I have a UITextView in my app which is updated as the user types. But when I start typing in the UITextView, the cursor starts to flicker and move up and down quickly. How can I fix this bug?
This is how the UITextView is update-
A Cocoa Touch Class file called Highlighter.swift-
import Foundation
import UIKit
// text hightlighter
class SyntaxGroup {
var wordCollection : [String]
var type : String
var color : UIColor
init(wordCollection_I : [String], type_I : String, color_I: UIColor) {
wordCollection = wordCollection_I
type = type_I
color = color_I
}
}
class SyntaxDictionairy {
var collections : [SyntaxGroup] = []
}
class SyntaxRange {
var range : NSRange
var color : UIColor
init (color_I : UIColor, range_I : NSRange) {
color = color_I
range = range_I
}
}
class HighLighter {
private var ranges : [SyntaxRange] = []
var highlightedString : NSMutableAttributedString = NSMutableAttributedString()
var syntaxDictionairy : SyntaxDictionairy
init (syntaxDictionairy_I : SyntaxDictionairy) {
syntaxDictionairy = syntaxDictionairy_I
}
func run(string : String?, completion: (finished: Bool) -> Void) {
ranges = []
highlightedString = NSMutableAttributedString()
var baseString = NSMutableString()
let qualityOfServiceClass = QOS_CLASS_DEFAULT
let backgroundQueue = dispatch_get_global_queue(qualityOfServiceClass, 0)
dispatch_async(backgroundQueue) { () -> Void in
if string != nil && string != "" {
self.highlightedString = NSMutableAttributedString(string: string!)
for i in 0..<self.syntaxDictionairy.collections.count {
for iB in 0..<self.syntaxDictionairy.collections[i].wordCollection.count {
let currentWordToCheck = self.syntaxDictionairy.collections[i].wordCollection[iB]
baseString = NSMutableString(string: string!)
while baseString.containsString(self.syntaxDictionairy.collections[i].wordCollection[iB]) {
let nsRange = (baseString as NSString).rangeOfString(currentWordToCheck)
let newSyntaxRange = SyntaxRange(color_I: self.syntaxDictionairy.collections[i].color, range_I: nsRange)
self.ranges.append(newSyntaxRange)
var replaceString = ""
for _ in 0..<nsRange.length {
replaceString += "§" // secret unallowed character
}
baseString.replaceCharactersInRange(nsRange, withString: replaceString)
}
}
}
for i in 0..<self.ranges.count {
self.highlightedString.addAttribute(NSForegroundColorAttributeName, value: self.ranges[i].color, range: self.ranges[i].range)
}
}
dispatch_sync(dispatch_get_main_queue()) { () -> Void in
completion(finished: true)
}
}
}
}
This is the code in the ViewController.swift file-
import UIKit
class ViewController: UIViewController, UITextViewDelegate {
@IBOutlet weak var myTextView: UITextView!
var syntaxHighLighter : HighLighter!
override func viewDidLoad() {
super.viewDidLoad()
setUpHighLighter()
myTextView.delegate = self
}
func setUpHighLighter() {
// build a dict of words to highlight
let redColor = UIColor(red: 0.5, green: 0.0, blue: 0.0, alpha: 1.0)
let blueColor = UIColor(red: 0.0, green: 0.0, blue: 0.5, alpha: 1.0)
let greenColor = UIColor(red: 0.0, green: 0.5, blue: 0.0, alpha: 1.0)
let redGroup = SyntaxGroup(wordCollection_I: ["red","bordeaux"], type_I: "Color", color_I: redColor)
let blueGroup = SyntaxGroup(wordCollection_I: ["coralblue","blue","skyblue","azur"], type_I: "Color", color_I: blueColor)
let greenGroup = SyntaxGroup(wordCollection_I: ["green"], type_I: "Color", color_I: greenColor)
let dictionairy : SyntaxDictionairy = SyntaxDictionairy()
dictionairy.collections.append(blueGroup)
dictionairy.collections.append(greenGroup)
dictionairy.collections.append(redGroup)
syntaxHighLighter = HighLighter(syntaxDictionairy_I: dictionairy)
}
func textViewDidChange(textView: UITextView) {
let currentRange = myTextView.selectedRange
syntaxHighLighter.run(myTextView.text) { (finished) -> Void in
self.myTextView.attributedText = self.syntaxHighLighter.highlightedString
self.myTextView.selectedRange = currentRange
}
}
}
Check that you are running the latest OS and Xcode.
Try this to figure out when it is jumping:
You could again use a bool to check if the selection change is because of the reset after highlighting or not. If it is not you can use a breakpoint to see what is going on.
func textViewDidChangeSelection(textView: UITextView) {
print("selection changed: \(myTextView.selectedTextRange!)")
}
This could help: a check too see if the length of the textview is still equal to the length of the highlighted string.
func textViewDidChange(textView: UITextView) {
let currentRange = myTextView.selectedRange
syntaxHighLighter.run(myTextView.text) { (finished) -> Void in
// if the highlighter was slower than typing, ABORT
guard let textInUITextView = self.myTextfield.attributedText where textInUITextView.length == self.syntaxHighLighter.highlightedString.length else {
return
}
self.myTextView.attributedText = self.syntaxHighLighter.highlightedString
self.myTextView.selectedRange = currentRange
}
}
This could help: it will prevent the highlighter from running more than once.
class HighLighter {
private var ranges : [SyntaxRange] = []
var highlightedString : NSMutableAttributedString = NSMutableAttributedString()
var syntaxDictionairy : SyntaxDictionairy
private var running : Bool = false
init (syntaxDictionairy_I : SyntaxDictionairy) {
syntaxDictionairy = syntaxDictionairy_I
}
func run(string : String?, completion: (finished: Bool) -> Void) {
if running == true {
print("double action")
return
}
running = true
ranges = []
highlightedString = NSMutableAttributedString()
var baseString = NSMutableString()
let qualityOfServiceClass = QOS_CLASS_DEFAULT
let backgroundQueue = dispatch_get_global_queue(qualityOfServiceClass, 0)
dispatch_async(backgroundQueue) { () -> Void in
if string != nil && string != "" {
self.highlightedString = NSMutableAttributedString(string: string!)
for i in 0..<self.syntaxDictionairy.collections.count {
for iB in 0..<self.syntaxDictionairy.collections[i].wordCollection.count {
let currentWordToCheck = self.syntaxDictionairy.collections[i].wordCollection[iB]
baseString = NSMutableString(string: string!)
while baseString.containsString(self.syntaxDictionairy.collections[i].wordCollection[iB]) {
let nsRange = (baseString as NSString).rangeOfString(currentWordToCheck)
let newSyntaxRange = SyntaxRange(color_I: self.syntaxDictionairy.collections[i].color, range_I: nsRange)
self.ranges.append(newSyntaxRange)
var replaceString = ""
for _ in 0..<nsRange.length {
replaceString += "§" // secret unallowed character
}
baseString.replaceCharactersInRange(nsRange, withString: replaceString)
}
}
}
for i in 0..<self.ranges.count {
self.highlightedString.addAttribute(NSForegroundColorAttributeName, value: self.ranges[i].color, range: self.ranges[i].range)
}
}
dispatch_sync(dispatch_get_main_queue()) { () -> Void in
self.running = false
completion(finished: true)
}
}
}
}