Refactor GenAI Image Description sample to use UI state #68

calren · 2025-08-01T20:40:26Z

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This commit refactors the GenAIImageDescription sample to use a `UiState` sealed class in the `GenAIImageDescriptionViewModel`. This improves the state management and provides a better user experience by showing the status of the feature, including download progress. The changes are based on the implementation of the GenAISummarization sample.

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Summary of Changes

Hello @calren, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly refactors the GenAI Image Description and GenAI Summarization sample applications to implement a more robust and reactive UI state management system. By introducing a comprehensive UiState sealed class, the samples now offer detailed feedback to users throughout the AI model's lifecycle, from feature availability checks and download progress to content generation and error handling. This change not only enhances the user experience with clearer status indications but also improves the maintainability and architectural clarity of the sample code.

Highlights

Unified UI State Management: Introduced a sealed class UiState for both the GenAI Image Description and GenAI Summarization samples, providing a structured way to represent various stages of AI model interaction (initial, checking status, downloading, generating, success, error).
Enhanced User Feedback: The UI now dynamically updates to show granular progress and status, such as feature download progress (bytes downloaded/total bytes) and specific error messages, significantly improving the user experience.
Improved ViewModel Architecture: Both ViewModel implementations were migrated to AndroidViewModel to properly handle Application context, and the logic was refactored to manage the new UiState flow, including cancellation of ongoing operations.
Dependency Updates: Added androidx.lifecycle.runtime.compose to both sample build.gradle.kts files to support collectAsStateWithLifecycle for lifecycle-aware state collection.

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Code Review

This pull request refactors the GenAI Image Description sample to use a UI state holder, which is a great architectural improvement. The changes align well with modern Android development practices like Unidirectional Data Flow.

My review includes a few suggestions to further improve the code:

Adhering more closely to the repository's style guide regarding AndroidViewModel.
Improving the safety of state updates by making them atomic to prevent potential race conditions and crashes.
Removing a piece of unreachable code for better clarity.

These changes will make the sample more robust and a better reference for developers.

...c/main/java/com/android/ai/samples/genai_image_description/GenAIImageDescriptionViewModel.kt

.../src/main/java/com/android/ai/samples/genai_image_description/GenAIImageDescriptionScreen.kt

...c/main/java/com/android/ai/samples/genai_image_description/GenAIImageDescriptionViewModel.kt

…b.com/android/ai-samples into refactor/genai-image-description-mvvm

.../src/main/java/com/android/ai/samples/genai_image_description/GenAIImageDescriptionScreen.kt

ksemenova · 2025-08-02T18:57:37Z

.../src/main/java/com/android/ai/samples/genai_image_description/GenAIImageDescriptionScreen.kt

+        if (uiState !is GenAIImageDescriptionUiState.Initial) {
+            val bottomSheetText = when (val state = uiState) {
+                is GenAIImageDescriptionUiState.DownloadingFeature -> stringResource(
+                    id = R.string.genai_image_description_downloading,


I see that this string doesn't accept any params:
"Downloading feature"

Should we use "image_desc_downloading" instead?
Downloading feature: %1$d / %2$d
And it looks like image_desc_downloading is never used.

Also maybe the string should be: "Downloading: %1$d of %2$d bytes"

ah yes, this should have been using image_desc_downloading, fixed

ksemenova · 2025-08-02T19:36:34Z

...c/main/java/com/android/ai/samples/genai_image_description/GenAIImageDescriptionViewModel.kt

+    ) : GenAIImageDescriptionUiState()

-    private var imageDescriber: ImageDescriber? = null
+    data class Generating(val generatedOutput: String) : GenAIImageDescriptionUiState()


Do we show generatedOutput during generation?
If yes, then maybe we can combine Generating and Success states into one? And then the generatedOutput string would have a single home.

