Скачать или смотреть How to Conditionally Render Widgets in Flutter

Learn how to conditionally render in Flutter widgets based on specific criteria, ensuring optimal UI performance and better user experience.
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This video is based on the question https://stackoverflow.com/q/66648897/ asked by the user 'Febin Johnson' ( https://stackoverflow.com/u/13362666/ ) and on the answer https://stackoverflow.com/a/66649408/ provided by the user 'Simon Sot' ( https://stackoverflow.com/u/13701546/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Conditionally Render Widgets in Flutter

In the world of Flutter development, conditional rendering is a powerful tool that allows developers to control which widgets appear on screen under certain conditions. This technique is especially useful when we want to present dynamic content based on user inputs or data changes.

The Problem: Hiding a Widget Based on Wallet Amount

Imagine you have a wallet circle widget that visually represents a balance. When the balance is zero, you want the widget to be completely hidden from view. The challenge arises when you need to implement this in Flutter.

The original approach used a ternary operator within a CustomPaint widget. However, it led to some confusion on how to effectively hide the widget when the wallet amount hits zero.

Understanding the Solution

To achieve the desired outcome of hiding the wallet circle widget when the total is zero, we can still use a ternary operator, but we need to place it correctly in the widget tree. Here’s how to do it:

Step-by-Step Breakdown

Condition Check: First, you need to check if the wallet amount (this.total) is less than or equal to zero.

CustomPaint Configuration: If the condition is true, return a CustomPaint widget configured with colors representing an empty state (for instance, a color like red).

Else Case: When the condition is false, use an empty Container() to ensure no widget is rendered.

Here’s the Code Implementation

Here is how you can set it up in your Flutter code:

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

Key Points to Remember

Placement of Ternary Operator: Make sure the ternary operator is used to select between a CustomPaint and an empty Container()—moving it outside the CustomPaint configuration can help simplify your logic.

Maintain UI Consistency: By rendering an empty Container(), you maintain the layout and prevent visual disruptions when the wallet amount changes.

Conclusion

By using conditional rendering in Flutter wisely, you can create a more engaging and user-friendly interface. The ability to show or hide widgets based on changing data states is essential in delivering a dynamic experience. Implementing the correct logic using a ternary operator can simplify this process and keep your code clean.

Now, you have the knowledge to efficiently tackle similar challenges in Flutter. Happy coding!