在Swift for iOS中沿圆形路径绘制文本
我正在寻找一些关于如何使用Swift2为iOS9在圆圈边缘绘制简单单行字符串的最新帮助/提示。我看到涉及旧ObjC片段的相当陈旧的例子，并且仅限于OS X。这在iOS中是否可以在自定义UIView子类的drawRect()方法中使用？
5 个答案:
答案 0 :(得分：116)
我打算说“你有什么尝试？”，但这是星期五下午，我提早下班，所以我借机翻译了我的旧ObjC代码。在这里，适合游乐场。把它放在你的UIView中应该是微不足道的。
斯威夫特2
请参阅下面的Swift 3＆amp; Swift 4更新......
import UIKit
func centreArcPerpendicularText(str: String, context: CGContextRef, radius r: CGFloat, angle theta: CGFloat, colour c: UIColor, font: UIFont, clockwise: Bool){
// *******************************************************
// This draws the String str around an arc of radius r,
// with the text centred at polar angle theta
// *******************************************************
let l = str.characters.count
let attributes = [NSFontAttributeName: font]
var characters: [String] = [] // This will be an array of single character strings, each character in str
var arcs: [CGFloat] = [] // This will be the arcs subtended by each character
var totalArc: CGFloat = 0 // ... and the total arc subtended by the string
// Calculate the arc subtended by each letter and their total
for i in 0 ..< l {
characters += [String(str[str.startIndex.advancedBy(i)])]
arcs += [chordToArc(characters[i].sizeWithAttributes(attributes).width, radius: r)]
totalArc += arcs[i]
}
// Are we writing clockwise (right way up at 12 o'clock, upside down at 6 o'clock)
// or anti-clockwise (right way up at 6 o'clock)?
let direction: CGFloat = clockwise ? -1 : 1
let slantCorrection = clockwise ? -CGFloat(M_PI_2) : CGFloat(M_PI_2)
// The centre of the first character will then be at
// thetaI = theta - totalArc / 2 + arcs[0] / 2
// But we add the last term inside the loop
var thetaI = theta - direction * totalArc / 2
for i in 0 ..< l {
thetaI += direction * arcs[i] / 2
// Call centerText with each character in turn.
// Remember to add +/-90º to the slantAngle otherwise
// the characters will "stack" round the arc rather than "text flow"
centreText(characters[i], context: context, radius: r, angle: thetaI, colour: c, font: font, slantAngle: thetaI + slantCorrection)
// The centre of the next character will then be at
// thetaI = thetaI + arcs[i] / 2 + arcs[i + 1] / 2
// but again we leave the last term to the start of the next loop...
thetaI += direction * arcs[i] / 2
}
}
func chordToArc(chord: CGFloat, radius: CGFloat) -> CGFloat {
// *******************************************************
// Simple geometry
// *******************************************************
return 2 * asin(chord / (2 * radius))
}
func centreText(str: String, context: CGContextRef, radius r:CGFloat, angle theta: CGFloat, colour c: UIColor, font: UIFont, slantAngle: CGFloat) {
// *******************************************************
// This draws the String str centred at the position
// specified by the polar coordinates (r, theta)
// i.e. the x= r * cos(theta) y= r * sin(theta)
// and rotated by the angle slantAngle
// *******************************************************
// Set the text attributes
let attributes = [NSForegroundColorAttributeName: c,
NSFontAttributeName: font]
// Save the context
CGContextSaveGState(context)
// Undo the inversion of the Y-axis (or the text goes backwards!)
CGContextScaleCTM(context, 1, -1)
// Move the origin to the centre of the text (negating the y-axis manually)
CGContextTranslateCTM(context, r * cos(theta), -(r * sin(theta)))
// Rotate the coordinate system
CGContextRotateCTM(context, -slantAngle)
// Calculate the width of the text
let offset = str.sizeWithAttributes(attributes)
// Move the origin by half the size of the text
CGContextTranslateCTM (context, -offset.width / 2, -offset.height / 2) // Move the origin to the centre of the text (negating the y-axis manually)
// Draw the text
str.drawAtPoint(CGPointZero, withAttributes: attributes)
// Restore the context
CGContextRestoreGState(context)
}
// *******************************************************
// Playground code to test
// *******************************************************
let size = CGSize(width: 256, height: 256)
UIGraphicsBeginImageContextWithOptions(size, true, 0.0)
let context = UIGraphicsGetCurrentContext()!
// *******************************************************************
// Scale & translate the context to have 0,0
// at the centre of the screen maths convention
// Obviously change your origin to suit...
