite:0.7 alpha:1.0];
16     }
17     return self;
18 }
19 
20 - (void)drawRect:(CGRect)rect {
21     [self drawFont];
22     [self drawLine];
23     [self drawCircle];
24     [self drawRectangle];
25     
26     [super drawRect:rect];
27 }
28 
29 #pragma mark - 绘制『文字』、『线条』、『圆形』、『矩形』
30 - (void)drawFont {
31     NSDictionary *dicAttribute = @{
32                                    NSForegroundColorAttributeName : [UIColor brownColor],
33                                    NSFontAttributeName : [UIFont systemFontOfSize:18.0]
34                                    };
35     
36     [@"我是文字" drawInRect:CGRectMake(20.0, 20.0, 100.0, 30.0) withAttributes:dicAttribute];
37 }
38 
39 - (void)drawLine {
40     CGContextRef contextRef = UIGraphicsGetCurrentContext(); //获取绘制上下文对象实例
41     CGContextSetRGBStrokeColor(contextRef, 0.5, 0.5, 0.5, 1.0); //设置笔画颜色
42     CGContextSetLineWidth(contextRef, 2.0); //设置线条粗细大小
43     
44     CGContextMoveToPoint(contextRef, 20.0, 100.0); //设置直线的首端
45     CGContextAddLineToPoint(contextRef, 320.0, 100.0); //设置直线的末端
46     CGContextStrokePath(contextRef); //沿着要求的路径，开始绘制
47 }
48 
49 - (void)drawCircle {
50     CGContextRef contextRef = UIGraphicsGetCurrentContext(); //获取绘制上下文对象实例
51     CGContextSetRGBStrokeColor(contextRef, 1.0, 1.0, 1.0, 1.0); //设置笔画颜色
52     CGContextSetLineWidth(contextRef, 2.0); //设置线条粗细大小
53     
54     //voidCGContextAddArc(CGContextRef c,CGFloat x,CGFloat y,CGFloat radius,CGFloat startAngle,CGFloat endAngle,int clockwise)
55     //1弧度＝180°/π（≈57.3°）度
56     //360°＝360 * π/180＝2π弧度
57     //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。
58     CGContextAddArc(contextRef, 70.0, 200.0, 50.0, 0, 2*M_PI, 0); //添加一个圆；M_PI为180度
59     CGContextDrawPath(contextRef, kCGPathStroke); //绘制路径
60 }
61 
62 - (void)drawRectangle {
63     CGContextRef contextRef = UIGraphicsGetCurrentContext(); //获取绘制上下文对象实例
64     CGContextSetRGBStrokeColor(contextRef, 0.0, 0.0, 0.0, 1.0); //设置笔画颜色
65     CGContextSetLineWidth(contextRef, 2.0); //设置线条粗细大小
66     
67     CGContextAddRect(contextRef, CGRectMake(20.0, 300.0, 200.0, 100.0)); //设置矩形位置和宽高
68     CGContextStrokePath(contextRef); //沿着要求的路径，开始绘制
69 }
70 
71 @end

ViewController.h

1 #import <UIKit/UIKit.h>
2 
3 @interface ViewController : UIViewController
4 
5 
6 @end

ViewController.m

 1 #import "ViewController.h"
 2 #import "KMDrawView.h"
 3 
 4 @interface ViewController ()
 5 - (void)layoutUI;
 6 @end
 7 
 8 @implementation ViewController
 9 
10 - (void)viewDidLoad {
11     [super viewDidLoad];
12     
13     [self layoutUI];
14 }
15 
16 - (void)didReceiveMemoryWarning {
17     [super didReceiveMemoryWarning];
18     // Dispose of any resources that can be recreated.
19 }
20 
21 - (void)layoutUI {
22     KMDrawView *drawView = [[KMDrawView alloc] initWithFrame:self.view.frame];
23     [self.view addSubview:drawView];
24 }
25 
26 @end