In this case it is fine to have them in both states, because one is partial and one is complete so it is conceivable that the text UI might look different, you would also want to show that the generation is still in progress with a loading indicator. You could name them something different to make that more clear, maybe just partialOutput in generating

renamed to partialOutput here

bentrengrove · 2025-08-04T22:55:56Z

...c/main/java/com/android/ai/samples/genai_image_description/GenAIImageDescriptionViewModel.kt

+
+                        override fun onDownloadProgress(bytesDownloaded: Long) {
+                            _uiState.update {
+                                (it as? GenAIImageDescriptionUiState.DownloadingFeature)?.copy(bytesDownloaded = bytesDownloaded) ?: it


I wish I could test this somehow, but I don't think the download actually gets cancelled by the coroutine. That means this might still fire and mess with your UI state after you have set it back to initial from dismissing the bottom sheet.

The easiest way to fix is just to not support cancellation and remove the bottom sheet

okay yeah i tested it, it gets really wonky if i hide the bottom sheet while it's still downloading.

removed the bottom sheet implementation

bentrengrove · 2025-08-04T22:57:57Z

...c/main/java/com/android/ai/samples/genai_image_description/GenAIImageDescriptionViewModel.kt

+    ) : GenAIImageDescriptionUiState()

-    private var imageDescriber: ImageDescriber? = null
+    data class Generating(val generatedOutput: String) : GenAIImageDescriptionUiState()


In this case it is fine to have them in both states, because one is partial and one is complete so it is conceivable that the text UI might look different, you would also want to show that the generation is still in progress with a loading indicator. You could name them something different to make that more clear, maybe just partialOutput in generating

…b.com/android/ai-samples into refactor/genai-image-description-mvvm

calren · 2025-08-07T21:15:46Z

thanks everybody for the review!

addressed ben and kate's comments, so this is ready for another round of review

bentrengrove

One minor question but LGTM

bentrengrove · 2025-08-08T02:24:17Z

...c/main/java/com/android/ai/samples/genai_image_description/GenAIImageDescriptionViewModel.kt

+    fun clearResult() {
+        _uiState.value = GenAIImageDescriptionUiState.Initial
+        imageDescriptionJob?.cancel()
    }


Do you still need this function? If you do, you still have the same bug

ah yes, good call, removed

…b.com/android/ai-samples into refactor/genai-image-description-mvvm

google-labs-jules bot and others added 2 commits August 1, 2025 20:34

add missing dependency

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calren requested review from ksemenova and lethargicpanda as code owners August 1, 2025 20:40

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calren and others added 5 commits August 1, 2025 20:44

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Merge branch 'refactor/genai-image-description-mvvm' of https://githu…

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…b.com/android/ai-samples into refactor/genai-image-description-mvvm

Address gemini comments

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address gemini comments

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calren requested a review from bentrengrove August 1, 2025 21:03

lethargicpanda approved these changes Aug 2, 2025

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ksemenova reviewed Aug 2, 2025

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.../src/main/java/com/android/ai/samples/genai_image_description/GenAIImageDescriptionScreen.kt Outdated Show resolved Hide resolved

ksemenova reviewed Aug 2, 2025

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calren and others added 7 commits August 7, 2025 13:54

address comments

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remove bottom sheet

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🤖 Apply Spotless formatting

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Rename generatedOutput variable to partialOutput for UiState.Generating

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Merge branch 'refactor/genai-image-description-mvvm' of https://githu…

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…b.com/android/ai-samples into refactor/genai-image-description-mvvm

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bentrengrove approved these changes Aug 8, 2025

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calren and others added 3 commits August 7, 2025 21:38

Remove unused coroutine job

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Merge branch 'refactor/genai-image-description-mvvm' of https://githu…

761f390

…b.com/android/ai-samples into refactor/genai-image-description-mvvm

🤖 Apply Spotless formatting

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calren merged commit e869e79 into main Aug 8, 2025
1 check passed

calren deleted the refactor/genai-image-description-mvvm branch August 8, 2025 22:09

Refactor GenAI Image Description sample to use UI state #68

Refactor GenAI Image Description sample to use UI state #68

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