将阴影放置到矩形中（drawRect：（CGRect）rect） [英] Put shadow to a rectangle (drawRect:(CGRect)rect)

问题描述

我用此代码制作了一个矩形，它可以正常工作：

I did a rectangle with this code and it works:

- (void)drawRect:(CGRect)rect{
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextAddRect(context, CGRectMake(60, 60, 100, 1));
    CGContextStrokePath(context);
}

但是现在我想放一个阴影，我尝试了一下：

But now i want to put a shadow, I tried with this:

NSShadow* theShadow = [[NSShadow alloc] init];
[theShadow setShadowOffset:NSMakeSize(10.0, -10.0)];
[theShadow setShadowBlurRadius:4.0];

但是xcode告诉我有关 NSMakeSize的信息：向不兼容的参数发送'int'输入'CGSize'

But xcode tell me about NSMakeSize : Sending 'int' to parameter of incompatible type 'CGSize'

关于阴影的正确形式是什么？
谢谢！

Which is the correct form about shadows? Thanks!!

推荐答案

您应该调用 CGContextSetShadow（...）函数在绘制应具有阴影的对象的函数之前。这是完整的代码：

You should invoke CGContextSetShadow(...) function before the functions that draw object that should have a shadow. Here is the complete code:

- (void)drawRect:(CGRect)rect {
    // define constants
    const CGFloat shadowBlur = 5.0f;
    const CGSize shadowOffset = CGSizeMake(10.0f, 10.0f);

    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetRGBStrokeColor(context, 1, 0, 0, 1);

    // Setup shadow parameters. Everithyng you draw after this line will be with shadow
    // To turn shadow off invoke CGContextSetShadowWithColor(...) with NULL for CGColorRef parameter.
    CGContextSetShadow(context, shadowOffset, shadowBlur);

    CGRect rectForShadow = CGRectMake(rect.origin.x, rect.origin.y, rect.size.width - shadowOffset.width - shadowBlur, rect.size.height - shadowOffset.height - shadowBlur);
    CGContextAddRect(context, rectForShadow);
    CGContextStrokePath(context);
}

备注：

我注意到您为 CGContextAddRect（context，CGRectMake（60，60，100，1））; 提供了一些随机值。您应该只在通过 rect 参数接收的矩形内绘制。

I have noticed that you provide some random values to CGContextAddRect(context, CGRectMake(60, 60, 100, 1));. You should draw only within the rectangle that you receive through rect parameter.

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