Web Preloader Causes Performance Issues.

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Introduction

When building a Flutter web app, it's essential to consider the performance of the preloader, which is the loading animation displayed before the app loads. In this article, we'll discuss the potential performance issues caused by the preloader and provide a solution to improve the app's loading experience.

The Problem

When using the suggested web preloader in the Flutter documentation, some developers may experience performance issues. The preloader and its loading animation are not removed from the DOM once the Flutter web app loads, but rather made transparent, causing performance issues.

In some cases, this can lead to a slow or unresponsive app, making it difficult for users to interact with the app. For example, in some cases, users may not be able to click any buttons in the web app for several seconds.

The Solution

To improve the app's loading experience, we need to remove the preloader and its loading animation from the DOM once the app loads. We can achieve this by modifying the onAppReady method in the ShadcnApp class.

Here's an updated version of the onAppReady method:

onAppReady() {
    // Give the preloader a specific ID for more precise selection
    const loaderDiv = document.getElementById('flutter-preloader');
    
    // First fade out with transition
    loaderDiv.style.opacity = 0;
    loaderDiv.style.pointerEvents = 'none';
    
    // Then completely remove from DOM after transition completes
    setTimeout(() => {
        if (loaderDiv && loaderDiv.parentNode) {
            loaderDiv.parentNode.removeChild(loaderDiv);
        }
        
        // Clean up event listeners
        window.removeEventListener('shadcn_flutter_app_ready', this.onAppReady);
        window.removeEventListener('shadcn_flutter_theme_changed', this.onThemeChanged);
    }, 600); // Slightly longer than the 0.5s opacity transition
}

In this updated version, we first fade out the preloader with a transition, and then completely remove it from the DOM after the transition completes.

Custom Preloader Solution

To provide a more custom preloader experience, we can use a different approach. Instead of using the default preloader, we can create a custom preloader using HTML and CSS.

Here's an example of a custom preloader:

<div style="padding-right: 32px; padding-bottom: 32px; font-smooth: always; display: flex; flex-direction: column; align-items: end">
    Loading Application...
    <div id="words" style="font-size: 16px; opacity: 0.6; font-weight: 300; text-align: right; margin-top: 4px">
        ${words[Math.floor(Math.random() * words.length)]}
    </div>
</div>

In this example, we create a custom preloader using a div element with a specific style. We also use a div element with an ID of "words" to display a random message from an array of messages.

Configuring the Custom Preloader

To configure the custom preloader, we need to update the shadcn_flutter_config object. Here's an updated version of the shadcn_flutter_config object:

const shadcn_flutter_config = {
    loaderWidget: `
        <div style="padding-right: 32px; padding-bottom: 32px; font-smooth: always; display: flex; flex-direction: column; align-items: end">
            Loading Application...
            <div id="words" style="font-size: 16px; opacity: 0.6; font-weight: 300; text-align: right; margin-top: 4px">
                ${words[Math.floor(Math.random() * words.length)]}
            </div>
        </div>
    `,
    backgroundColor: null,
    foregroundColor: null,
    loaderColor: null,
    fontFamily: 'Geist Sans',
    fontSize: '24px',
    fontWeight: '400',
    mainAxisAlignment: 'end',
    crossAxisAlignment: 'end',
    externalScripts: [
        {
            src: 'https://cdn.jsdelivr.net/npm/@fontsource/geist-sans@5.0.3/400.min.css',
            type: 'stylesheet',
        },
        {
            src: 'https://cdn.jsdelivr.net/npm/@fontsource/geist-sans@5.0.3/300.min.css',
            type: 'stylesheet',
        },
    ]
};

In this updated version, we update the loaderWidget property to use the custom preloader HTML.

Conclusion

In conclusion, the web preloader can cause performance issues if not properly configured. By removing the preloader and its loading animation from the DOM once the app loads, we can improve the app's loading experience. Additionally, we can create a custom preloader using HTML and CSS to provide a more custom experience.

By following the steps outlined in this article, you can improve the performance of your Flutter web app and provide a better experience for your users.

Custom Preloader Example

Here's an example of a custom preloader:

<div style="padding-right: 32px; padding-bottom: 32px; font-smooth: always; display: flex; flex-direction: column; align-items: end">
    Loading Application...
    <div id="words" style="font-size: 16px; opacity: 0.6; font-weight: 300; text-align: right; margin-top: 4px">
        ${words[Math.floor(Math.random() * words.length)]}
    </div>
</div>

In this example, we create a custom preloader using a div element with a specific style. We also use a div element with an ID of "words" to display a random message from an array of messages.

Configuring the Custom Preloader

To configure the custom preloader, we need to update the shadcn_flutter_config object. Here's an updated version of the shadcn_flutter_config object:

const shadcn_flutter_config = {
    loaderWidget: `
        <div style="padding-right: 32px; padding-bottom: 32px; font-smooth: always; display: flex; flex-direction: column; align-items: end">
            Loading Application...
            <div id="words" style="font-size: 16px; opacity: 0.6; font-weight: 300; text-align: right; margin-top: 4px">
                ${words[Math.floor(Math.random() * words.length)]}
            </div>
        </div>
    `,
    backgroundColor: null,
    foregroundColor: null,
    loaderColor: null,
    fontFamily: 'Geist Sans',
    fontSize: '24px',
    fontWeight: '400',
    mainAxisAlignment: 'end',
    crossAxisAlignment: 'end',
    externalScripts: [
        {
            src: 'https://cdn.jsdelivr.net/npm/@fontsource/geist-sans@5.0.3/400.min.css',
            type: 'stylesheet',
        },
        {
            src: 'https://cdn.jsdelivr.net/npm/@fontsource/geist-sans@5.0.3/300.min.css',
            type: 'stylesheet',
        },
    ]
};

In this updated version, we update the loaderWidget property to use the custom preloader HTML.

