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GemAI requires a valid Google Gemini API key to communicate with the AI models. This guide walks you through obtaining, configuring, and validating your API key.

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Getting your API key

1

Visit Google AI Studio

Navigate to Google AI Studio to generate your API key.
2

Create or select a project

Choose an existing Google Cloud project or create a new one to associate with your API key.
3

Generate the API key

Click “Create API Key” and copy the generated key. Store it securely as you’ll need it to configure GemAI.
Never commit your API key to version control or share it publicly. Treat it like a password.

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Saving the API key

GemAI uses the SaveApiKeyUseCase to securely store your API key in the app’s DataStore. The key is persisted locally and encrypted by the Android system.
SaveApiKeyUseCase.kt
class SaveApiKeyUseCase
@Inject
constructor(
    private val apiKeyRepository: ApiKeyRepository,
    @Dispatcher(GemAIDispatchers.IO) private val dispatcher: CoroutineDispatcher,
) : BaseUseCase<String, Result<Unit, ApiKeyError>> {
    override suspend fun perform(parms: String): Result<Unit, ApiKeyError> =
        withContext(dispatcher) { apiKeyRepository.saveApiKey(parms) }
}
The repository implementation stores the key in Protocol Buffers format:
DatastoreRepositoryImpl.kt
override suspend fun saveApiKey(apiKey: String) {
    dataStore.updateData { config -> 
        config.toBuilder().setApiKey(apiKey).build() 
    }
}

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Retrieving the API key

To retrieve the stored API key, GemAI uses the GetApiKeyUseCase:
GetApiKeyUseCase.kt
class GetApiKeyUseCase
@Inject
constructor(
    private val apiKeyRepository: ApiKeyRepository,
    @Dispatcher(GemAIDispatchers.IO) private val dispatcher: CoroutineDispatcher,
) : BaseUseCase<Unit, Result<String, ApiKeyError>> {
    override suspend fun perform(): Result<String, ApiKeyError> =
        withContext(dispatcher) { apiKeyRepository.getApiKey() }
}

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Validating the API key

Before saving an API key, you should validate it to ensure it works correctly. GemAI provides a testKey() function in the ModelBuilder class:
ModelBuilder.kt
suspend fun testKey(key: String): Boolean {
    return try {
        GenerativeModel(apiKey = key, modelName = AIModel.GEMINI_1_5_FLASH.modelName)
            .generateContent("Hi, how are you?")
        true
    } catch (e: Exception) {
        e.printStackTrace()
        false
    }
}
The validation function sends a simple test message to the Gemini API using the gemini-1.5-flash model. If the request succeeds, the key is valid.

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How it works

The testKey() function:
  1. Creates a temporary GenerativeModel instance with the provided API key
  2. Sends a test prompt (“Hi, how are you?”) to the Gemini API
  3. Returns true if the request succeeds, false if an exception occurs

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User configuration

The API key is stored as part of the UserConfig data class:
UserConfig.kt
data class UserConfig(
    val model: AIModel, 
    val apiKey: String?, 
    val hasApiKey: Boolean
) {
    companion object {
        val DEFAULT = UserConfig(
            model = AIModel.GEMINI_1_5_FLASH, 
            apiKey = null, 
            hasApiKey = false
        )
    }
}
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apiKey
String?
The stored API key, or null if not yet configured
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hasApiKey
Boolean
Flag indicating whether a valid API key has been saved
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model
AIModel
The selected AI model to use with the API key

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Security best practices

Follow these guidelines to keep your API key secure:
  • Never hardcode API keys in your source code
  • Use environment variables or secure storage mechanisms during development
  • Rotate keys regularly if you suspect they’ve been compromised
  • Monitor usage in the Google Cloud Console to detect unauthorized access
  • Enable billing alerts to catch unexpected API usage

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Troubleshooting

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Invalid API key error

If the testKey() function returns false, verify:
  • The API key is copied correctly without extra spaces
  • The API key is enabled in Google Cloud Console
  • The Generative AI API is enabled for your project
  • Your Google Cloud project has billing enabled

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Key not persisting

If your API key doesn’t persist between app sessions:
  • Check that DataStore has write permissions
  • Verify the app isn’t clearing data on restart
  • Ensure the SaveApiKeyUseCase is being called successfully

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