// *******************************************************************
CGContextTranslateCTM (context, size.width / 2, size.height / 2)
CGContextScaleCTM (context, 1, -1)
centreArcPerpendicularText("Hello round world", context: context, radius: 100, angle: 0, colour: UIColor.redColor(), font: UIFont.systemFontOfSize(16), clockwise: true)
centreArcPerpendicularText("Anticlockwise", context: context, radius: 100, angle: CGFloat(-M_PI_2), colour: UIColor.redColor(), font: UIFont.systemFontOfSize(16), clockwise: false)
centreText("Hello flat world", context: context, radius: 0, angle: 0 , colour: UIColor.yellowColor(), font: UIFont.systemFontOfSize(16), slantAngle: CGFloat(M_PI_4))
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
输出是：
更新的 顺时针/逆时针添加＆amp;直接的例子。
更新Swift 3
func centreArcPerpendicular(text str: String, context: CGContext, radius r: CGFloat, angle theta: CGFloat, colour c: UIColor, font: UIFont, clockwise: Bool){
// *******************************************************
// This draws the String str around an arc of radius r,
// with the text centred at polar angle theta
// *******************************************************
let l = str.characters.count
let attributes = [NSFontAttributeName: font]
let characters: [String] = str.characters.map { String($0) } // An array of single character strings, each character in str
var arcs: [CGFloat] = [] // This will be the arcs subtended by each character
var totalArc: CGFloat = 0 // ... and the total arc subtended by the string
// Calculate the arc subtended by each letter and their total
for i in 0 ..< l {
arcs += [chordToArc(characters[i].size(attributes: attributes).width, radius: r)]
totalArc += arcs[i]
}
// Are we writing clockwise (right way up at 12 o'clock, upside down at 6 o'clock)
// or anti-clockwise (right way up at 6 o'clock)?
let direction: CGFloat = clockwise ? -1 : 1
let slantCorrection = clockwise ? -CGFloat(M_PI_2) : CGFloat(M_PI_2)
// The centre of the first character will then be at
// thetaI = theta - totalArc / 2 + arcs[0] / 2
// But we add the last term inside the loop
var thetaI = theta - direction * totalArc / 2
for i in 0 ..< l {
thetaI += direction * arcs[i] / 2
// Call centerText with each character in turn.
// Remember to add +/-90º to the slantAngle otherwise
// the characters will "stack" round the arc rather than "text flow"
centre(text: characters[i], context: context, radius: r, angle: thetaI, colour: c, font: font, slantAngle: thetaI + slantCorrection)
// The centre of the next character will then be at
// thetaI = thetaI + arcs[i] / 2 + arcs[i + 1] / 2
// but again we leave the last term to the start of the next loop...
thetaI += direction * arcs[i] / 2
}
}
func chordToArc(_ chord: CGFloat, radius: CGFloat) -> CGFloat {
// *******************************************************
// Simple geometry
// *******************************************************
return 2 * asin(chord / (2 * radius))
}
func centre(text str: String, context: CGContext, radius r:CGFloat, angle theta: CGFloat, colour c: UIColor, font: UIFont, slantAngle: CGFloat) {
// *******************************************************
// This draws the String str centred at the position
// specified by the polar coordinates (r, theta)
// i.e. the x= r * cos(theta) y= r * sin(theta)
// and rotated by the angle slantAngle
// *******************************************************
// Set the text attributes
let attributes = [NSForegroundColorAttributeName: c,
NSFontAttributeName: font]
// Save the context
context.saveGState()
// Undo the inversion of the Y-axis (or the text goes backwards!)
context.scaleBy(x: 1, y: -1)
// Move the origin to the centre of the text (negating the y-axis manually)
context.translateBy(x: r * cos(theta), y: -(r * sin(theta)))
// Rotate the coordinate system
context.rotate(by: -slantAngle)
// Calculate the width of the text
let offset = str.size(attributes: attributes)
// Move the origin by half the size of the text
context.translateBy (x: -offset.width / 2, y: -offset.height / 2) // Move the origin to the centre of the text (negating the y-axis manually)
// Draw the text
str.draw(at: CGPoint(x: 0, y: 0), withAttributes: attributes)
// Restore the context
context.restoreGState()
}
// *******************************************************
// Playground code to test
// *******************************************************
let size = CGSize(width: 256, height: 256)
UIGraphicsBeginImageContextWithOptions(size, true, 0.0)
let context = UIGraphicsGetCurrentContext()!
// *******************************************************************
// Scale & translate the context to have 0,0
// at the centre of the screen maths convention
// Obviously change your origin to suit...
