ios - 通过 CGMutablePathRef 动画绘制在 drawRect 中的框

Question

我的目标是在我的 UIView 上绘制一个空的圆形框，它应该显示为一个洞，以显示下面的内容。 我通过重写 drawRect 方法实现了这一点，如下所示。 这使我能够创建一个圆角矩形，其大小与我的 holeRect 属性(这是一个 CGRect)相同，将内部阴影放入其中并将其放置在我的 View 中，清除(使用 clearColor 和 < strong>CGContextSetBlendMode(context, kCGBlendModeSourceOut) ) 这个框覆盖的区域并揭示了我的观点背后的内容(我从 this 问题中提取了一些代码并对其进行了修改)。 现在我的问题是我必须用动画移动和调整这个矩形的大小，但我找不到这样做的方法，也许我选择了错误的方法来做这个但我不是很擅长绘画所以任何提示将不胜感激。

- (void)drawRect:(CGRect)rect
{



//I set the frame of my "holey" rect
CGRect bounds =  self.holeRect;
CGContextRef context = UIGraphicsGetCurrentContext();
CGFloat radius = 20;

//fill my whole view with gray
CGContextSetFillColorWithColor( context, [UIColor colorWithRed:.5 green:.5 blue:.5 alpha:.8].CGColor );
CGContextFillRect( context, rect );

// Create the "visible" path, which will be the shape that gets the inner shadow
// In this case it's just a rounded rect, but could be as complex as your want
CGMutablePathRef visiblePath = CGPathCreateMutable();
CGRect innerRect = CGRectInset(bounds, radius, radius);
CGPathMoveToPoint(visiblePath, NULL, innerRect.origin.x, bounds.origin.y);
CGPathAddLineToPoint(visiblePath, NULL, innerRect.origin.x + innerRect.size.width, bounds.origin.y);
CGPathAddArcToPoint(visiblePath, NULL, bounds.origin.x + bounds.size.width, bounds.origin.y, bounds.origin.x + bounds.size.width, innerRect.origin.y, radius);
CGPathAddLineToPoint(visiblePath, NULL, bounds.origin.x + bounds.size.width, innerRect.origin.y + innerRect.size.height);
CGPathAddArcToPoint(visiblePath, NULL,  bounds.origin.x + bounds.size.width, bounds.origin.y + bounds.size.height, innerRect.origin.x + innerRect.size.width, bounds.origin.y + bounds.size.height, radius);
CGPathAddLineToPoint(visiblePath, NULL, innerRect.origin.x, bounds.origin.y + bounds.size.height);
CGPathAddArcToPoint(visiblePath, NULL,  bounds.origin.x, bounds.origin.y + bounds.size.height, bounds.origin.x, innerRect.origin.y + innerRect.size.height, radius);
CGPathAddLineToPoint(visiblePath, NULL, bounds.origin.x, innerRect.origin.y);
CGPathAddArcToPoint(visiblePath, NULL,  bounds.origin.x, bounds.origin.y, innerRect.origin.x, bounds.origin.y, radius);
CGPathCloseSubpath(visiblePath);

// Fill this path
UIColor *aColor = [UIColor clearColor];
[aColor setFill];
CGContextAddPath(context, visiblePath);
CGContextSetBlendMode(context, kCGBlendModeSourceOut);
CGContextFillPath(context);


// Now create a larger rectangle, which we're going to subtract the visible path from
// and apply a shadow
CGMutablePathRef path = CGPathCreateMutable();
//(when drawing the shadow for a path whichs bounding box is not known pass "CGPathGetPathBoundingBox(visiblePath)" instead of "bounds" in the following line:)
//-42 cuould just be any offset > 0
CGPathAddRect(path, NULL, CGRectInset(bounds, -42, -42));

// Add the visible path (so that it gets subtracted for the shadow)
CGPathAddPath(path, NULL, visiblePath);
CGPathCloseSubpath(path);

// Add the visible paths as the clipping path to the context
CGContextAddPath(context, visiblePath);
CGContextClip(context);


// Now setup the shadow properties on the context
aColor = [UIColor colorWithRed:0.0f green:0.0f blue:0.0f alpha:0.5f];
CGContextSaveGState(context);
CGContextSetShadowWithColor(context, CGSizeMake(0.0f, 1.0f), 5.0f, [aColor CGColor]);

// Now fill the rectangle, so the shadow gets drawn
[aColor setFill];   
CGContextSaveGState(context);   
CGContextAddPath(context, path);
CGContextEOFillPath(context);

// Release the paths
//CGPathRelease(path);
CGPathRelease(visiblePath);

}

Answer 1

看看我对一个关于在 UIImageView 中打洞的问题给出的答案:

https://stackoverflow.com/a/8632731/341994

请注意，它的工作方式是 UIImageView 的 super View 层有一个子层，该子层进行 mask ，从而打洞。这意味着要为孔设置动画，您所要做的就是为该子层的移动设置动画。使用 Core Animation 很简单，如我的书中所述:

http://www.apeth.com/iOSBook/ch17.html#_using_a_cabasicanimation

换句话说，如果您可以将您正在做的所有事情都封装为一个层，那么通过移动该层来为其设置动画是微不足道的。