在UIView类别中创建UIBezierPath.没有显示

Question

我试图在UIView类别中使用UIBezierPath创建一个三角形.但没有显示三角形.还得到一个:CGContextSetFillColorWithColor.所以我的问题是如何使用UIView类别制作三角形或任何路径.演示项目

#import "UIView+Bubble.h"
#import <QuartzCore/QuartzCore.h>

@implementation UIView (Bubble)

+(UIView *)makeBubble{
    UIView *customView = [[UIView alloc] init];
    customView.frame=CGRectMake(0, 0, 320, 500);
    UIBezierPath *triangle = [UIBezierPath bezierPath];
    [triangle moveToPoint:CGPointMake(100, 0)];
    [triangle addLineToPoint:CGPointMake(0, 100)];
    [triangle addLineToPoint:CGPointMake(200, 100)];
    [triangle closePath];
    [[UIColor blackColor] setFill];
    [triangle fill];
    customView.layer.shadowPath = [triangle CGPath];
    return customView;
}
@end

在ViewController.m中使用它像: -

- (void)viewDidLoad
{
    UIView *helpBubble=[UIView makeBubble];
    [self.view addSubview:helpBubble];
}

Answer 1

在UIView + Bubble.h类别中,UIBezierPath尝试在空上下文中绘制三角形.如果您想使用上面的UIBezierPath绘制形状,则必须将此代码放在drawRectView类的方法中.

另一方面,您可以创建一个新的上下文来绘制.您可以修改makeBubble方法,如下所示:

+(UIView *)makeBubble{
   // declare UIimageView, not UIView
   UIImageView *customView = [[UIImageView alloc] init];
   customView.frame=CGRectMake(0, 0, 320, 500);

   // create a new contex to draw
   UIGraphicsBeginImageContextWithOptions(CGSizeMake(200, 200), NO, 0);

   UIBezierPath *triangle = [UIBezierPath bezierPath];
   [triangle moveToPoint:CGPointMake(100, 0)];
   [triangle addLineToPoint:CGPointMake(0, 100)];
   [triangle addLineToPoint:CGPointMake(200, 100)];
   [triangle closePath];
   [[UIColor blackColor] setFill];
   [triangle fill];

   customView.image = UIGraphicsGetImageFromCurrentImageContext();

   UIGraphicsEndImageContext();

   return customView;
}

编辑:

为了使它动态,你可以传递一个cgRect参数,比如

+(UIView *)makeBubble:(CGRect)rect

也更改为customView.frame=rect;与UIGraphicsBeginImageContextWithOptions(rect.size, NO, 0);该方法内.并调用makeBubble:(CGRect)rect方法作为

UIView *helpBubble=[UIView makeBubble:/*your desire rect*/];

如果根据矩形计算得分,那将是很好的.