// *******************************************************************
context.translateBy (x: size.width / 2, y: size.height / 2)
context.scaleBy (x: 1, y: -1)
centreArcPerpendicular(text: "Hello round world", context: context, radius: 100, angle: 0, colour: UIColor.red, font: UIFont.systemFont(ofSize: 16), clockwise: true)
centreArcPerpendicular(text: "Anticlockwise", context: context, radius: 100, angle: CGFloat(-M_PI_2), colour: UIColor.red, font: UIFont.systemFont(ofSize: 16), clockwise: false)
centre(text: "Hello flat world", context: context, radius: 0, angle: 0 , colour: UIColor.yellow, font: UIFont.systemFont(ofSize: 16), slantAngle: CGFloat(M_PI_4))
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
Swift 4
然而，又一次微小的变化，这次修复了M_PI的弃用，String放弃.characters，.size(withAttributes...中的参数标签更改以及文本属性的更改到NSAttributedStringKey enum ...
import UIKit
func centreArcPerpendicular(text str: String, context: CGContext, radius r: CGFloat, angle theta: CGFloat, colour c: UIColor, font: UIFont, clockwise: Bool){
// *******************************************************
// This draws the String str around an arc of radius r,
// with the text centred at polar angle theta
// *******************************************************
let characters: [String] = str.map { String($0) } // An array of single character strings, each character in str
let l = characters.count
let attributes = [NSAttributedStringKey.font: font]
var arcs: [CGFloat] = [] // This will be the arcs subtended by each character
var totalArc: CGFloat = 0 // ... and the total arc subtended by the string
// Calculate the arc subtended by each letter and their total
for i in 0 ..< l {
arcs += [chordToArc(characters[i].size(withAttributes: attributes).width, radius: r)]
totalArc += arcs[i]
}
// Are we writing clockwise (right way up at 12 o'clock, upside down at 6 o'clock)
// or anti-clockwise (right way up at 6 o'clock)?
let direction: CGFloat = clockwise ? -1 : 1
let slantCorrection: CGFloat = clockwise ? -.pi / 2 : .pi / 2
// The centre of the first character will then be at
// thetaI = theta - totalArc / 2 + arcs[0] / 2
// But we add the last term inside the loop
var thetaI = theta - direction * totalArc / 2
for i in 0 ..< l {
thetaI += direction * arcs[i] / 2
// Call centerText with each character in turn.
// Remember to add +/-90º to the slantAngle otherwise
// the characters will "stack" round the arc rather than "text flow"
centre(text: characters[i], context: context, radius: r, angle: thetaI, colour: c, font: font, slantAngle: thetaI + slantCorrection)
// The centre of the next character will then be at
// thetaI = thetaI + arcs[i] / 2 + arcs[i + 1] / 2
// but again we leave the last term to the start of the next loop...
thetaI += direction * arcs[i] / 2
}
}
func chordToArc(_ chord: CGFloat, radius: CGFloat) -> CGFloat {
// *******************************************************
// Simple geometry
// *******************************************************
return 2 * asin(chord / (2 * radius))
}
func centre(text str: String, context: CGContext, radius r: CGFloat, angle theta: CGFloat, colour c: UIColor, font: UIFont, slantAngle: CGFloat) {
// *******************************************************
// This draws the String str centred at the position
// specified by the polar coordinates (r, theta)
// i.e. the x= r * cos(theta) y= r * sin(theta)
// and rotated by the angle slantAngle
// *******************************************************
// Set the text attributes
let attributes = [NSAttributedStringKey.foregroundColor: c, NSAttributedStringKey.font: font]
//let attributes = [NSForegroundColorAttributeName: c, NSFontAttributeName: font]
// Save the context
context.saveGState()
// Undo the inversion of the Y-axis (or the text goes backwards!)
context.scaleBy(x: 1, y: -1)
// Move the origin to the centre of the text (negating the y-axis manually)
context.translateBy(x: r * cos(theta), y: -(r * sin(theta)))
// Rotate the coordinate system
context.rotate(by: -slantAngle)
// Calculate the width of the text
let offset = str.size(withAttributes: attributes)
// Move the origin by half the size of the text
context.translateBy (x: -offset.width / 2, y: -offset.height / 2) // Move the origin to the centre of the text (negating the y-axis manually)
// Draw the text
str.draw(at: CGPoint(x: 0, y: 0), withAttributes: attributes)
// Restore the context
context.restoreGState()
}
// *******************************************************
// Playground code to test
// *******************************************************
let size = CGSize(width: 256, height: 256)
UIGraphicsBeginImageContextWithOptions(size, true, 0.0)
let context = UIGraphicsGetCurrentContext()!
