Скачать или смотреть How to Hide Loader When All Images Are Loaded on Canvas with Fabric.js

Learn how to effectively wait for all images to load on your canvas using Fabric.js, ensuring a smooth user experience by hiding loaders appropriately.
---
This video is based on the question https://stackoverflow.com/q/63914318/ asked by the user 'Ashish Soni' ( https://stackoverflow.com/u/12219794/ ) and on the answer https://stackoverflow.com/a/63914764/ provided by the user 'AndreaBogazzi' ( https://stackoverflow.com/u/2655678/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How to wait for all images are loaded from loadfromjson to canvas in fabric js?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Hide Loader When All Images Are Loaded on Canvas with Fabric.js

In web development, especially when working with graphics, one common problem developers face is displaying loaders correctly until all images are fully loaded onto a canvas. If you're using Fabric.js, you might find that your loader isn't hiding at the right time. Instead, it might disappear prematurely, giving users a poor experience while the canvas is still rendering. In this guide, we'll explore how you can ensure that your loader is only hidden after all images have truly loaded onto the canvas.

The Problem

When using the loadFromJSON() method in Fabric.js, you might expect that the loader will automatically hide once all elements in the JSON are rendered to the canvas. However, this isn't the case. The method can often lead to difficulties in managing when to hide a loader because it does not wait for asynchronous loading of each image.

You might have code that looks similar to this:

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

In the above snippet, loader.hide() is executed along with image loading events, which might not wait for all images to complete rendering before hiding the loader.

The Solution

The good news is that there's a way to effectively manage this situation by using the callback functionality offered by the loadFromJSON() method.

Step-by-Step Implementation

Show the Loader: Start by making sure that your loader is visible before you begin loading the images into your canvas. This step is crucial for informing users that something is happening in the background.

Load Images from JSON: Use the loadFromJSON() method, but instead of calling canvas.renderAll() directly, you will create a new function to encapsulate these actions.

Render the Canvas and Hide the Loader: After the images are fully loaded, call the function that renders the canvas and at the end hide the loader.

Here’s a clearer implementation of the solution:

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

Explanation of the Code

loader.show(): This makes sure the loader is visible when you initiate loading.

canvas.loadFromJSON(json, function() { ... }): Here, you define a callback function that executes once all images from the JSON are loaded.

canvas.renderAll(): This call redraws the canvas to reflect the newly added image objects.

loader.hide(): Placed at the end of the callback, this line ensures that the loader is only hidden after the canvas is successfully rendered.

Important Notes

The third argument in the original loadFromJSON() is meant for processing each object after initialization and, therefore, should not be used for handling the loader's visibility.

This approach guarantees that the loader will only hide after all images are fully loaded and rendered, leading to a much smoother user experience on your application.

Conclusion

Managing the loading state effectively is vital for creating a smooth user interface. By implementing the method as outlined above, you can ensure that your loader only disappears once all images are fully rendered on the canvas using Fabric.js. This not only enhances user experience but also makes your application appear more polished and professional.

Final Thoughts

If you implement this solution, you will observe that your application's loading behavior improves significantly. Ensuring that all elements are in place before continuing provides assurance to users and adds to your application's reliability.

Happy coding! If you have any questions or further issues related to handling loaders in Fabric.js or any other JavaScript-related topic, feel free to reach out!