創建一個UIView的子類，重寫drawRect方法可以實現不規則形狀的View，這裏提供一個帶箭頭View的實現代碼：

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...");
        
    //獲取當前圖形,視圖推入堆棧的圖形,相當於你所要繪制圖形的圖紙
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    //
    [[UIColor whiteColor] set];
    //創建一個新的空圖形路徑
    CGContextBeginPath(ctx);
    
    NSLog(
 
@"開始繪制...");
    
    //起始位置坐標
    CGFloat origin_x = rect.origin.x;
    CGFloat origin_y = 10; //frame.origin.y + 10;
    //第一條線的位置坐標
    CGFloat line_1_x = rect.size.width - 20;
    CGFloat line_1_y = origin_y;
    //第二條線的位置坐標
    CGFloat line_2_x = line_1_x + 5;
    CGFloat line_2_y = rect.origin.y;
    //第三條線的位置坐標
    CGFloat line_3_x = line_2_x + 5;
    CGFloat line_3_y = line_1_y;
    //第四條線的位置坐標
    CGFloat line_4_x = rect.size.width;
    CGFloat line_4_y = line_1_y;
    //第五條線的位置坐標
    CGFloat line_5_x = rect.size.width;
    CGFloat line_5_y = rect.size.height;
    //第六條線的位置坐標
    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);
    
    //設置填充顏色
    UIColor *customColor = [UIColor colorWithWhite:0 alpha:0.8];
    CGContextSetFillColorWithColor(ctx, customColor.CGColor);
    CGContextFillPath(ctx);
}

@end

然後在ViewController中調用，查看結果

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

結果截圖：

控制臺打印結果：

控制臺打印的線程ID是相同的，說明drawRect的方法是在主線程調用的。

iOS重寫drawRect方法實現帶箭頭的View