ios - 在 iOS 中请求相机权限对话框启动(主要权限)

Question

在确保最佳体验的同时提示用户提供对相机(或其他功能)的访问权限的最有效方法是什么？

访问相机时，iOS 必须征求客户许可才能允许访问。众所周知，如果客户说“不”但随后改变了主意，则无法从您的应用程序中撤销此决定。他们必须转到“设置”并按照一系列步骤重新启用访问权限，即:

设置 -> 隐私 -> 相机 -> [你的应用] -> 打开开关

Answer 1

Permission Priming 是一种有效的方法，可以避免您的客户可能拒绝访问您应用的关键功能。

在 iOS 上，应用程序仅允许针对每个功能触发一次默认系统权限。权限启动是指应用程序通过模拟系统权限的警报“启动”客户。

这样做的好处是，如果客户选择退出(选择取消)，应用程序仍然可以在以后再次询问，直到他们说是——此时显示实际的系统权限并且客户据统计，他们随后改变主意并进入负面工作流程的可能性较小。

此外，由于 cameraSelected() 执行此工作流程，如果用户拒绝，但随后在将来某个时间确实更改了他们的设置，应用程序将立即反射(reflect)新的权限而无需进一步输入(即用户可以切换到设置、更改权限，然后切换回应用程序)。

下面是一些Swift 3代码来实现这个特性:

[更新:包括一个解决方案，用于打开指向设置的深层链接，用户可以在其中启用摄像头访问权限(如果他们之前拒绝过)。]

[更新 2:添加了用于 Analytics 实现的示例行。]

func cameraSelected() {
    // First we check if the device has a camera (otherwise will crash in Simulator - also, some iPod touch models do not have a camera).
    if let deviceHasCamera = UIImagePickerController.isSourceTypeAvailable(.camera) {
        let authStatus = AVCaptureDevice.authorizationStatus(forMediaType: AVMediaTypeVideo)
        switch authStatus {
            case .authorized:
                showCameraPicker()
            case .denied:
                alertPromptToAllowCameraAccessViaSettings()
            case .notDetermined:
                permissionPrimeCameraAccess()
            default:
                permissionPrimeCameraAccess()
        }
    } else {
        let alertController = UIAlertController(title: "Error", message: "Device has no camera", preferredStyle: .alert)
        let defaultAction = UIAlertAction(title: "OK", style: .default, handler: { (alert) in
            Analytics.track(event: .permissionsPrimeCameraNoCamera)
        })
        alertController.addAction(defaultAction)
        present(alertController, animated: true, completion: nil)
    }
}


func alertPromptToAllowCameraAccessViaSettings() {
    let alert = UIAlertController(title: "\"<Your App>\" Would Like To Access the Camera", message: "Please grant permission to use the Camera so that you can  <customer benefit>.", preferredStyle: .alert )
    alert.addAction(UIAlertAction(title: "Open Settings", style: .cancel) { alert in
        Analytics.track(event: .permissionsPrimeCameraOpenSettings)
        if let appSettingsURL = NSURL(string: UIApplicationOpenSettingsURLString) {
          UIApplication.shared.openURL(appSettingsURL)
        }
    })
    present(alert, animated: true, completion: nil)
}


func permissionPrimeCameraAccess() {
    let alert = UIAlertController( title: "\"<Your App>\" Would Like To Access the Camera", message: "<Your App> would like to access your Camera so that you can <customer benefit>.", preferredStyle: .alert )
    let allowAction = UIAlertAction(title: "Allow", style: .default, handler: { (alert) -> Void in
        Analytics.track(event: .permissionsPrimeCameraAccepted)
        if AVCaptureDevice.devices(withMediaType: AVMediaTypeVideo).count > 0 {
            AVCaptureDevice.requestAccess(forMediaType: AVMediaTypeVideo, completionHandler: { [weak self] granted in
                DispatchQueue.main.async {
                    self?.cameraSelected() // try again
                }
            })
        }
    })
    alert.addAction(allowAction)
    let declineAction = UIAlertAction(title: "Not Now", style: .cancel) { (alert) in
        Analytics.track(event: .permissionsPrimeCameraCancelled)
    }
    alert.addAction(declineAction)
    present(alert, animated: true, completion: nil)
}


func showCameraPicker() {
    let picker = UIImagePickerController()
    picker.delegate = self
    picker.modalPresentationStyle = UIModalPresentationStyle.currentContext
    picker.allowsEditing = false
    picker.sourceType = UIImagePickerControllerSourceType.camera
    present(picker, animated: true, completion: nil)
}