Скачать или смотреть Resolving the QLayout: Cannot add a null layout to QHBoxLayout Error in PySide2

Learn how to fix the `Cannot add a null layout to QHBoxLayout` error in PySide2 by ensuring your layout methods return the correct layout objects.
---
This video is based on the question https://stackoverflow.com/q/64157778/ asked by the user 'John' ( https://stackoverflow.com/u/11839859/ ) and on the answer https://stackoverflow.com/a/64157950/ provided by the user 'eyllanesc' ( https://stackoverflow.com/u/6622587/ ) 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: PySide2 / QLayout: Cannot add a null layout to QHBoxLayout

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.
---
Understanding the QLayout: Cannot add a null layout to QHBoxLayout Error in PySide2

When working with PySide2, a common issue developers face is the QLayout: Cannot add a null layout to QHBoxLayout error. This error typically occurs when you try to add a layout that hasn't been properly initialized. Let’s dive into this problem and see how we can solve it effectively.

The Problem

In a scenario where you want to create a user interface with multiple layouts, you might attempt to organize your QHBoxLayout by separating different components into their own functions for clarity and reusability. In our case, the issue arises from separating two QVBoxLayouts into two distinct methods. The problem manifests itself as follows:

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

This error usually indicates that you've attempted to add a None value to the layout, which isn't allowed. Let’s take a closer look at the code that causes this issue.

Analyzing the Code

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

In the code above, we call self.right_panel() to add the right layout to mainLayout. However, let's take a look at the right_panel method:

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

Here, the method doesn't return the rightLayout. Thus, when you call mainLayout.addLayout(self.right_panel()), it effectively adds None. This is where the error is stemming from.

The Solution

The solution is straightforward: ensure that both layout methods return their respective QVBoxLayout instances. Here’s how you can fix the right_panel method:

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

Final Code Example

Here’s how your entire basic structure should look after applying the fix:

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

Conclusion

By ensuring that each layout function returns the corresponding layout object, you can avoid the QLayout: Cannot add a null layout to QHBoxLayout error. Structuring your code this way not only prevents issues but also enhances clarity and maintainability. Remember, a well-organized layout is key to a functional GUI!

If you encounter similar errors in your PySide2 projects in the future, don't forget to check whether your layout functions are returning their respective layout objects.