Скачать или смотреть Resolving the Invalid or Deleted Object Error in Matlab App Designer

Learn how to effectively manage point handles in your Matlab App Designer, preventing errors when deleting or moving points with practical solutions and example code.
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Resolving the Invalid or Deleted Object Error in Matlab App Designer: A Step-by-Step Guide

When working with the Matlab App Designer, especially while creating a GUI for image processing with interactive point selection, you might encounter errors when attempting to access positions of points after deleting or moving them. One such error is the Invalid or deleted object error which occurs when you try to access a point handle that no longer exists. This post will delve into how to correctly refresh point handles to avoid these issues, providing clear steps and sample code along the way.

Understanding the Problem

In your app, you have configured two buttons:

Load Image Button: Loads an image and allows the user to mark points until they press the escape key.

Position Button: Prints out the coordinates of the marked points.

After deleting a point, when you hit the Position Button, you may see an error indicating that the point object is invalid or deleted.

The Example Error

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

In order to avoid this issue, it’s crucial to check the validity of the point handles before accessing them.

Solution: Refreshing the Point Handles

Step 1: Validate Point Handles

Before accessing any point handles, you should ensure they are still valid. This can be in the PositionButtonPushed function, where you can loop through the pointhandles and validate each one.

Here’s a robust solution:

Code Example

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

Step 2: Implementing a Cleanup Function

You might also consider implementing a separate function to check the validity of all handles. This way, you can keep your code clean and reusable.

Code Example for Cleanup Function

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

Step 3: Testing Your Solution

After implementing these changes, test your app to ensure that:

The application does not throw errors when points are deleted before clicking the Position Button.

The coordinates output correctly reflects the existing points.

Conclusion

By validating point handles before accessing their properties, you can effectively avoid errors related to invalid or deleted objects in your Matlab App Designer application. Implementing a cleanup function keeps your code organized and ensures a smooth user experience.

With these strategies, you can handle point management efficiently, allowing for a more reliable and interactive GUI in Matlab. Happy coding!