How to Properly Download and Display Images in Unity Using URLs

Discover the correct approach to download and display images from URLs for multiple buttons in Unity without overwriting the images.
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This video is based on the question https://stackoverflow.com/q/65915923/ asked by the user 'James Threepat' ( https://stackoverflow.com/u/15090128/ ) and on the answer https://stackoverflow.com/a/65917348/ provided by the user 'derHugo' ( https://stackoverflow.com/u/7111561/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Downloading Images from URLs in Unity: A Common Problem

If you’re working with Unity and trying to download images from URLs to display on buttons, you might run into an issue where only the last button's image is displayed, while previous ones remain blank or show incorrect images. This guide will help you understand why this happens and how to solve the issue effectively.

Understanding the Problem

When you’re iterating through a collection of users to create buttons and set images, it can be misleading if the images aren't showing as intended. The core of the problem lies in how references are managed in your loop.

What Happens?

In your original code:

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

You’re repeatedly assigning the same imageToUpdate field reference while looping through each user. As each coroutine runs, it modifies the same reference, resulting in only the last image being displayed. This is a common pitfall when working with asynchronous calls like coroutines in Unity.

The Solution: Passing References Correctly

The key to resolving this issue is to pass the specific Image component reference to your downloadImage coroutine instead of using a class-level field. Below is the revised code and an explanation of the changes.

Refactored Code

Here’s the updated CreateButton method and the adjusted downloadImage coroutine:

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

Breakdown of Changes

Pass Image Reference:

We've removed the class-level imageToUpdate variable and instead, we're passing the Image component directly as an argument to the downloadImage coroutine. This ensures each button gets its own image.

Using 'using' for UnityWebRequest:

The using statement for www ensures that resources are cleaned up properly after use, helping with memory management.

Simplified Error Handling:

Always check for errors after the request to handle network issues appropriately.

Conclusion

By properly passing the Image component reference to your coroutine, you avoid the common mistake of overwriting the reference during each iteration of your loop. This change allows each button to display the correct image without conflict.

Next Steps

Try implementing this solution in your project.

Experiment with other asynchronous tasks in Unity to further your understanding and improve your coding practices.

By understanding how Unity's coroutine and reference handling work, you can avoid common pitfalls and improve your game development skills!