Animate a Change in Part of an Nsmutableattributedstring

Animate a change in part of an NSMutableAttributedString

I achieved what I wanted to by getting the frames for the actual parentheses and creating new UILabels on top of my UITextView and animating those labels.

    @IBAction func didPressClosingParentheses(sender: AnyObject) {

    inputTextView.text = inputTextView.text + ")"
    var count = 1
    let currentString = inputTextView.attributedText.string
    let characterArray = Array(currentString)
    let closingIndex = characterArray.count - 1
    for i in reverse(0...closingIndex-1) {
        if characterArray[i] == "(" {
            count--
        }
        else if characterArray[i] == ")" {
            count++
        }
        if count == 0 {
            let startingIndex = i

            let openingRange = NSMakeRange(startingIndex, 1)
            let closingRange = NSMakeRange(closingIndex, 1)

            var openingFrame = inputTextView.layoutManager.boundingRectForGlyphRange(openingRange, inTextContainer: inputTextView.textContainer)

            openingFrame.origin.y += inputTextView.textContainerInset.top
            var openingLabel = UILabel(frame: openingFrame)
            openingLabel.text = "("
            openingLabel.font = UIFont(name: "HelveticaNeue-Thin", size: 28)
            openingLabel.textColor = whiteishColor
            openingLabel.backgroundColor = bluishColor

            var closingFrame = inputTextView.layoutManager.boundingRectForGlyphRange(closingRange, inTextContainer: inputTextView.textContainer)
            closingFrame.origin.y += inputTextView.textContainerInset.top
            var closingLabel = UILabel(frame: closingFrame)
            closingLabel.text = ")"
            closingLabel.font = UIFont(name: "HelveticaNeue-Thin", size: 28)
            closingLabel.textColor = whiteishColor
            closingLabel.backgroundColor = bluishColor

            inputTextView.addSubview(openingLabel)
            inputTextView.addSubview(closingLabel)

            UIView.animateWithDuration(0.4, delay: 0, usingSpringWithDamping: 0.7, initialSpringVelocity: 0.8, options: nil, animations: {
                openingLabel.transform = CGAffineTransformMakeScale(1.25, 1.25)
                closingLabel.transform = CGAffineTransformMakeScale(1.25, 1.25)

                }, nil)

            UIView.animateWithDuration(0.4, delay: 0.2, usingSpringWithDamping: 0.7, initialSpringVelocity: 0.8, options: nil, animations: {
                openingLabel.transform = CGAffineTransformMakeScale(1.0, 1.0)
                closingLabel.transform = CGAffineTransformMakeScale(1.0, 1.0)

                }, nil)
            UIView.animateWithDuration(0.25, delay: 0.4, options: nil, animations: {
                openingLabel.alpha = 0
                closingLabel.alpha = 0

                }, completion: { finished in
                    openingLabel.removeFromSuperview()
                    closingLabel.removeFromSuperview()
            })

            break
        }
    }

}

How to animate NSAttributedString?

If you need to animate a property that is not animatable, you can use CADisplayLink. That allows you to create your own animation by executing a method every time the screen refreshes. Although it looks sort of low-level, it is not really difficult to implement it.
You can find tutorials/examples on the web easily.

Note: It does not trigger your method periodically, therefore do not assume anything about timing and keep a counter and calculate progress your animation by yourself. Apart from that, CADisplayLink is cool.

Edit: As Max pointed out, CADisplayLink is not available for Mac. But there is CVDisplayLink, I guess you can achieve the desired animation by that. For more info on CVDisplayLink, you can have a look at that answer by Brad Larson.

Change attributes of multiple parts of a NSMutableAttributedString

Searching for start-end characters or character sequences is ok if you are certain they will never appear in resultX strings...

One approach would be to build a string piece by piece and create an array of ranges on the fly. At the end you simply slap the attributes on them.

NSMutableString *mTextToDraw = [[NSMutableString alloc] init];
NSMutableArray *mRangesToMod = [[NSMutableArray alloc] init];
NSValue *mRange = nil;

[mTextToDraw appendFormat:@"Summary of currently worked on process\n\nTitle name:\nResults for Process\n    "];

mRange = [NSValue valueWithRange:NSMakeRange(mTextToDraw.length,resultOne.length)];;
[mRangesToMod addObject: mRange];
[mString appendFormat:@"%@\n",resultOne];

mRange = [NSValue valueWithRange:NSMakeRange(mTextToDraw.length,resultTwo.length)];;
[mRangesToMod addObject: mRange];
[mString appendFormat:@"%@\n",resultTwo];

mRange = [NSValue valueWithRange:NSMakeRange(mTextToDraw.length,resultThree.length)];;
[mRangesToMod addObject: mRange];
[mString appendFormat:@"%@\n",resultThree];

NSMutableAttributedString *summaryBody = [[NSMutableAttributedString alloc] initWithString:mTextToDraw];

for (NSValue *vRange in mRangesToMod)
{
    NSRange range = vRange.rangeValue;

    [summaryBody setAttributes:@{NSFontAttributeName:[UIFont fontWithName:@"Roboto-Light" size:smallFont]}
                         range:range];

    // or you can use addAttribute...
}

I used "Roboto-Light" in my app - it won't work in yours as is. Just as an example. For test just put there some font other then the basic (original) one...

