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, 0, 2*M_PI, 0); //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