【发布时间】：2020-08-19 02:08:40
【问题描述】：
我正在构建一个 PDF 文档，并且图像和文本正在作为 CALayers 写入视图。我需要在 CATextLayer 的边框内垂直居中我的文本。我正在使用我在 2016 年找到的一个类，如下所示，它覆盖了 draw 函数。我想知道是否有任何新技巧可以使这项工作发挥作用？
正如您在运行此代码时看到的那样，单元格 2 的文本甚至没有显示，单元格 3 的文本也没有垂直居中。
非常感谢任何可以帮助我的人。
//
// ViewController.swift
// CALayers Example
//
// Created by Thomas Carroll on 8/18/20.
// Copyright © 2020 Thomas Carroll. All rights reserved.
//
import Cocoa
class ViewController: NSViewController {
let myLayers = MyLayers()
override func viewDidLoad() {
super.viewDidLoad()
self.view.wantsLayer = true
self.view.layer?.addSublayer(myLayers.insertGrid())
self.view.layer?.addSublayer(myLayers.insertText())
// Do any additional setup after loading the view.
}
override var representedObject: Any? {
didSet {
// Update the view, if already loaded.
}
}
}
//
// MyLayers.swift
// CALayers Example
//
// Created by Thomas Carroll on 8/18/20.
// Copyright © 2020 Thomas Carroll. All rights reserved.
//
import Cocoa
// Set up constant variables
let pageWidth:Float = 72*8.5
let pageHeight:Float = 72*11
// Set up coordinates
let leftX = Int(pageWidth/2-72*2.5)
let col1X = Int(leftX+72)
let col2X = Int(col1X+72)
let col3X = Int(col2X+72)
let col4X = Int(col3X+72)
let rightX = Int(col4X+72)
let bottomY = Int(pageHeight/2-72*2.5)
let row4Y = Int(bottomY+72)
let row3Y = Int(row4Y+72)
let row2Y = Int(row3Y+72)
let row1Y = Int(row2Y+72)
let topY = Int(row1Y+72)
// Set the extension to draw Bezier paths into a CAShapeLayer
extension NSBezierPath {
// Credit - Henrick - 9/18/2016
// https://stackoverflow.com/questions/1815568/how-can-i-convert-nsbezierpath-to-cgpath
public var cgPath: CGPath {
let path = CGMutablePath()
var points = [CGPoint](repeating: .zero, count: 3)
for i in 0 ..< self.elementCount {
let type = self.element(at: i, associatedPoints: &points)
switch type {
case .moveTo:
path.move(to: points[0])
case .lineTo:
path.addLine(to: points[0])
case .curveTo:
path.addCurve(to: points[2], control1: points[0], control2: points[1])
case .closePath:
path.closeSubpath()
@unknown default:
print("Error occured in NSBezierPath extension.")
}
}
return path
}
}
class MyLayers {
class VerticallyAlignedTextLayer : CATextLayer {
func calculateMaxLines() -> Int {
let maxSize = CGSize(width: frame.size.width, height: frame.size.height)
let font = NSFont(descriptor: self.font!.fontDescriptor, size: self.fontSize)
let charSize = (font?.capHeight)!
