アプリを視覚的にアクセシブルにする – WWDC2020

// Button Shapes
func observeButtonShapesNotification() {
    // Make buttons more visible by using shapes.
    // If your default design does not include button shapes, observe this notification to make visual changes.
    NotificationCenter.default.addObserver(self, selector: #selector(updateButtonShapes), name: UIAccessibility.buttonShapesEnabledStatusDidChangeNotification, object: nil)
}

@objc func updateButtonShapes() {
    if UIAccessibility.buttonShapesEnabled {
        // Use extra visualizations for buttons.
    } else {
        // Use default design for buttons.
    }
}

// Differentiate Without Color
func observeDifferentiateWithoutColorNotification() {
    // Use symbols or shapes to convey meaning instead of relying on color alone.
    // If your default design does not differentiate without color, observe this notification to make visual changes.
    NotificationCenter.default.addObserver(self, selector: #selector(updateColorAndSymbols), name: NSNotification.Name(UIAccessibility.differentiateWithoutColorDidChangeNotification), object: nil)
}

@objc func updateColorAndSymbols() {
    if UIAccessibility.shouldDifferentiateWithoutColor {
        // Use symbols or shapes to convey meaning.
    } else {
        // Use default design.
    }
}

// Smart Invert Colors
extension UIView {
    @available(iOS 11.0, tvOS 11.0)
    var accessibilityIgnoresInvertColors: Bool { get set }
}

// 大きなテキストの設定
// 画面上で表示が調整されると呼び出される
override func traitCollectionDidChange (_ previousTraitCollection: UITraitCollection?) {

     if (traitCollection.preferredContentSizeCategory       
         < .accessibilityMedium) { // Default font sizes

         stackView.axis = .horizontal
         stackView.alignment = .center

     } else { // Accessibility font sizes

         // ディスプレイの幅を最大限利用したラベル表示が可能
         stackView.axis = .vertical
         stackView.alignment = .leading

     }
}

// 太文字の設定
func observeBoldTextNotification() {
    // Update labels to use bold or heavy font styles.
    // If you aren't using system font styles, observe this notification to make visual changes.
    NotificationCenter.default.addObserver(self, selector: #selector(updateLabelWeight), name: UIAccessibility.boldTextStatusDidChangeNotification, object: nil)
}

@objc func updateLabelWeight() {
    if UIAccessibility.isBoldTextEnabled {
        // Use bold or heavy font weight
    } else {
        // Use font weight that is default to your design.
    }
}

// モーションエフェクトの抑制
func observeReduceMotionNotification() {
    // Observe this notification to reduce or remove the frequency and intensity of motion effects.
    NotificationCenter.default.addObserver(self, selector: #selector(updateMotionEffects), name: UIAccessibility.reduceMotionStatusDidChangeNotification, object: nil)
}

@objc func updateMotionEffects() {
    if UIAccessibility.isReduceMotionEnabled {
        // Reduce or remove extraneous motion effects.
    } else {
        // Use default motion effects.
    }
}

// Prefer cross fade transitionsの実装
func observeCrossFadeTransitionsNotification() {
    // Reduce or remove sliding animations for transitioning views.
    // If you aren't using system-provided navigation, observe this notification to make visual changes.
    NotificationCenter.default.addObserver(self, selector: #selector(updateTransitionEffects), name: UIAccessibility.prefersCrossFadeTransitionsStatusDidChange, object: nil)
}

@objc func updateTransitionEffects() {
    if UIAccessibility.prefersCrossFadeTransitions {
        // Replace sliding transitions with cross-fade animations.
    } else {
        // Use default sliding transitions.
    }
}

// Reduce Transparencyの設定通知実装
func observeReduceTransparencyNotification() {
    // Reduce or remove transparency by adjusting these effects to be completely opaque.
    // If you aren't using system-provided visual effects for blurs or vibrancy, observe this notification to make visual changes.
    NotificationCenter.default.addObserver(self, selector: #selector(updateTransparencyEffects), name: UIAccessibility.reduceTransparencyStatusDidChangeNotification, object: nil)
}

@objc func updateTransparencyEffects() {
    if UIAccessibility.isReduceTransparencyEnabled {
        // Make transparency effects opaque.
    } else {
        // Use default transparency.
    }
}