// *******************************************************************
// Scale & translate the context to have 0,0
// at the centre of the screen maths convention
// Obviously change your origin to suit...
// *******************************************************************
context.translateBy (x: size.width / 2, y: size.height / 2)
context.scaleBy(x: 1, y: -1)
centreArcPerpendicular(text: "Hello round world", context: context, radius: 100, angle: 0, colour: UIColor.red, font: UIFont.systemFont(ofSize: 16), clockwise: true)
centreArcPerpendicular(text: "Anticlockwise", context: context, radius: 100, angle: CGFloat(-M_PI_2), colour: UIColor.red, font: UIFont.systemFont(ofSize: 16), clockwise: false)
centre(text: "Hello flat world", context: context, radius: 0, angle: 0 , colour: UIColor.yellow, font: UIFont.systemFont(ofSize: 16), slantAngle: .pi / 4)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
更新以显示在UIView中使用
评论员@RitvikUpadhyaya询问如何在UIView中做到这一点 - 显而易见的老手，但也许不是初学者。诀窍是使用UIGraphicsGetCurrentContext 获取正确的上下文，而无需调用UIGraphicsBeginImageContextWithOptions（它会覆盖UIView的上下文作为当前上下文） - 因此您的UIView应如下所示：
class MyView: UIView {
override func draw(_ rect: CGRect) {
guard let context = UIGraphicsGetCurrentContext() else { return }
let size = self.bounds.size
context.translateBy (x: size.width / 2, y: size.height / 2)
context.scaleBy (x: 1, y: -1)
centreArcPerpendicular(text: "Hello round world", context: context, radius: 100, angle: 0, colour: UIColor.red, font: UIFont.systemFont(ofSize: 16), clockwise: true)
centreArcPerpendicular(text: "Anticlockwise", context: context, radius: 100, angle: CGFloat(-M_PI_2), colour: UIColor.red, font: UIFont.systemFont(ofSize: 16), clockwise: false)
centre(text: "Hello flat world", context: context, radius: 0, angle: 0 , colour: UIColor.yellow, font: UIFont.systemFont(ofSize: 16), slantAngle: CGFloat(M_PI_4))
}
}
答案 1 :(得分：28)
@IBDesignable对于循环路径上的UILabel
首先，我想我们都同意@Grimxn是男人！他的解决方案踢了屁股。我接受了他的工作，并将其重构为一个自定义的UILabel控件，您可以在Storyboard上进行设置和编辑。如果你们看我的视频，你知道我有多喜欢做这些东西！
自定义UILabel的Swift 3代码
import UIKit
@IBDesignable
class UILabelX: UILabel {
// *******************************************************
// DEFINITIONS (Because I'm not brilliant and I'll forget most this tomorrow.)
// Radius: A straight line from the center to the circumference of a circle.
// Circumference: The distance around the edge (outer line) the circle.
// Arc: A part of the circumference of a circle. Like a length or section of the circumference.
// Theta: A label or name that represents an angle.
// Subtend: A letter has a width. If you put the letter on the circumference, the letter's width
// gives you an arc. So now that you have an arc (a length on the circumference) you can
// use that to get an angle. You get an angle when you draw a line from the center of the
// circle to each end point of your arc. So "subtend" means to get an angle from an arc.
// Chord: A line segment connecting two points on a curve. If you have an arc then there is a
// start point and an end point. If you draw a straight line from start point to end point
// then you have a "chord".
// sin: (Super simple/incomplete definition) Or "sine" takes an angle in degrees and gives you a number.
// asin: Or "asine" takes a number and gives you an angle in degrees. Opposite of sine.
// More complete definition: http://www.mathsisfun.com/sine-cosine-tangent.html
// cosine: Also takes an angle in degrees and gives you another number from using the two radiuses (radii).