let text = (self.string ?? "") as! NSString
let textSize = text.boundingRect(with: maxSize, options: .usesLineFragmentOrigin, attributes: [NSAttributedString.Key.font: font!], context: nil)
let linesRoundedUp = Int(ceil(textSize.height/charSize))
return linesRoundedUp
}
override func draw(in context: CGContext) {
let height = self.bounds.size.height
let fontSize = self.fontSize
let lines = CGFloat(calculateMaxLines())
let yDiff = (height - lines * fontSize) / 2 - lines * fontSize / 10
context.saveGState()
context.translateBy(x: 0, y: yDiff) // Use -yDiff when in non-flipped coordinates (like macOS's default)
super.draw(in: context)
context.restoreGState()
}
}
func insertGrid() -> CALayer {
/*
Draws a single table grid of 25 boxes (5 high by 5 wide)
centered on a letter sized page
*/
// Create a new shape layer for the grid
let gridLayer = CAShapeLayer()
// Create the path
let gridPath = NSBezierPath()
// Assign the grid fill and stroke colors
gridLayer.strokeColor = NSColor.purple.cgColor
gridLayer.fillColor = NSColor.clear.cgColor
// Draw the paths for the grid
// Create the outside box
gridPath.move(to: CGPoint(x: leftX, y: bottomY)) // Bottom left corner
gridPath.line(to: CGPoint(x: leftX, y: topY)) // Column 1, left line
gridPath.line(to: CGPoint(x: rightX, y: topY)) // Row 1, top line
gridPath.line(to: CGPoint(x: rightX, y: bottomY)) // Column 5 right line
gridPath.line(to: CGPoint(x: leftX, y: bottomY)) // Row 5 bottom line
// Add in column lines
gridPath.move(to: CGPoint(x: col1X, y: topY)) // Between columns 1 & 2
gridPath.line(to: CGPoint(x: col1X, y: bottomY)) // Line between columns 1 & 2
gridPath.move(to: CGPoint(x: col2X, y: topY)) // Between columns 2 & 3
gridPath.line(to: CGPoint(x: col2X, y: bottomY)) // Line between columns 2 & 3
gridPath.move(to: CGPoint(x: col3X, y: topY)) // Between columns 3 & 4
gridPath.line(to: CGPoint(x: col3X, y: bottomY)) // Line between columns 3 & 4
gridPath.move(to: CGPoint(x: col4X, y: topY)) // Between columns 4 & 5
gridPath.line(to: CGPoint(x: col4X, y: bottomY)) // Line between columns 4 & 5
// Add in row lines
gridPath.move(to: CGPoint(x: leftX, y: row1Y)) // Between rows 1 & 2
gridPath.line(to: CGPoint(x: rightX, y: row1Y)) // Line between rows 1 & 2
gridPath.move(to: CGPoint(x: leftX, y: row2Y)) // Between rows 2 & 3
gridPath.line(to: CGPoint(x: rightX, y: row2Y)) // Line between rows 2 & 3
gridPath.move(to: CGPoint(x: leftX, y: row3Y)) // Between rows 3 & 4
gridPath.line(to: CGPoint(x: rightX, y: row3Y)) // Line between rows 3 & 4
gridPath.move(to: CGPoint(x: leftX, y: row4Y)) // Between rows 4 & 5
gridPath.line(to: CGPoint(x: rightX, y: row4Y)) // Line between rows 4 & 5
// Close the path
gridPath.close()
// Add grid to layer (note the use of the cgPath extension)
gridLayer.path = gridPath.cgPath
return gridLayer
}
func insertText() -> CALayer {
// Create a CALayer to add the textLayer to
let myCALayer = CALayer()
// Set up an array to hold the x coordinate for each column
let colPosX = [leftX, col1X, col2X, col3X, col4X]
// Set up an array to hold the y coordinate for the first card
let rowPosY = [row1Y, row2Y, row3Y, row4Y, bottomY]
// Set some default text to be used in the textLayers
let cellText = ["This is some cell 1 text", "Cell 2 text", "This is text cell 3"]
for i in (0...2) {
let textLayer = VerticallyAlignedTextLayer()
textLayer.string = cellText[i]
textLayer.fontSize = 14
// Set the frame to be 1 pixel smaller than the grid cell to provide 1px padding
textLayer.frame = CGRect(origin: CGPoint(x: Int(colPosX[i])+1, y: Int(rowPosY[i])+1), size: CGSize(width: 70, height: 70))
textLayer.alignmentMode = .center
textLayer.isWrapped = true
textLayer.foregroundColor = NSColor.black.cgColor
textLayer.backgroundColor = NSColor.clear.cgColor
textLayer.truncationMode = .none
myCALayer.addSublayer(textLayer)
}
return myCALayer
}
}
【问题讨论】：
-
如果我将“单元格 2 文本”更改为“某些单元格 2 文本”单元格 2 然后显示文本。
-
复杂代码；如果您想查看原始文本，请尝试将 YDiff 设为负值。当它是一个大的正值时，文本不会正确转置。
-
我改变了它，但仍然没有任何区别。