iOS 按钮可点击但不可见

Question

I have a view(let's call it scanView) that opens camera to scan for QR Codes. I have placed a button on it which opens or closes the flash. The problem i am facing is that the button is getting clicked but it is not visible, i,e, I can turn flash on or off by clicking on screen where i placed the button, but the button is not visible. I checked the Alpha of button, tried bringing subview to front also. Nothing works. Is it some issue related to QR reader of iOS? Here is the implementation of QR Reader:

        captureSession = AVCaptureSession()

        guard let videoCaptureDevice = AVCaptureDevice.default(for: .video) else { return }
        let videoInput: AVCaptureDeviceInput

        do {
            videoInput = try AVCaptureDeviceInput(device: videoCaptureDevice)
        } catch {
            return
        }

        if (captureSession.canAddInput(videoInput)) {
            captureSession.addInput(videoInput)
        } else {
            failed()
            return
        }

        let metadataOutput = AVCaptureMetadataOutput()

        if (captureSession.canAddOutput(metadataOutput)) {
            captureSession.addOutput(metadataOutput)

            metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
            metadataOutput.metadataObjectTypes = [.qr]
        } else {
            failed()
            return
        }

        previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        previewLayer.frame = scanView.layer.bounds
        previewLayer.videoGravity = .resizeAspectFill
        
        scanView.layer.addSublayer(previewLayer)
        captureSession.startRunning()

As you can see above I have added a background color and background image too for clarity. According to me the button looks fine in hierarchy. On this scanView, I am adding the button from my xib file

Answer 1

First, it is not related to QR Reader implementation probably.

Second, ask yourself how the button is supposed to be seen? Title? Image?

Third, you can always press 'Debug View Hierarchy' button while running the app, to stop its execution and to see all the views present on the screen.

'Debug View Hierarchy' button in on the same Debug Tools pane below where other debugging tools (like breakpoints) are placed.

Answer 2

Learn how to use Debug View Hierarchy , so you can clearly see where the button is on the screen and why it's not visible.

I think you have a problem with the image of the button because you are able to click on the button but are not able to see it, make sure the image is added properly on to the button.

Keep one thing in mind, that if it is clickable, then it is there, focus on its presentation. Also try to add a background color to it and remove the image, just to make sure your other implementation is working properly.

Answer 3

I managed to solve the issue by setting the zposition of the button. Thank you for your time everyone