iOS重写drawRect方法实现带箭头的View

创建一个UIView的子类，重写drawRect方法可以实现不规则形状的View，这里提供一个带箭头View的实现代码：

ArrowView.h

#import <UIKit/UIKit.h>

@interface ArrowView : UIView

@end

ArrowView.m

#import "ArrowView.h"

@implementation ArrowView

/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
    // Drawing code
}
*/

- (instancetype)init{

    self = [super init];
    if (self) {
        self.backgroundColor = [UIColor whiteColor];
    }
    return self;

}

- (instancetype)initWithFrame:(CGRect)frame{

    self = [super initWithFrame:frame];
    if (self) {
        self.backgroundColor = [UIColor whiteColor];
    }
    return self;

}

- (void)drawRect:(CGRect)rect{
    [super drawRect:rect];

    NSLog(@"正在drawRect...");

    //获取当前图形,视图推入堆栈的图形,相当于你所要绘制图形的图纸
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    //
    [[UIColor whiteColor] set];
    //创建一个新的空图形路径
    CGContextBeginPath(ctx);

    NSLog(@"开始绘制...");

    //起始位置坐标
    CGFloat origin_x = rect.origin.x;
    CGFloat origin_y = 10; //frame.origin.y + 10;
    //第一条线的位置坐标
    CGFloat line_1_x = rect.size.width - 20;
    CGFloat line_1_y = origin_y;
    //第二条线的位置坐标
    CGFloat line_2_x = line_1_x + 5;
    CGFloat line_2_y = rect.origin.y;
    //第三条线的位置坐标
    CGFloat line_3_x = line_2_x + 5;
    CGFloat line_3_y = line_1_y;
    //第四条线的位置坐标
    CGFloat line_4_x = rect.size.width;
    CGFloat line_4_y = line_1_y;
    //第五条线的位置坐标
    CGFloat line_5_x = rect.size.width;
    CGFloat line_5_y = rect.size.height;
    //第六条线的位置坐标
    CGFloat line_6_x = origin_x;
    CGFloat line_6_y = rect.size.height;

    CGContextMoveToPoint(ctx, origin_x, origin_y);

    CGContextAddLineToPoint(ctx, line_1_x, line_1_y);
    CGContextAddLineToPoint(ctx, line_2_x, line_2_y);
    CGContextAddLineToPoint(ctx, line_3_x, line_3_y);
    CGContextAddLineToPoint(ctx, line_4_x, line_4_y);
    CGContextAddLineToPoint(ctx, line_5_x, line_5_y);
    CGContextAddLineToPoint(ctx, line_6_x, line_6_y);

    CGContextClosePath(ctx);

    //设置填充颜色
    UIColor *customColor = [UIColor colorWithWhite:0 alpha:0.8];
    CGContextSetFillColorWithColor(ctx, customColor.CGColor);
    CGContextFillPath(ctx);
}

@end

然后在ViewController中调用，查看结果

ViewController.m

#import "ViewController.h"
#import "ArrowView.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    NSLog(@"begin...");

    ArrowView *view = [[ArrowView alloc] initWithFrame:CGRectMake(100, 100, 200, 80)];
    //[view setBackgroundColor:[UIColor orangeColor]];
    [self.view addSubview:view];

    NSLog(@"end...");
}

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

@end

结果截图：

控制台打印结果：

控制台打印的线程ID是相同的，说明drawRect的方法是在主线程调用的。