直奔主题看演示效果：

代码：

ViewController.m

#import "ViewController.h"
#define ScreenWidth self.view.bounds.size.width
#define ScceenHeight self.view.bounds.size.height
@interface ViewController ()
@property (nonatomic,strong)UIButton * btn1,* btn2,* btn3 ,* btn4, * btn5;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    
    
    CGFloat btnWidth = (ScreenWidth-30)/3;
    CGFloat bigBtnHeight = btnWidth;
    CGFloat smallBtnHeight = (bigBtnHeight-5)*0.5;
    
    
    //    btn1
   _btn1 = [[UIButton alloc]initWithFrame:CGRectMake(10, 50, btnWidth, bigBtnHeight)];
    _btn1.backgroundColor = [UIColor redColor];
    [_btn1 setTitle:@"btn1" forState:UIControlStateNormal];
    [self.view addSubview:_btn1];
    
    

    CGSize size = CGSizeMake(10, 10);
    CAShapeLayer *maskLayer1 = [[CAShapeLayer alloc] init];
    UIBezierPath *maskPath1 = [UIBezierPath bezierPathWithRoundedRect:_btn1.bounds byRoundingCorners:UIRectCornerTopLeft | UIRectCornerBottomLeft cornerRadii:size];
    maskLayer1.frame = _btn1.bounds;
    maskLayer1.path = maskPath1.CGPath;
    _btn1.layer.mask = maskLayer1;
    
    
//    _btn4
    _btn4 = [[UIButton alloc]initWithFrame:CGRectMake(ScreenWidth-10-btnWidth, 50, btnWidth, bigBtnHeight)];
    _btn4.backgroundColor = [UIColor grayColor];
    [_btn4 setTitle:@"btn4" forState:UIControlStateNormal];
    
    [self.view addSubview:_btn4];
    
    CAShapeLayer * maskLayer4 = [[CAShapeLayer alloc]init];
    UIBezierPath * maskPath4 = [UIBezierPath bezierPathWithRoundedRect:_btn4.bounds byRoundingCorners:UIRectCornerTopRight | UIRectCornerBottomRight cornerRadii:size];
    maskLayer4.frame = _btn4.bounds;
    maskLayer4.path = maskPath4.CGPath;
    _btn4.layer.mask = maskLayer4;
    
//    _btn2
    
    _btn2 = [[UIButton alloc]initWithFrame:CGRectMake(btnWidth+15, 50, btnWidth, smallBtnHeight)];
    _btn2.backgroundColor = [UIColor greenColor];
    [_btn2 setTitle:@"btn2" forState:UIControlStateNormal];
    
    [self.view addSubview:_btn2];
    
//    _btn3
    
    _btn3 = [[UIButton alloc]initWithFrame:CGRectMake(btnWidth+15, 50+5+smallBtnHeight, btnWidth, smallBtnHeight)];
    _btn3.backgroundColor = [UIColor blueColor];
    [_btn3 setTitle:@"btn3" forState:UIControlStateNormal];
    
    [self.view addSubview:_btn3];
    
    
//    btn5
    _btn5 = [[UIButton alloc]initWithFrame:CGRectMake(50, 200, ScreenWidth-100, 100)];
    _btn5.backgroundColor = [UIColor purpleColor];
    [_btn5 setTitle:@"btn5" forState:UIControlStateNormal];
    [self.view addSubview:_btn5];
    
    CAShapeLayer * maskLayer5 = [[CAShapeLayer alloc]init];
    UIBezierPath * maskPath5 = [UIBezierPath bezierPathWithRoundedRect:_btn5.bounds byRoundingCorners:UIRectCornerTopRight | UIRectCornerBottomRight | UIRectCornerTopLeft | UIRectCornerBottomLeft cornerRadii:size];
    maskLayer5.frame = _btn5.bounds;
    maskLayer5.path = maskPath5.CGPath;
    _btn5.layer.mask = maskLayer5;
    

}




@end

其实，btn5的这种四个角都有圆角效果可以不用贝塞尔曲线写，直接用layer，如：

_btn5.layer.cornerRadius = 10;
_btn5.layer.masksToBounds = YES;