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Refactor the UI layout of ImagenScreen to solve the navigation flicker #1719

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Refactor the UI layout of ImagenScreen to solve the navigation flicker #1719

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f60ea50
change ImagenScreen UI from ZStack to ScrollView
YoungHypo Jun 25, 2025
0a3b325
change fix size of images to flexible
YoungHypo Jun 26, 2025
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36 changes: 16 additions & 20 deletions firebaseai/ImagenScreen/ImagenScreen.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ struct ImagenScreen: View {
var focusedField: FocusedField?

var body: some View {
ZStack {
ScrollView {
VStack {
InputField("Enter a prompt to generate an image", text: $viewModel.userInput) {
Image(
Expand All @@ -44,28 +44,24 @@ struct ImagenScreen: View {
.focused($focusedField, equals: .message)
.onSubmit { sendOrStop() }

ScrollView {
let spacing: CGFloat = 10
LazyVGrid(columns: [
GridItem(.fixed(UIScreen.main.bounds.width / 2 - spacing), spacing: spacing),
GridItem(.fixed(UIScreen.main.bounds.width / 2 - spacing), spacing: spacing),
], spacing: spacing) {
ForEach(viewModel.images, id: \.self) { image in
Image(uiImage: image)
.resizable()
.aspectRatio(contentMode: .fill)
.frame(width: UIScreen.main.bounds.width / 2 - spacing,
height: UIScreen.main.bounds.width / 2 - spacing)
.cornerRadius(12)
.clipped()
}
let spacing: CGFloat = 10
LazyVGrid(columns: [
GridItem(.fixed(UIScreen.main.bounds.width / 2 - spacing), spacing: spacing),
GridItem(.fixed(UIScreen.main.bounds.width / 2 - spacing), spacing: spacing),
], spacing: spacing) {
ForEach(viewModel.images, id: \.self) { image in
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medium

Using id: \.self with UIImage can cause performance issues because UIImage is a class. When images are regenerated, new UIImage instances cause SwiftUI to re-render the entire grid. Consider wrapping UIImage in a custom struct that conforms to Identifiable (e.g., using a UUID for the id) to improve UI performance.

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@YoungHypo YoungHypo Jun 26, 2025 •
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I’ve tried to generate images multiple times in imagenscreen. The UI remained smooth without noticeable lag when re-rendering the image grid. If you think adjustments are necessary, I'll do that. @paulb777

Image(uiImage: image)
.resizable()
.aspectRatio(contentMode: .fill)
.frame(width: UIScreen.main.bounds.width / 2 - spacing,
height: UIScreen.main.bounds.width / 2 - spacing)
.cornerRadius(12)
.clipped()
}
.padding(.horizontal, spacing)
}
.padding(.horizontal, spacing)
}
if viewModel.inProgress {
ProgressOverlay()
}
.overlay(viewModel.inProgress ? ProgressOverlay() : nil)
}
.navigationTitle("Imagen example")
.onAppear {
Expand Down