// *******************************************************
@IBInspectable var angle: CGFloat = 1.6
@IBInspectable var clockwise: Bool = true
override func draw(_ rect: CGRect) {
centreArcPerpendicular()
}
/**
This draws the self.text around an arc of radius r,
with the text centred at polar angle theta
*/
func centreArcPerpendicular() {
guard let context = UIGraphicsGetCurrentContext() else { return }
let str = self.text ?? ""
let size = self.bounds.size
context.translateBy(x: size.width / 2, y: size.height / 2)
let radius = getRadiusForLabel()
let l = str.characters.count
let attributes: [String : Any] = [NSFontAttributeName: self.font]
let characters: [String] = str.characters.map { String($0) } // An array of single character strings, each character in str
var arcs: [CGFloat] = [] // This will be the arcs subtended by each character
var totalArc: CGFloat = 0 // ... and the total arc subtended by the string
// Calculate the arc subtended by each letter and their total
for i in 0 ..< l {
arcs += [chordToArc(characters[i].size(attributes: attributes).width, radius: radius)]
totalArc += arcs[i]
}
// Are we writing clockwise (right way up at 12 o'clock, upside down at 6 o'clock)
// or anti-clockwise (right way up at 6 o'clock)?
let direction: CGFloat = clockwise ? -1 : 1
let slantCorrection = clockwise ? -CGFloat(M_PI_2) : CGFloat(M_PI_2)
// The centre of the first character will then be at
// thetaI = theta - totalArc / 2 + arcs[0] / 2
// But we add the last term inside the loop
var thetaI = angle - direction * totalArc / 2
for i in 0 ..< l {
thetaI += direction * arcs[i] / 2
// Call centre with each character in turn.
// Remember to add +/-90º to the slantAngle otherwise
// the characters will "stack" round the arc rather than "text flow"
centre(text: characters[i], context: context, radius: radius, angle: thetaI, slantAngle: thetaI + slantCorrection)
// The centre of the next character will then be at
// thetaI = thetaI + arcs[i] / 2 + arcs[i + 1] / 2
// but again we leave the last term to the start of the next loop...
thetaI += direction * arcs[i] / 2
}
}
func chordToArc(_ chord: CGFloat, radius: CGFloat) -> CGFloat {
// *******************************************************
// Simple geometry
// *******************************************************
return 2 * asin(chord / (2 * radius))
}
/**
This draws the String str centred at the position
specified by the polar coordinates (r, theta)
i.e. the x= r * cos(theta) y= r * sin(theta)
and rotated by the angle slantAngle
*/
func centre(text str: String, context: CGContext, radius r:CGFloat, angle theta: CGFloat, slantAngle: CGFloat) {
// Set the text attributes
let attributes = [NSForegroundColorAttributeName: self.textColor,
NSFontAttributeName: self.font] as [String : Any]
// Save the context
context.saveGState()
// Move the origin to the centre of the text (negating the y-axis manually)
context.translateBy(x: r * cos(theta), y: -(r * sin(theta)))
// Rotate the coordinate system
context.rotate(by: -slantAngle)
// Calculate the width of the text
let offset = str.size(attributes: attributes)
// Move the origin by half the size of the text
context.translateBy(x: -offset.width / 2, y: -offset.height / 2) // Move the origin to the centre of the text (negating the y-axis manually)
// Draw the text
str.draw(at: CGPoint(x: 0, y: 0), withAttributes: attributes)
// Restore the context
context.restoreGState()
}
func getRadiusForLabel() -> CGFloat {
// Imagine the bounds of this label will have a circle inside it.
// The circle will be as big as the smallest width or height of this label.
// But we need to fit the size of the font on the circle so make the circle a little
// smaller so the text does not get drawn outside the bounds of the circle.
let smallestWidthOrHeight = min(self.bounds.size.height, self.bounds.size.width)
let heightOfFont = self.text?.size(attributes: [NSFontAttributeName: self.font]).height ?? 0
// Dividing the smallestWidthOrHeight by 2 gives us the radius for the circle.
return (smallestWidthOrHeight/2) - heightOfFont + 5
}
}
故事板上的用法示例
我所做的改变
- 我删除了现在可以直接从标签上获取的参数。
- 我确实不是三角学中最聪明的，并且在我这个年纪已经忘记了很多，所以我包含了所有相关的定义，所以我可以开始理解@Grimxn的光彩。
- 角度和顺时针设置现在是您可以在属性检查器中调整的属性。
- 我现在从标签的大小创建半径。
- 将一些标准格式的注释放在函数上，这样就可以获得OPTION + CLICK函数的弹出窗口。
我见过的问题
我鼓励您编辑以上内容以改进它。
- 我不知道为什么，但有时标签仍然会在其他控件上呈现，即使它在文档大纲中落后于它们。
答案 2 :(得分：9)
始终采用相同的实施方式，但针对 Swift 4
进行了调整import UIKit
@IBDesignable
class CircularLabel: UILabel {
// *******************************************************
// DEFINITIONS (Because I'm not brilliant and I'll forget most this tomorrow.)
// Radius: A straight line from the center to the circumference of a circle.
