Putting loading animation over VNDocumentViewController Swift - ios

Question

Is it possible to put a loading animation over the VNDocumentViewController? As in, when the user presses the Save button, is there a way for me to somehow indicate that the Vision is processing the image and hasn't frozen? Right now, in my app, there is a long pause between the user pressing Save and the actual image being processed.Here is an example from another post of what I'm trying to create

Answer 1

Here is one example of adding a loading indicator using UIActivityIndicatorView().
startAnimating() to start the animation and stopAnimation() to stop the animation.
iOS - Display a progress indicator at the center of the screen rather than the view
guard let topWindow = UIApplication.shared.windows.last else {return}
let overlayView = UIView(frame: topWindow.bounds)
overlayView.backgroundColor = UIColor.clear
topWindow.addSubview(overlayView)
let hudView = UIActivityIndicatorView()
hudView.bounds = CGRect(x: 0, y: 0, width: 20, height: 20)
overlayView.addSubview(hudView)
hudView.center = overlayView.center
hudView.startAnimating()
Alternatively, you could look into using Cocoapod MBProgressHud
https://cocoapods.org/pods/MBProgressHUD

Answer 2

There's a way you can extend a class in Swift that captures this problem well. The idea is you want a UIActivityIndicator in your VNDocumentCameraViewController. But we'd like that to be a part of every version of this we use. We could simply embed the DocumentVC's view into our current view and superimpose a UIActivityIndicator above it in the view stack, but that's pretty hacky. Here's a quick way we can extend any class and solve this problem
import VisionKit
import UIKit
extension VNDocumentCameraViewController {
private struct LoadingContainer {
static var loadingIndicator = UIActivityIndicatorView()
}
var loadingIndicator: UIActivityIndicatorView {
return LoadingContainer.loadingIndicator
}
func animateLoadingIndicator() {
if loadingIndicator.superview == nil {
view.addSubview(loadingIndicator)
//Setup your constraints through your favorite method
//This constrains it to the very center of the controller
loadingIndicator.frame = CGRect(
x: view.frame.width / 2.0,
y: view.frame.height / 2.0,
width: 20,
height: 20)
//Setup additional state like color/etc here
loadingIndicator.color = .white
}
loadingIndicator.startAnimating()
}
func stopAnimatingLoadingIndicator() {
loadingIndicator.stopAnimating()
}
}
The place we can call these functions are in the delegate methods for VNDocumentCameraViewController that you implement in your presenting ViewController:
func documentCameraViewController(
_ controller: VNDocumentCameraViewController,
didFinishWith scan: VNDocumentCameraScan
) {
controller.animateLoadingIndicator()
}