Screenshot showing up blank in Compose Multiplatform for iOS

Question

I've been trying to implement ability to take a screenshot for both Android and iOS using Compose Multiplatform but for iOS is returning a blank image. Android works as expected.

Please find below the code that I am using. Any thoughts?

class IosScreenshot : ScreenshotInterface {
    override fun takeScreenshot(): String? {
        val window = UIApplication.sharedApplication.keyWindow ?: return null
        UIGraphicsBeginImageContextWithOptions(window.bounds.useContents { CGSizeMake(size.width, size.height) }, false, 0.0)
        window.layer.renderInContext(UIGraphicsGetCurrentContext())
        val uiImage = UIGraphicsGetImageFromCurrentImageContext() ?: return null
        UIGraphicsEndImageContext()
        val img = UIImagePNGRepresentation(uiImage)
        return img?.base64EncodedStringWithOptions(options = NSDataBase64Encoding64CharacterLineLength)
    }
}

Answer 1

The issue is from how the view's layer is being rendered. try replacing layer.render(in:) with drawHierarchy(in:afterScreenUpdates:)

Sample

class IosScreenshot : ScreenshotInterface {
    override fun takeScreenshot(): String? {
      guard let window = UIApplication.shared.keyWindow else { return nil }
      UIGraphicsBeginImageContextWithOptions(window.bounds.size, false, 0.0)
    
    // Make sure the complete view hierarchy is rendered.
      window.drawHierarchy(in: window.bounds, afterScreenUpdates: true)
    
      guard let uiImage = UIGraphicsGetImageFromCurrentImageContext() else {
        UIGraphicsEndImageContext()
        return nil
    }
    UIGraphicsEndImageContext()
    

    guard let img = UIImagePNGRepresentation(uiImage) else { return nil }
    return img.base64EncodedString(options: .lineLength64Characters)
   }
}