// Circumference: The distance around the edge (outer line) the circle.
// Arc: A part of the circumference of a circle. Like a length or section of the circumference.
// Theta: A label or name that represents an angle.
// Subtend: A letter has a width. If you put the letter on the circumference, the letter's width
// gives you an arc. So now that you have an arc (a length on the circumference) you can
// use that to get an angle. You get an angle when you draw a line from the center of the
// circle to each end point of your arc. So "subtend" means to get an angle from an arc.
// Chord: A line segment connecting two points on a curve. If you have an arc then there is a
// start point and an end point. If you draw a straight line from start point to end point
// then you have a "chord".
// sin: (Super simple/incomplete definition) Or "sine" takes an angle in degrees and gives you a number.
// asin: Or "asine" takes a number and gives you an angle in degrees. Opposite of sine.
// More complete definition: http://www.mathsisfun.com/sine-cosine-tangent.html
// cosine: Also takes an angle in degrees and gives you another number from using the two radiuses (radii).
// *******************************************************
@IBInspectable var angle: CGFloat = 1.6
@IBInspectable var clockwise: Bool = true
override func draw(_ rect: CGRect) {
centreArcPerpendicular()
}
/**
This draws the self.text around an arc of radius r,
with the text centred at polar angle theta
*/
func centreArcPerpendicular() {
guard let context = UIGraphicsGetCurrentContext() else { return }
let string = text ?? ""
let size = bounds.size
context.translateBy(x: size.width / 2, y: size.height / 2)
let radius = getRadiusForLabel()
let l = string.count
let attributes = [NSAttributedStringKey.font : self.font!]
let characters: [String] = string.map { String($0) } // An array of single character strings, each character in str
var arcs: [CGFloat] = [] // This will be the arcs subtended by each character
var totalArc: CGFloat = 0 // ... and the total arc subtended by the string
// Calculate the arc subtended by each letter and their total
for i in 0 ..< l {
arcs += [chordToArc(characters[i].size(withAttributes: attributes).width, radius: radius)]
totalArc += arcs[i]
}
// Are we writing clockwise (right way up at 12 o'clock, upside down at 6 o'clock)
// or anti-clockwise (right way up at 6 o'clock)?
let direction: CGFloat = clockwise ? -1 : 1
let slantCorrection = clockwise ? -CGFloat.pi/2 : CGFloat.pi/2
// The centre of the first character will then be at
// thetaI = theta - totalArc / 2 + arcs[0] / 2
// But we add the last term inside the loop
var thetaI = angle - direction * totalArc / 2
for i in 0 ..< l {
thetaI += direction * arcs[i] / 2
// Call centre with each character in turn.
// Remember to add +/-90º to the slantAngle otherwise
// the characters will "stack" round the arc rather than "text flow"
centre(text: characters[i], context: context, radius: radius, angle: thetaI, slantAngle: thetaI + slantCorrection)
// The centre of the next character will then be at
// thetaI = thetaI + arcs[i] / 2 + arcs[i + 1] / 2
// but again we leave the last term to the start of the next loop...
thetaI += direction * arcs[i] / 2
}
}
func chordToArc(_ chord: CGFloat, radius: CGFloat) -> CGFloat {
// *******************************************************
// Simple geometry
// *******************************************************
return 2 * asin(chord / (2 * radius))
}
/**
This draws the String str centred at the position
specified by the polar coordinates (r, theta)
i.e. the x= r * cos(theta) y= r * sin(theta)
and rotated by the angle slantAngle
*/
func centre(text str: String, context: CGContext, radius r:CGFloat, angle theta: CGFloat, slantAngle: CGFloat) {
// Set the text attributes
let attributes : [NSAttributedStringKey : Any] = [
NSAttributedStringKey.foregroundColor: textColor!,
NSAttributedStringKey.font: font!
]
// Save the context
context.saveGState()
// Move the origin to the centre of the text (negating the y-axis manually)
context.translateBy(x: r * cos(theta), y: -(r * sin(theta)))
// Rotate the coordinate system
context.rotate(by: -slantAngle)
// Calculate the width of the text
let offset = str.size(withAttributes: attributes)
// Move the origin by half the size of the text
context.translateBy(x: -offset.width / 2, y: -offset.height / 2) // Move the origin to the centre of the text (negating the y-axis manually)
// Draw the text
str.draw(at: CGPoint(x: 0, y: 0), withAttributes: attributes)
// Restore the context
context.restoreGState()
}
func getRadiusForLabel() -> CGFloat {
// Imagine the bounds of this label will have a circle inside it.
