Flutter Web Loading Tips

Flutter.Web.smooth.loading.mov

Introduction

User experience is essential in the software development world, and the loading process is a crucial aspect often overlooked. A slow or clunky loading experience can frustrate users and cause them to abandon your app before it even has a chance to load your Flutter Web app.

Key Features

Smooth Progress Bar: Create an elegant progress bar that reflects the loading progress of your Flutter Web application.
Graceful Fading: Implement a graceful fading effect for the progress bar upon loading completion.
Seamless Transition: Ensure a seamless transition from the loading screen to displaying your Flutter content.

Getting Started

To get started with improving your Flutter Web loading experience, follow these steps:

Clone the Repository: Begin by cloning this repository to your local development environment.

git clone https://github.com/monster555/flutter_web_loading_tips.git

Enhance Your App: Apply the techniques learned from the guide to your Flutter Web project, and watch as your loading experience becomes smoother and more professional.

See How Smooth the Loading Experience is on FaceFolio

This is one of my portfolio projects. To see the smooth loading experience in action, visit the FaceFolio homepage.

Step-by-Step

Improving the loading experience in your Flutter Web application involves just a few steps. Follow each step closely to ensure proper implementation. The provided code snippets should be integrated into your project as described.

Step 1: Adding Progress Bar Elements in index.html

In your index.html file, add the following <div> elements to display the progress bar. These will visually represent the loading progress of the Flutter Engine.

<!-- Create a progress bar container with a nested progress bar -->
<div class="progress-container" id="progress">
  <div class="progress-bar" id="progressbar"></div>
</div>

Step 2: Adding the Script in `flutter_bootstrap.js`

To ensure the proper initialization of your Flutter app using the new method available in Flutter 3.22 and later, you need to update the web/flutter_bootstrap.js file (not the build/web/flutter_bootstrap.js, which is auto-generated during the build process and will be overwritten).

Below is an example of how your web/flutter_bootstrap.js file should look with the necessary changes in place:

    /**
    * This function creates a delay of 500 milliseconds.
    *
    * @returns {Promise} A Promise that resolves after the delay.
    */
    function addDelay() {
        return new Promise((resolve) => setTimeout(resolve, 500));
    }

    // Get the progress and progressBar elements from the DOM
    const progress = document.getElementById("progress");
    const progressBar = document.getElementById("progressbar");

    // Initialize the width of the progress bar to 0%
    progress.style.width = `0%`;

    {{flutter_js}}

    progress.style.width = `33%`;

    {{flutter_build_config}}

    // Load the Flutter engine
    _flutter.loader.load({
        onEntrypointLoaded: async function(engineInitializer) {
            // Update the progress bar to 66% after the engine is loaded
            progressBar.style.width = `66%`;

            // Initialize the Flutter engine.
            const appRunner = await engineInitializer.initializeEngine();
    
            // Set progress to 100% before adding a delay.
            progressBar.style.width = `100%`;
            
            // Add a delay bofreo running the app to create a smooth crossfade effect.
            await addDelay();
            
            // Hide the progress bar by reducing its opacity.
            // This will create the fade out effect by animating the opacity.
            progress.style.opacity = 0;
    
            // Run the Flutter app.
            await appRunner.runApp();
    
            // Add a fade-in effect to the Flutter view element.
            document.querySelector("flutter-view").classList.add("fade-in");
        }
    });

Step 3: Creating `style.css`

Create a style.css file with the following content to style the progress bar and create the fade-in effect:

/* Styles for the body element */
body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    background-color: #fff;
}

/* Styles for the progress bar container */
.progress-container {
    width: 300px;
    height: 8px;
    background-color: #e0e0e0;
    border-radius: 10px;
    overflow: hidden;
    transition: opacity 0.25s ease-out;
}

/* Styles for the progress bar */
.progress-bar {
    display: block;
    height: 100%;
    background-color: #6a6a6a;
    width: 0;
    transition: width 0.5s ease;
}

/* CSS for a fade-in animation */
.fade-in {
    opacity: 0;
    animation: fadeIn 1s ease-in-out forwards;
}

/* Keyframes for the fadeIn animation */
@keyframes fadeIn {
    0% {
        opacity: 0;
    }
    60% {
        opacity: 0;
    }
    100% {
        opacity: 1;
    }
}

Step 4: Referencing `style.css`

In your index.html, reference the style.css file to apply the defined styles:

<link rel="stylesheet" href="style.css" />

By following these steps, you can implement a smooth loading experience in your Flutter Web application.

License

This project is licensed under the MIT License - see the LICENSE file for details.

monster555/flutter_web_loading_tips