How to Get the Height of Widgets in a List Using Flutter's CustomPainter

Описание: Discover how to effectively retrieve the height of widgets in a List while using Flutter's CustomPainter, even with dynamic user-selected lists.
---
This video is based on the question https://stackoverflow.com/q/69957620/ asked by the user 'BLKKKBVSIK' ( https://stackoverflow.com/u/11550065/ ) and on the answer https://stackoverflow.com/a/70005216/ provided by the user 'BLKKKBVSIK' ( https://stackoverflow.com/u/11550065/ ) 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: Get the height of a widget in a List

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 Get the Height of Widgets in a List Using Flutter's CustomPainter

When developing applications in Flutter, especially those that involve custom painting, you may encounter situations where you need to know the dimensions of various widgets. This is particularly challenging when the widgets are contained within a list and may be dynamically selected by the user. If you have ever found yourself needing to determine the height of widgets in such scenarios, you are not alone! Here's how you can tackle this problem effectively.

Understanding the Problem

Let’s break down the issue at hand. You are working with a CustomPainter class in Flutter that takes a list of widgets. The challenge is to obtain the height of each of these widgets during the painting process so that you can adjust the paint accordingly. Here’s a simplified overview of the issues you might face:

You need the dimensions of widgets inside a list, which are user-selected and may change dynamically.

Using GlobalKeys directly on these user-selected widgets isn’t feasible due to limitations in managing numerous keys effectively.

Proposed Solution

Though it might not be the most straightforward approach, wrapping each widget in an additional widget that uses GlobalKey can help you access the dimensions of your widgets at runtime. Let me walk you through the implementation step by step.

Step 1: Creating a Subtask Wrapper

To begin with, you need to create a wrapper class for the widgets in your list. This SubtaskWrapper will use GlobalKey to keep track of its size after rendering. Here’s how you can implement it:

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

Step 2: Using the Wrapper in Your CustomPainter

Once you have your SubtaskWrapper, you can utilize it in your CustomPainter. Here’s a snippet to indicate how it might look when wrapped around your dynamic widgets:

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

Why This Approach Works

Dynamic Size Access: You utilize the lifecycle of the Flutter framework to capture the size after the widget has been laid out, ensuring you have accurate dimensions to work with.

Decoupling: This method keeps your painting logic separate from widget management, making it easier to maintain and adapt over time.

Flexibility: You can easily update where and how you want to use these size measurements by modifying the onChange callback logic.

Conclusion

In conclusion, while obtaining the height of widgets in a List for a CustomPainter can initially seem daunting, wrapping each Widget in a SubtaskWrapper provides a practical workaround. By doing so, you harness Flutter's rendering capabilities to access the size dynamically, promoting a robust and flexible painting process in your applications.

Remember, each Flutter project poses unique challenges, and with creative solutions like this, you can successfully navigate them. Happy coding!