// The circle will be as big as the smallest width or height of this label.
// But we need to fit the size of the font on the circle so make the circle a little
// smaller so the text does not get drawn outside the bounds of the circle.
let smallestWidthOrHeight = min(bounds.size.height, bounds.size.width)
let heightOfFont = text?.size(withAttributes: [NSAttributedStringKey.font: self.font]).height ?? 0
// Dividing the smallestWidthOrHeight by 2 gives us the radius for the circle.
return (smallestWidthOrHeight/2) - heightOfFont + 5
}
}
答案 3 :(得分：1)
@IBDesignable对于Swift 2的循环路径上的UILabel
非常感谢@Grimxn和@ mark-moeykens的绝对杀手工作。我已经对Mark的工作做了一个小型的重构，所以我可以在一个没有花时间更新到Swift 3的项目中使用它。想要分享，因为之前的帖子非常有用。
自定义UILabel的Swift 2代码
import UIKit
@IBDesignable
class ArcUILabel: UILabel
{
// *******************************************************
// DEFINITIONS (Because I'm not brilliant and I'll forget most this tomorrow.)
// Radius: A straight line from the center to the circumference of a circle.
// Circumference: The distance around the edge (outer line) the circle.
// Arc: A part of the circumference of a circle. Like a length or section of the circumference.
// Theta: A label or name that represents an angle.
// Subtend: A letter has a width. If you put the letter on the circumference, the letter's width
// gives you an arc. So now that you have an arc (a length on the circumference) you can
// use that to get an angle. You get an angle when you draw a line from the center of the
// circle to each end point of your arc. So "subtend" means to get an angle from an arc.
// Chord: A line segment connecting two points on a curve. If you have an arc then there is a
// start point and an end point. If you draw a straight line from start point to end point
// then you have a "chord".
// sin: (Super simple/incomplete definition) Or "sine" takes an angle in degrees and gives you a number.
// asin: Or "asine" takes a number and gives you an angle in degrees. Opposite of sine.
// More complete definition: http://www.mathsisfun.com/sine-cosine-tangent.html
// cosine: Also takes an angle in degrees and gives you another number from using the two radiuses (radii).
// *******************************************************
@IBInspectable var angle: CGFloat = 1.6
@IBInspectable var clockwise: Bool = true
override func drawRect(rect: CGRect)
{
centreArcPerpendicular()
}
/**
This draws the self.text around an arc of radius r,
with the text centred at polar angle theta
*/
func centreArcPerpendicular() {
guard let context = UIGraphicsGetCurrentContext() else { return }
let str = self.text ?? ""
let size = self.bounds.size
CGContextTranslateCTM(context, size.width / 2, size.height / 2)
let radius = getRadiusForLabel()
let l = str.characters.count
let attributes: [String : AnyObject] = [NSFontAttributeName: self.font]
let characters: [String] = str.characters.map { String($0) } // An array of single character strings, each character in str
var arcs: [CGFloat] = [] // This will be the arcs subtended by each character
var totalArc: CGFloat = 0 // ... and the total arc subtended by the string
// Calculate the arc subtended by each letter and their total
for i in 0 ..< l {
arcs += [chordToArc(characters[i].sizeWithAttributes(attributes).width, radius: radius)]
totalArc += arcs[i]
}
// Are we writing clockwise (right way up at 12 o'clock, upside down at 6 o'clock)
// or anti-clockwise (right way up at 6 o'clock)?
let direction: CGFloat = clockwise ? -1 : 1
let slantCorrection = clockwise ? -CGFloat(M_PI_2) : CGFloat(M_PI_2)
// The centre of the first character will then be at
// thetaI = theta - totalArc / 2 + arcs[0] / 2
// But we add the last term inside the loop
var thetaI = angle - direction * totalArc / 2
for i in 0 ..< l {
thetaI += direction * arcs[i] / 2
// Call centre with each character in turn.
