ios - 如何捕捉可访问性焦点的变化？

Question

我想捕捉可访问性焦点的变化。

我搜索并尝试了 accessibilityElementDidBecomeFocused 但在光标更改后没有触发。我想为按钮添加值，并在光标更改后删除该值。

我的代码是这样的:

override func viewDidLoad() {
    flashButton.accessibilityLabel = "Change the flash status"
    flashButton.accessibilityTraits = [.button]
    flashButton.accessibilityIdentifier = "flashButton"
}

@IBAction func flashButtonTapped(_ sender: Any) {
    var currentFlashStatus = "off"
    guard let device =  AVCaptureDevice.default(AVCaptureDevice.DeviceType.builtInWideAngleCamera, for: AVMediaType.video, position: .back) else { return }
    guard device.hasTorch else { return }
    do {
        try device.lockForConfiguration()
        if device.torchMode == .on {
            device.torchMode = .off
            flashButton.image = UIImage(named: "flashOffIcon")
            currentFlashStatus = "off"
        } else {
            do {
                try device.setTorchModeOn(level: 1.0)
                flashButton.image = UIImage(named: "flashOnIcon")
                currentFlashStatus = "on"
            } catch {
                print(error)
            }
        }
        device.unlockForConfiguration()
    } catch {
        print(error)
    }
    flashButton.accessibilityLabel = "Turned \(currentFlashStatus) the flash"
}

首先，它会显示“更改闪光灯状态”，如果我双击它会显示“打开闪光灯状态”，这是正确的。

如果我更改光标并返回到闪光灯按钮，它应该说再次更改闪光灯状态。但是它说“打开闪光灯状态”

我怎样才能做到这一点？

Answer 1

I searched and tried accessibilityElementDidBecomeFocused but didn't trigger after cursor changed.

如果你想使用 UIAccessibilityFocus 非正式协议(protocol)方法，你必须直接在你的对象中覆盖它们，而不是在 View Controller 中(参见this answer)。创建 UIButton 的子类，例如:

import UIKit

class FlashButton: UIButton {}

extension FlashButton {

    override open func accessibilityElementDidBecomeFocused() {
    // Actions to be done when the element did become focused.
    }
}

If I change the cursor and come back to the flash button, it should say change the flash status again.

无论您选择闪光按钮多少次，在说更改其值之前，始终应先读出所需的状态。

下面的代码中提供了一个示例:

class FlashButton: UIButton {

    private var intStatus: Bool = false
    private var a11yLabelStatus: String = "off"

    var status: Bool {
        get { return intStatus }
        set(newValue) { intStatus = newValue }
    }
}

extension FlashButton {

    override open func accessibilityElementDidBecomeFocused() {
    // Actions to be done when the element did become focused.
    }

    override open func accessibilityElementDidLoseFocus() {
    // Actions to be done when the element did lose focus.
    }

    //This native a11y function replaces your defined IBAction to change and read out the flash status.
    override func accessibilityActivate() -> Bool {

        intStatus = (intStatus == true) ? false : true
        a11yLabelStatus = (intStatus == true) ? "on" : "off"

        UIAccessibility.post(notification: .announcement,
                             argument: "flash status is " + a11yLabelStatus)
        return true
    }

    override var accessibilityLabel: String? {
        get { return "the flash status is " + a11yLabelStatus }
        set { }
    }

    override var accessibilityHint: String? {
        get { return "double tap to change the value." }
        set { }
    }
}

How can I achieve this?

要么尝试使用 UIAccessibilityFocus 非正式协议(protocol)来捕捉焦点变化，要么只使用上面的代码片段来更改可访问性元素的状态:您可以结合两者，您可以根据自己的编码环境调整这些概念。 ;o)

还不够看this site致力于 a11y 开发人员，其中提供了代码片段和插图，可以为您的实现找到另一种解决方案。