Conclusion

In conclusion, the web preloader can cause performance issues if not properly configured. By removing the preloader and its loading animation from the DOM once the app loads, we can improve the app's loading experience. Additionally, we can create a custom preloader using HTML and CSS to provide a more custom experience.

Q: What is the web preloader in Flutter?

A: The web preloader is a loading animation displayed before the Flutter web app loads. It's a default feature in Flutter that helps to improve the user experience by providing a visual indication of the app's loading progress.

Q: Why does the web preloader cause performance issues?

A: The web preloader can cause performance issues if not properly configured. When the preloader is not removed from the DOM once the app loads, it can lead to a slow or unresponsive app. This is because the preloader and its loading animation are still present in the DOM, consuming resources and affecting the app's performance.

Q: How can I remove the web preloader from the DOM once the app loads?

A: To remove the web preloader from the DOM once the app loads, you need to update the onAppReady method in the ShadcnApp class. Here's an updated version of the onAppReady method:

onAppReady() {
    // Give the preloader a specific ID for more precise selection
    const loaderDiv = document.getElementById('flutter-preloader');
    
    // First fade out with transition
    loaderDiv.style.opacity = 0;
    loaderDiv.style.pointerEvents = 'none';
    
    // Then completely remove from DOM after transition completes
    setTimeout(() => {
        if (loaderDiv && loaderDiv.parentNode) {
            loaderDiv.parentNode.removeChild(loaderDiv);
        }
        
        // Clean up event listeners
        window.removeEventListener('shadcn_flutter_app_ready', this.onAppReady);
        window.removeEventListener('shadcn_flutter_theme_changed', this.onThemeChanged);
    }, 600); // Slightly longer than the 0.5s opacity transition
}

Q: Can I create a custom preloader using HTML and CSS?

A: Yes, you can create a custom preloader using HTML and CSS. To do this, you need to update the loaderWidget property in the shadcn_flutter_config object. Here's an example of a custom preloader:

<div style="padding-right: 32px; padding-bottom: 32px; font-smooth: always; display: flex; flex-direction: column; align-items: end">
    Loading Application...
    <div id="words" style="font-size: 16px; opacity: 0.6; font-weight: 300; text-align: right; margin-top: 4px">
        ${words[Math.floor(Math.random() * words.length)]}
    </div>
</div>

Q: How do I configure the custom preloader?

A: To configure the custom preloader, you need to update the shadcn_flutter_config object. Here's an updated version of the shadcn_flutter_config object:

const shadcn_flutter_config = {
    loaderWidget: `
        <div style="padding-right: 32px; padding-bottom: 32px; font-smooth: always; display: flex; flex-direction: column; align-items: end">
            Loading Application...
            <div id="words" style="font-size: 16px; opacity: 0.6; font-weight: 300; text-align: right; margin-top: 4px">
                ${words[Math.floor(Math.random() * words.length)]}
            </div>
        </div>
    `,
    backgroundColor: null,
    foregroundColor: null,
    loaderColor: null,
    fontFamily: 'Geist Sans',
    fontSize: '24px',
    fontWeight: '400',
    mainAxisAlignment: 'end',
    crossAxisAlignment: 'end',
    externalScripts: [
        {
            src: 'https://cdn.jsdelivr.net/npm/@fontsource/geist-sans@5.0.3/400.min.css',
            type: 'stylesheet',
        },
        {
            src: 'https://cdn.jsdelivr.net/npm/@fontsource/geist-sans@5.0.3/300.min.css',
            type: 'stylesheet',
        },
    ]
};

Q: Can I use a different font for the custom preloader?

A: Yes, you can use a different font for the custom preloader. To do this, you need to update the fontFamily property in the shadcn_flutter_config object. For example:

const shadcn_flutter_config = {
    // ...
    fontFamily: 'Open Sans',
    // ...
};

Q: How do I remove the custom preloader once the app loads?

A: To remove the custom preloader once the app loads, you need to update the onAppReady method in the ShadcnApp class. Here's an updated version of the onAppReady method:

onAppReady() {
    // Give the preloader a specific ID for more precise selection
    const loaderDiv = document.getElementById('flutter-preloader');
    
    // First fade out with transition
    loaderDiv.style.opacity = 0;
    loaderDiv.style.pointerEvents = 'none';
    
    // Then completely remove from DOM after transition completes
    setTimeout(() => {
        if (loaderDiv && loaderDiv.parentNode) {
            loaderDiv.parentNode.removeChild(loaderDiv);
        }
        
        // Clean up event listeners
        window.removeEventListener('shadcn_flutter_app_ready', this.onAppReady);
        window.removeEventListener('shadcn_flutter_theme_changed', this.onThemeChanged);
    }, 600); // Slightly longer than the 0.5s opacity transition
}

Conclusion

In conclusion, the web preloader can cause performance issues if not properly configured. By removing the preloader and its loading animation from the DOM once the app loads, we can improve the app's loading experience. Additionally, we can create a custom preloader using HTML and CSS to provide a more custom experience.

By following the steps outlined in this article, you can improve the performance of your Flutter web app and provide a better experience for your users.