// Remember to add +/-90º to the slantAngle otherwise
// the characters will "stack" round the arc rather than "text flow"
centre(text: characters[i], context: context, radius: radius, angle: thetaI, slantAngle: thetaI + slantCorrection)
// The centre of the next character will then be at
// thetaI = thetaI + arcs[i] / 2 + arcs[i + 1] / 2
// but again we leave the last term to the start of the next loop...
thetaI += direction * arcs[i] / 2
}
}
func chordToArc(_ chord: CGFloat, radius: CGFloat) -> CGFloat {
// *******************************************************
// Simple geometry
// *******************************************************
return 2 * asin(chord / (2 * radius))
}
/**
This draws the String str centred at the position
specified by the polar coordinates (r, theta)
i.e. the x= r * cos(theta) y= r * sin(theta)
and rotated by the angle slantAngle
*/
func centre(text str: String, context: CGContext, radius r:CGFloat, angle theta: CGFloat, slantAngle: CGFloat) {
// Set the text attributes
let attributes = [NSForegroundColorAttributeName: self.textColor,
NSFontAttributeName: self.font] as [String : AnyObject]
// Save the context
CGContextSaveGState(context)
// Move the origin to the centre of the text (negating the y-axis manually)
CGContextTranslateCTM(context, r * cos(theta), -(r * sin(theta)))
// Rotate the coordinate system
CGContextRotateCTM(context, -slantAngle)
// Calculate the width of the text
let offset: CGSize = str.sizeWithAttributes(attributes)
// Move the origin by half the size of the text
CGContextTranslateCTM(context, -offset.width / 2, -offset.height / 2)
// Draw the text
let txtStr = NSString(string: str)
txtStr.drawAtPoint(CGPoint(x: 0, y: 0), withAttributes: attributes)
// Restore the context
CGContextRestoreGState(context)
}
func getRadiusForLabel() -> CGFloat {
// Imagine the bounds of this label will have a circle inside it.
// The circle will be as big as the smallest width or height of this label.
// But we need to fit the size of the font on the circle so make the circle a little
// smaller so the text does not get drawn outside the bounds of the circle.
let smallestWidthOrHeight = min(self.bounds.size.height, self.bounds.size.width)
let heightOfFont = self.text?.sizeWithAttributes([NSFontAttributeName: self.font]).height ?? 0
// Dividing the smallestWidthOrHeight by 2 gives us the radius for the circle.
return (smallestWidthOrHeight/2) - heightOfFont + 5
}
}
答案 4 :(得分：0)
基于Grimxm的代码的C＃版本：
private void CenterArcPerpendicular(string text, CGContext context, float radius, double angle, UIColor textColor, UIFont font, bool isClockwise) {
var characters = text.ToCharArray();
var arcs = new List<float>() { };
float totalArc = 0;
for (var i = 0; i < characters.Length; i++)
{
var character = new NSString(new string(new char[] { characters[i] }));
var charSize = character.StringSize(font);
var arc = ChordToArc((float)charSize.Width, radius);
arcs.Add(arc);
totalArc += arc;
}
var direction = isClockwise ? -1 : 1;
var slantCorrection = (float)(isClockwise ? -(Math.PI / 2) : (Math.PI / 2));
var thetaI = angle - (direction * (totalArc / 2));
for (var i = 0; i < characters.Length; i++)
{
var character = new NSString(new string(new char[] { characters[i] }));
thetaI += direction * arcs[i] / 2;
CenterText(character, context: context, radius: radius, angle: thetaI, textColor: textColor, font: font, slantAngle: thetaI + slantCorrection);
thetaI += direction * arcs[i] / 2;
}
}
private float ChordToArc(float chord, float radius) {
return (float)(2 * Math.Asin(chord / (2 * radius)));
}
private void CenterText(NSString text, CGContext context, float radius, double angle, UIColor textColor, UIFont font, double slantAngle)
{
var attributes = new UIStringAttributes { Font = font, ForegroundColor = textColor };
context.SaveState();
context.ScaleCTM(1, -1);
var dX = radius * Math.Cos(angle);
var dY = -(radius * Math.Sin(angle));
context.TranslateCTM((nfloat)dX, (nfloat)dY);
context.RotateCTM(-(nfloat)slantAngle);
var offset = text.StringSize(font);
context.TranslateCTM(-offset.Width / 2, -offset.Height / 2);
text.DrawString(CGPoint.Empty, attributes);
context.RestoreState();
}
用于Xamarin iOS应用。
相关问题
最新问题
- 我写了这段代码，但我无法理解我的错误
- 我无法从一个代码实例的列表中删除 None 值，但我可以在另一个实例中。为什么它适用于一个细分市场而不适用于另一个细分市场？
- 是否有可能使 loadstring 不可能等于打印？卢阿
- java中的random.expovariate()
- Appscript 通过会议在 Google 日历中发送电子邮件和创建活动
- 为什么我的 Onclick 箭头功能在 React 中不起作用？
- 在此代码中是否有使用“this”的替代方法？
- 在 SQL Server 和 PostgreSQL 上查询，我如何从第一个表获得第二个表的可视化
- 每千个数字得到
- 更新了城市边界 KML 文件的来源？