Is is possible to animate text color changing only in a part of text in iOS?

You can quite easily achieve this using CoreAnimation possibilities.
I've added a simple demo, you play with it here (just build the project and tap anywhere to see the animation).

The logic is the following:

1. Create a custom subclass of UIView.
2. When some text is set, create two similar CATextLayers, each with the same text and frame.
3. Set different foregroundColor and mask for those layers. The mask of the left layer will be the left part of the view, and the mask of the right layer will be the right part.
4. Animate foregroundColor for those layers (simultaneously).

The code of a custom view:

class CustomTextLabel: UIView {
    override init(frame: CGRect) {
        super.init(frame: frame)
        backgroundColor = .green
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    private var textLayer1: CATextLayer?
    private var textLayer2: CATextLayer?

    func setText(_ text: String, fontSize: CGFloat) {
        // create 2 layers with the same text and size, we'll set the colors for them later
        textLayer1 = createTextLayer(text, fontSize: fontSize)
        textLayer2 = createTextLayer(text, fontSize: fontSize)

        // estimate the frame size needed for the text layer with such text and font size
        let textSize = textLayer1!.preferredFrameSize()
        let w = frame.width, h = frame.height

        // calculate the frame such that both layers will be in center of view
        let centeredTextFrame = CGRect(x: (w-textSize.width)/2, y: (h-textSize.height)/2, width: textSize.width, height: textSize.height)
        textLayer1!.frame = centeredTextFrame
        textLayer2!.frame = centeredTextFrame

        // set up default color for the text
        textLayer1!.foregroundColor = UIColor.yellow.cgColor
        textLayer2!.foregroundColor = UIColor.yellow.cgColor

        // set background transparent, that's very important
        textLayer1!.backgroundColor = UIColor.clear.cgColor
        textLayer2!.backgroundColor = UIColor.clear.cgColor

        // set up masks, such that each layer's text is visible only in its part
        textLayer1!.mask = createMaskLayer(CGRect(x: 0, y: 0, width: textSize.width/2, height: textSize.height))
        textLayer2!.mask = createMaskLayer(CGRect(x: textSize.width/2, y: 0, width: textSize.width/2, height: textSize.height))

        layer.addSublayer(textLayer1!)
        layer.addSublayer(textLayer2!)
    }

    private var finishColor1: UIColor = .black, finishColor2: UIColor = .black
    func animateText(leftPartColor1: UIColor, leftPartColor2: UIColor, rightPartColor1: UIColor, rightPartColor2: UIColor) {
        finishColor1 = leftPartColor2
        finishColor2 = rightPartColor2

        if let layer1 = textLayer1, let layer2 = textLayer2 {
            CATransaction.begin()
            let animation1 = CABasicAnimation(keyPath: "foregroundColor")
            animation1.fromValue = leftPartColor1.cgColor
            animation1.toValue = leftPartColor2.cgColor
            animation1.duration = 3.0
            layer1.add(animation1, forKey: "animation1")

            let animation2 = CABasicAnimation(keyPath: "foregroundColor")
            animation2.fromValue = rightPartColor1.cgColor
            animation2.toValue = rightPartColor2.cgColor
            animation2.duration = 3.0
            layer2.add(animation2, forKey: "animation2")

            CATransaction.setCompletionBlock {
                self.textLayer1?.foregroundColor = self.finishColor1.cgColor
                self.textLayer2?.foregroundColor = self.finishColor2.cgColor
            }

            CATransaction.commit()
        }
    }

    private func createTextLayer(_ text: String, fontSize: CGFloat) -> CATextLayer {
        let textLayer = CATextLayer()
        textLayer.string = text
        textLayer.fontSize = fontSize // TODO: also set font name
        textLayer.contentsScale = UIScreen.main.scale

        return textLayer
    }

    private func createMaskLayer(_ holeRect: CGRect) -> CAShapeLayer {
        let layer = CAShapeLayer()

        let path = CGMutablePath()

        path.addRect(holeRect)
        path.addRect(bounds)

        layer.path = path
        layer.fillRule = CAShapeLayerFillRule.evenOdd
        layer.opacity = 1

        return layer
    }
}

The calls of a custom view:

class ViewController: UIViewController {

    var customLabel: CustomTextLabel!
    override func viewDidLoad() {
        super.viewDidLoad()

        let viewW = view.frame.width, viewH = view.frame.height
        let labelW: CGFloat = 200, labelH: CGFloat = 50

        customLabel = CustomTextLabel(frame: CGRect(x: (viewW-labelW)/2, y: (viewH-labelH)/2, width: labelW, height: labelH))
        customLabel.setText("Optimizing...", fontSize: 20)
        view.addSubview(customLabel)

        let tapRecogniner = UITapGestureRecognizer(target: self, action: #selector(onTap))
        view.addGestureRecognizer(tapRecogniner)
    }

    @objc func onTap() {
        customLabel.animateText(leftPartColor1: UIColor.blue,
                                leftPartColor2: UIColor.red,
                                rightPartColor1: UIColor.white,
                                rightPartColor2: UIColor.black)
    }

}

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