ios - 如何向 UILabel 添加三角形，使其看起来像工具提示？

Question

我想用一些自定义代码制作一个像 UILabel 这样的工具提示。我设法向 UILabel 添加一个三角形，但因为它超出了 UILabel 本身的边界(或框架)。它不是在屏幕上绘制的。

这是我的方法:

- (void) addTriangleTipToLayer: (CALayer *) targetLayer{
[targetLayer setBackgroundColor: [UIColor whiteColor].CGColor];

CGPoint startPoint = CGPointMake(0, targetLayer.frame.size.height);
CGPoint endPoint = CGPointMake(15, targetLayer.frame.size.height);
UIBezierPath *trianglePath = [UIBezierPath bezierPath];

CGFloat middleX = (startPoint.x + endPoint.x) / 2;
CGFloat middleY = 7.5 * tan(M_PI / 3);

CGPoint middlePoint = CGPointMake(middleX, -middleY);

[trianglePath moveToPoint:startPoint];
[trianglePath addLineToPoint:middlePoint];
[trianglePath addLineToPoint:endPoint];
[trianglePath closePath];
CGAffineTransform rotate = CGAffineTransformMakeRotation(180);
[trianglePath applyTransform:rotate];

CAShapeLayer *triangleLayer = [CAShapeLayer layer];
[triangleLayer setFillColor: [UIColor whiteColor].CGColor];
[triangleLayer setPath:trianglePath.CGPath];
[targetLayer addSublayer:triangleLayer];

}

我还将标签转换为图像内容，以用作 Google map 标记图标。这是我对此 UILabel 所做的其他事情。

UILabel *klabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 50, 20)];
[klabel setFont: [UIFont fontWithName:@"Roboto-Light" size:9]];
[klabel setText: @"Tower"];
// here I apply the add triangle function to the uilabel.layer
[self addTriangleTipToLayer:klabel.layer];
//set the label to fit text content before rendered as a image
[klabel sizeToFit];
//convert the uilabel to image content
UIGraphicsBeginImageContextWithOptions(klabel.bounds.size, NO, [[UIScreen mainScreen] scale]);
[klabel.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage * kicon = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// the rest of code is just use the image content as marker icon on google map.
kaliaMarker = [[GMSMarker alloc] init];
kaliaMarker.tappable = NO;
kaliaMarker.position = CLLocationCoordinate2DMake(21.283652, -157.836971);
kaliaMarker.infoWindowAnchor = CGPointMake(0.5, 0.5);
kaliaMarker.icon = kicon;
kaliaMarker.map = self.mapView;

targetLayer 是 myLabel.layer，这是我添加三角形的位置。问题是 middleY 从计算中是 -12.4 ，我猜它超出了我的 UILabel 的可见边界/框架，你只是看不到它。

我想知道我应该做什么，或者增加 UILabel 的可见部分以显示这个小三角形的正确方法是什么。

谢谢大家的帮助!

附注它应该看起来像这样。

但看起来是这样的。如果我将路径旋转 90 度，我可以看到半个三角形，它当然就在那里。所以对于180度来说，整个三角形都超出了边界，看不到。

Answer 1

这段稍微修改过的代码可以正常工作。我将该方法的参数更改为 UIView，以便我可以访问其背景颜色以使三角形具有相同的颜色，并使三角形点的 y 值与 View 的高度成比例。

- (void) addTriangleTipToLayer: (UIView *) view{
    CALayer *targetLayer = view.layer;
    [targetLayer setBackgroundColor: [UIColor whiteColor].CGColor];

    CGPoint startPoint = CGPointMake(0, targetLayer.frame.size.height);
    CGPoint endPoint = CGPointMake(15, targetLayer.frame.size.height);
    UIBezierPath *trianglePath = [UIBezierPath bezierPath];

    CGFloat middleX = (startPoint.x + endPoint.x) / 2;
    CGFloat middleY = targetLayer.frame.size.height * 1.8;

    CGPoint middlePoint = CGPointMake(middleX, middleY);

    [trianglePath moveToPoint:startPoint];
    [trianglePath addLineToPoint:middlePoint];
    [trianglePath addLineToPoint:endPoint];
    [trianglePath closePath];

    CAShapeLayer *triangleLayer = [CAShapeLayer layer];
    [triangleLayer setFillColor: view.backgroundColor.CGColor];
    [triangleLayer setPath:trianglePath.CGPath];
    [targetLayer addSublayer:triangleLayer];
}