带有虚线的 UIView [英] UIView with a Dashed line

问题描述

我所拥有的:

为了创建这一行，我基本上有一个 UIView 并且我执行以下操作:

To create this line, I basically have an UIView and I do the following:

void setLayerToLineFromAToB(CALayer *layer, CGPoint a, CGPoint b, CGFloat lineWidth)
{
    CGPoint center = { 0.5 * (a.x + b.x), 0.5 * (a.y + b.y) };
    CGFloat length = sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y));
    CGFloat angle = atan2(a.y - b.y, a.x - b.x);

    layer.position = center;
    layer.bounds = (CGRect) { {0, 0}, { length + lineWidth, lineWidth } };
    layer.transform = CATransform3DMakeRotation(angle, 0, 0, 1);
}

注意:此代码是在 stackoverflow 上找到的，所以如果有人能给我参考，我将不胜感激.

我想要的:

好的，所以我唯一"需要的是在 UIView 上创建这个模式.我知道我可以使用 Quartz2D 做到这一点(一个简单的方法可以在 这里找到).但我想通过操作 CALayer 而不是去绘制方法来做到这一点.为什么?由于我在 UIView 上进行了转换，我无法使用 draw 方法正确绘制.

Ok so the "only" thing I need is to create this pattern on the UIView. I know I am able to do this using Quartz2D (a simple way to do it can be found here). But I want to do it by manipulating the CALayer and not going to to the draw method. Why? Because of the transformation I am making on my UIView, I am not able to draw correctly using the draw method.

编辑 1:

只是为了说明我的问题:

Just to illustrate my problem:

通常你拥有的是 UIView 然后你基本上只是在其中画一些东西(在这种情况下是一条简单的线).我找到的摆脱灰色"区域的解决方案是不绘制某些东西，而是转换 UIView 本身.它工作得很好，如果你想要一条完整的线，当你想要一条虚线时问题就来了.

Normally what you have is UIView and then you basically just draw something in it (in this case a simple line). The solution I found to get rid of the "gray" area, was to instead of drawing something, just transform the UIView itself. It work well, if you want a fully filled line, the problem comes when you want a dashed one.

推荐答案

注意:Prince 的代码确实帮了我大忙，所以我会给他 +10 的提示.但最后，我添加了我自己的代码.我还将为其添加一些上下文，以便对未来的读者有用

Note: The code from Prince did really help me out, so I will give him +10 for the tips. But in the end, I add to come with my own code. I will also add some context to it, so it can be useful for future readers

最终的代码是这样的:

-(void)updateLine{

      // Important, otherwise we will be adding multiple sub layers
      if ([[[self layer] sublayers] objectAtIndex:0])
        {
            self.layer.sublayers = nil;
        }

        CAShapeLayer *shapeLayer = [CAShapeLayer layer];
        [shapeLayer setBounds:self.bounds];
        [shapeLayer setPosition:self.center];
        [shapeLayer setFillColor:[[UIColor clearColor] CGColor]];
        [shapeLayer setStrokeColor:[[UIColor blackColor] CGColor]];
        [shapeLayer setLineWidth:3.0f];
        [shapeLayer setLineJoin:kCALineJoinRound];
        [shapeLayer setLineDashPattern:
        [NSArray arrayWithObjects:[NSNumber numberWithInt:10],
        [NSNumber numberWithInt:5],nil]];

        // Setup the path
        CGMutablePathRef path = CGPathCreateMutable();
        CGPathMoveToPoint(path, NULL, beginPoint.center.x, beginPoint.center.y);
        CGPathAddLineToPoint(path, NULL, endPoint.center.x, endPoint.center.y);

        [shapeLayer setPath:path];
        CGPathRelease(path);

        [[self layer] addSublayer:shapeLayer];
}

就我而言，beginPoint 和 endPoint 可由用户使用 KVO 移动.所以当其中一个移动时:

In my case, the beginPoint and endPoint are movable by the user, by using KVO. So when one of them moves:

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if ([keyPath isEqual:@"position"])
    {
        [self updateLine];
    }
}

我确实经常使用 Prince 的代码.我尝试了 draw: 方法，它在虚线之间添加了一条细线(有点奇怪......)，我也尝试了 initWithFrame:.他的代码本身未经任何修改，就会在控制台上给我这种错误:

I did play a lot with Prince's code. I tried on the draw: method, which add a thin line between the dashed line (a bit weird...) and I also tried on initWithFrame:. By itself his code, without any modifications, would give me this kind of errors on the console:

<Error>: CGContextSaveGState: invalid context 0x0
<Error>: CGContextSetLineWidth: invalid context 0x0
<Error>: CGContextSetLineJoin: invalid context 0x0
<Error>: CGContextSetLineCap: invalid context 0x0
<Error>: CGContextSetMiterLimit: invalid context 0x0
<Error>: CGContextSetFlatness: invalid context 0x0
<Error>: CGContextAddPath: invalid context 0x0
<Error>: CGContextDrawPath: invalid context 0x0
<Error>: CGContextRestoreGState: invalid context 0x0

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