How can I blur a UITextView so the text appears blurred?

How to Blur UITextView Text in Swift

Learn how to apply a blur effect to the text within a UITextView in iOS using UIVisualEffectView, creating a visually appealing and dynamic user interface.

Blurring text within a UITextView can add a sophisticated touch to your iOS application's UI, allowing you to obscure sensitive information or create artistic effects. While UIVisualEffectView is commonly used for blurring backgrounds, applying it directly to the text of a UITextView requires a slightly different approach. This article will guide you through the process of achieving a text-blurring effect using modern UIKit techniques in Swift.

Understanding the Challenge

A UITextView is essentially a UIScrollView subclass that hosts a UITextInput compliant view for text rendering. Applying a UIVisualEffectView directly as a subview to a UITextView would blur the entire view, including its background and frame, but not selectively the text content itself against a transparent background. To blur only the text, we need to ensure the blur effect is applied over the text, effectively obscuring it, while the UITextView itself remains clear or has its own styling. The key is to position the blur view correctly relative to the text content.

Implementing the Blur Effect

The most effective way to blur the text within a UITextView is to place a UIVisualEffectView directly on top of the UITextView's text content, matching its frame and ensuring it's always above the text. This involves creating a UIBlurEffect and wrapping it in a UIVisualEffectView. We'll then add this blur view as a subview to the UITextView and manage its layout, especially when the text view's content or frame changes.

import UIKit

class BlurTextView: UITextView {

    private var blurEffectView: UIVisualEffectView?

    var isTextBlurred: Bool = false {
        didSet {
            updateBlurEffect()
        }
    }

    override init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)
        setupBlurEffectView()
    }

    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setupBlurEffectView()
    }

    private func setupBlurEffectView() {
        let blurEffect = UIBlurEffect(style: .light)
        blurEffectView = UIVisualEffectView(effect: blurEffect)
        blurEffectView?.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        blurEffectView?.isUserInteractionEnabled = false // Allow interaction with the text view underneath
        
        if let blurView = blurEffectView {
            addSubview(blurView)
            bringSubviewToFront(blurView) // Ensure blur is on top
        }
        updateBlurEffect()
    }

    private func updateBlurEffect() {
        blurEffectView?.isHidden = !isTextBlurred
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        // Ensure the blur effect view always matches the text view's bounds
        blurEffectView?.frame = bounds
    }
    
    // Optional: Add a method to toggle blur from outside
    func toggleBlur() {
        isTextBlurred.toggle()
    }
}

A custom UITextView subclass that applies a blur effect over its text content.

Integrating the Custom TextView

Once you have the BlurTextView class, you can integrate it into your UIViewController just like any other UITextView. You can instantiate it programmatically or via a Storyboard/XIB. The isTextBlurred property allows you to easily toggle the blur effect on and off, which is useful for scenarios like revealing text upon user interaction or permission.

import UIKit

class ViewController: UIViewController {

    private var blurredTextView: BlurTextView! // Use your custom class
    private var toggleButton: UIButton!

    override func viewDidLoad() {
        super.viewDidLoad()
        setupBlurredTextView()
        setupToggleButton()
    }

    private func setupBlurredTextView() {
        blurredTextView = BlurTextView()
        blurredTextView.translatesAutoresizingMaskIntoConstraints = false
        blurredTextView.text = "This is some example text that will be blurred. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua."
        blurredTextView.font = UIFont.systemFont(ofSize: 18)
        blurredTextView.textColor = .black
        blurredTextView.backgroundColor = .white
        blurredTextView.layer.cornerRadius = 8
        blurredTextView.clipsToBounds = true
        blurredTextView.isEditable = false
        blurredTextView.isSelectable = false
        blurredTextView.isTextBlurred = true // Start with text blurred

        view.addSubview(blurredTextView)

        NSLayoutConstraint.activate([
            blurredTextView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 20),
            blurredTextView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20),
            blurredTextView.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20),
            blurredTextView.heightAnchor.constraint(equalToConstant: 200)
        ])
    }
    
    private func setupToggleButton() {
        toggleButton = UIButton(type: .system)
        toggleButton.translatesAutoresizingMaskIntoConstraints = false
        toggleButton.setTitle("Toggle Blur", for: .normal)
        toggleButton.addTarget(self, action: #selector(toggleBlurAction), for: .touchUpInside)
        
        view.addSubview(toggleButton)
        
        NSLayoutConstraint.activate([
            toggleButton.topAnchor.constraint(equalTo: blurredTextView.bottomAnchor, constant: 20),
            toggleButton.centerXAnchor.constraint(equalTo: view.centerXAnchor)
        ])
    }

    @objc private func toggleBlurAction() {
        blurredTextView.toggleBlur()
        let buttonTitle = blurredTextView.isTextBlurred ? "Show Text" : "Hide Text"
        toggleButton.setTitle(buttonTitle, for: .normal)
    }
}

Example ViewController demonstrating how to use the BlurTextView.

Screenshot of a UITextView with blurred text and a toggle button.

Considerations and Enhancements

When implementing this blur effect, keep the following in mind:

• Performance: UIVisualEffectView is highly optimized, but excessive use or complex animations involving many blur views can impact performance. For a single UITextView, it should be fine.
• User Interaction: By setting isUserInteractionEnabled = false on the blurEffectView, we ensure that touches pass through to the underlying UITextView, allowing for scrolling and other interactions.
• Dynamic Content: If the UITextView's content size changes frequently (e.g., as the user types), ensure the blurEffectView's frame is updated accordingly. Our layoutSubviews() override handles this for frame changes.
• Accessibility: As mentioned, provide alternatives for users with visual impairments. The blur might also be distracting for some users, so offering a way to disable it is good practice.
• Customization: You can experiment with different UIBlurEffect.Style values (e.g., .extraLight, .dark, .regular) to achieve various visual effects.

1. Step 1

Create a custom UITextView subclass, for example, BlurTextView.

2. Step 2

Inside the subclass, instantiate a UIVisualEffectView with a UIBlurEffect (e.g., .light style).

3. Step 3

Add the UIVisualEffectView as a subview to your BlurTextView instance.

4. Step 4

Set the blurEffectView.isUserInteractionEnabled property to false to allow interaction with the underlying text.

5. Step 5

Override layoutSubviews() in your custom BlurTextView to ensure the blurEffectView always matches the bounds of the UITextView.

6. Step 6

Add a public property (e.g., isTextBlurred) to control the visibility of the blur effect.

7. Step 7

Integrate your BlurTextView into your UIViewController and set its isTextBlurred property as needed.