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Discover how to send profile images to your server seamlessly using Jetpack Compose and Retrofit while avoiding common pitfalls like `400 Required Part [image] not specified`.
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This video is based on the question https://stackoverflow.com/q/77231850/ asked by the user 'Alexey' ( https://stackoverflow.com/u/19683294/ ) and on the answer https://stackoverflow.com/a/77232402/ provided by the user 'Jorn' ( https://stackoverflow.com/u/8681/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Successfully Send Images to Server Using Multipart in Jetpack Compose and Retrofit

In the world of Android development, you may find yourself in a situation where you need to upload images, like a profile picture, to a server. If you're using Jetpack Compose alongside Retrofit for networking, things can get a bit tricky. A common error that developers face during this process is the 400 Required Part [image] not specified. This blog will guide you through understanding this issue and provide a straightforward solution.

Understanding the Problem

When trying to upload an image from your Android application to the server, you might encounter an error that states:

400 Required Part [image] not specified

This error indicates that the server is expecting a specific multipart part named image, but it's not finding it. This can be frustrating, especially when you've followed the coding conventions correctly. So why does this happen?

The Source of Confusion

Consider the following code segment that nearly resembles what many developers implement:

[[See Video to Reveal this Text or Code Snippet]]

In this fragment, the multipart data is being created with the name "avatar". However, the server endpoint that you are trying to hit is expecting a part named image instead.

Fixing the Issue

Step 1: Update the Part Name

To resolve the issue, you need to modify the name of the part when creating the multipart request, ensuring it matches what the server expects. Here’s how to do it:

[[See Video to Reveal this Text or Code Snippet]]

Notice how we changed "avatar" to "image". This small change is crucial, as it aligns the client-side request with what the server is configured to receive.

Step 2: Check API Service Configuration

If you haven’t done so already, ensure your API service is configured to handle the multipart request correctly. Here’s a reminder of how it should be structured:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Handle the Image Selection Correctly

While the focus here is primarily on the multipart image upload, it’s important to ensure that the image selection process is implemented correctly. Ensure you’re using the rememberLauncherForActivityResult hook properly and handling various Android versions carefully — especially when working with images to avoid crashes or bitmap errors.

Step 4: Testing the Implementation

Once you’ve made these changes, test the implementation by running your application and performing the image upload again. If everything is set up correctly, you should no longer encounter the 400 Required Part [image] not specified error.

Conclusion

Uploading images using Jetpack Compose and Retrofit can be straightforward once you pay close attention to the expected parameters of your API. The key issue of 400 Required Part [image] not specified can typically be traced back to naming discrepancies in your multipart requests. By ensuring that your part names match what your server expects, you can avoid this problem and achieve successful uploads.

If you run into other obstacles, remember to inspect your API methods and body configurations carefully. Happy coding!