Скачать или смотреть Flutter: How to Execute a Function in the Build Method Only Once?

Discover how to ensure a function in your Flutter app's build method runs only once! Learn efficient methods to optimize your Flutter workflow.
---
This video is based on the question https://stackoverflow.com/q/70223421/ asked by the user 'who-aditya-nawandar' ( https://stackoverflow.com/u/2110393/ ) and on the answer https://stackoverflow.com/a/70223485/ provided by the user 'h8moss' ( https://stackoverflow.com/u/12638504/ ) 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: Flutter - How to execute a function only once in build method?

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.
---
Flutter: How to Execute a Function in the Build Method Only Once?

In the world of Flutter development, optimizing performance is crucial. A common challenge developers face is ensuring that certain functions, particularly those that build widgets, execute only once during the lifecycle of a widget. This guide addresses this issue by offering clear solutions tailored for Flutter applications.

The Problem

Imagine you have a screen in your Flutter app where you need to render a widget based on a particular condition – let's say, when a workout ID is available. You may use a function to build a widget that displays data from completed exercises. However, every time the build method executes, this function could run again, potentially leading to unnecessary processing or repeated state changes.

Example Code Snippet

Consider the following piece of code for reference:

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

In this example, the function _buildDataTableForCompletedExercises needs to run only once during the widget's lifecycle. So how can we achieve this?

The Solution

There are two primary methods to execute a function only once in the build method:

Method 1: Use initState to Cache the Result

The simplest solution is to cache the result of the function in the initState method of your stateful widget. Let’s break down the steps:

Declare a nullable Widget: Before the initState, declare a variable to hold the cached widget.

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

Assign in initState: Use the initState method to call your function and store the result.

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

Use in build method: Finally, use the _completedExercises variable when rendering your widget.

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

By doing this, the function is executed only once when the widget initializes, and every subsequent build will reference the cached value.

Method 2: Cache Inside the Function Itself

If you prefer to keep the caching mechanism closer to the function, modify the function itself to return a cached value if it has already been created.

Modify the Function:

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

With this approach, the first call generates the widget, and all further calls will return the already created instance of the widget.

Conclusion

Running a function only once in the Flutter build method can significantly enhance your app's performance and responsiveness. By caching the widget either in the initState method or within the function itself, you ensure that your application behaves smoothly and efficiently.

Optimize your Flutter applications by incorporating these techniques, and enjoy a more fluid user experience! If you have further questions or need assistance with Flutter, feel free to reach out in the comments below. Let's build something great together!