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Discover how to retain the widths of `TableColumn` in your JavaFX TableView by using `minWidth`. This guide walks you through the effective solution for managing column resizing while maintaining auto-scaling features.
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This video is based on the question https://stackoverflow.com/q/64747452/ asked by the user 'Willem Kunkels' ( https://stackoverflow.com/u/14604034/ ) and on the answer https://stackoverflow.com/a/64775897/ provided by the user 'swpalmer' ( https://stackoverflow.com/u/1165724/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Preserving TableColumn Widths in JavaFX TableView on Restart

When developing JavaFX applications, managing user preferences such as layout and column widths can greatly enhance the user experience. Particularly, if you have a TableView where users can customize their view by resizing columns, it's essential to save and restore these adjustments when the application restarts. In this guide, we'll explore an effective solution to preserve the widths of TableColumn while maintaining the auto-resizing feature of the TableView.

The Challenge

In your JavaFX application, you faced a common issue:

You successfully saved and restored the index of each TableColumn on application shutdown.

However, when you attempted to restore the preferred width of these columns after a restart, it didn't work as expected.

You noticed that while you could correctly set the order of your columns, the preferred width (prefWidth) wasn't being honored. The likely culprit was the CONSTRAINED_RESIZE_POLICY, which allows the TableView to adjust its columns automatically when the main application window resizes. Unfortunately, this didn't allow for setting a fixed width on the columns.

The Solution

To tackle this problem, the effective approach involves using minWidth instead of prefWidth for your columns. Here’s a step-by-step breakdown of how to implement this solution:

Step 1: Set the Minimum Width

Instead of directly assigning the prefWidth, you’ll want to start by setting the minWidth of each TableColumn. Here’s how you can implement this:

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

Step 2: Fix minWidth After UI Loads

One crucial aspect to ensure that your columns work correctly after being rendered is to "fix" the minWidth a few moments after the UI has loaded. This can be done using a PauseTransition to introduce a short delay, allowing the JavaFX rendering engine to finish processing the UI layout.

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

Benefits of this Approach

User Preference Retention: This method effectively retains the user’s chosen column widths on restart.

Maintains Auto-Scaling: By using CONSTRAINED_RESIZE_POLICY, you enable the TableView to adjust its columns based on the application window size while still respecting user-defined widths.

Conclusion

In summary, to preserve the widths of TableColumn in your JavaFX TableView, replace the prefWidth setting with minWidth initially. Then, after a brief delay once your UI has been displayed, you can set the prefWidth back to align with user preferences. This approach strikes a good balance between maintaining customizable layouts and auto-scaling the table.

If you implement these steps, you’ll ensure that your users have a consistent experience each time they open your application. Happy coding!