2

我的目标是在我的 UIView 上画一个空的圆形框，它应该显示为一个洞，以显示下面的内容。我通过覆盖 drawRect 方法来做到这一点，如下所示。这使我能够创建我的 holeRect 属性（它是一个 CGRect）大小的圆角矩形，将内部阴影放入其中并将其放置在我的视图上，清除（使用clearColor和CGContextSetBlendMode(context, kCGBlendModeSourceOut)）此框覆盖的区域并揭示了我的观点背后的内容（我从这个问题中获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，我找不到这样做的方法，也许我选择了错误的方法来做这件事，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);

}
4

2 回答 2

1

看看我对一个关于在 UIImageView 中打孔的问题给出的答案：

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

请注意，它的工作方式是 UIImageView 的 superview 层有一个子层来进行遮罩，从而打孔。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。正如我的书中所述，Core Animation 很简单：

http://www.aeth.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封装为一个图层，那么通过移动图层来为其设置动画是微不足道的。

于 2013-04-09T02:08:27.830 回答
0

按照您已经进行的设置，您要做的是将切口的位置存储在视图类（实现此drawRect方法的类）的实例变量中，并使用 NSTimer 定期更新位置。例如，在您的视图代码中，您可以像这样创建一个预定的计时器：

[NSTimer scheduledTimerWithTimeInterval:1.0/30.0 target:self selector:@selector(updateCutoutPosition) userInfo:nil repeats:YES];

然后实现更新方法：

- (void)updateCutoutPosition {
    // Do whatever you need to do to update the position of the cutout.
    [self setNeedsDisplay]; // Will cause drawRect to be called again soon.
}
于 2013-04-09T01:59:31.727 回答