Flutter: `The method 'DataPart' isn't defined` when using firebase_ai for Gemini Vision

Question

I'm trying to send an image and text to Gemini using the firebase_ai package in Flutter, but I'm getting a persistent error: The method 'DataPart' isn't defined for the type 'AiAssistantService'.

The strange thing is that I am using the official code structure from the examples.

Here is my function:

import 'dart:typed_data';
import 'package:firebase_ai/firebase_ai.dart';
// ... other imports

Future<void> getResponseForImage(String userInput, Uint8List imageBytes) async {
  try {
    final googleAI = FirebaseAI.googleAI();

    final model = googleAI.generativeModel(
      model: 'gemini-1.5-flash-latest',
    );

    // According to docs, this should be the correct way to structure the content
    final content = [
        TextPart("Some text prompt"),
        DataPart('image/jpeg', imageBytes), // <-- The error happens here
    ];

    final response = await model.generateContent(content);
    print(response.text);

  } catch (e) {
    print("An error occurred: $e");
  }
}

I was expecting the code to work correctly without any errors. Instead, I always get the error: 'DataPart' isn't defined.

I have already tried many things to fix this:

I ran 'flutter clean'.
I deleted the pubspec.lock file and ran 'flutter pub get'.
I ran 'flutter pub cache repair'.
I restarted VS Code many times.

None of these solutions worked.

Hello, thank you for your comment and my apologies for the confusion. This is the CORRECT official package page that I am following on pub.dev: pub.dev/packages/firebase_ai The code example under the "Multi-modal input" section on that page shows the exact structure that I am using, but I still get the DataPart is not defined error. — Qasid Khyar
– Qasid Khyar, Commented Oct 3 at 18:32
I don't seem to be able to find that on that page. Rosario's suggestion the other hand seems like what you might be looking for. — Joe Spiro
– Joe Spiro, Commented Oct 6 at 12:54

Rosário P. Fernandes · Accepted Answer · 2025-10-04 00:14:38Z

I can't find the documentation that you claim to see in pub.dev, but the official Firebase documentation suggests that you should use InlineDataPart.

So your code would become:

Future<void> getResponseForImage(String userInput, Uint8List imageBytes) async {
  try {
    final googleAI = FirebaseAI.googleAI();

    final model = googleAI.generativeModel(
      model: 'gemini-2.5-flash',
    );

    // Note the use of Content.multi():
    final content = Content.multi([
        TextPart("Some text prompt"),
        InlineDataPart('image/jpeg', imageBytes)
    ]);

    final response = await model.generateContent([content]);
    print(response.text);

  } catch (e) {
    print("An error occurred: $e");
  }
}

Also note that I changed the model name from gemini-1.5-flash-latest to gemini-2.5-flash because the Gemini 1.5 models were turned down last month.

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