Flutter web app progress indicator before loading app?

问题

Hi I am a mobile app developer and not much familiar with web development, I was finding any approach to implement Progress Indicator before loading the flutter web app like Gmail loading screen. Flutter web is cool but it takes few moments before loading the app. Can we add any indicator for this loading duration? Any code implemented in flutter would be the part of flutter app and it won't work, There should be another approach to achieve this.

回答1:

In your question you mentioned

Any code implemented in flutter would be the part of flutter app and it won't work,...

I assume you tried to add the splash screen approach for android or IOS. Since flutter-web is simply an index.html and a couple of js files(for eg., main.dart.js), you should perhaps try the CSS loading animation trick. Since you didn't share any code I am not writing any code but the following would be my approach as explained by this red stapler video. He/she kindly provided a lot of CSS based animations here along with the codepen implementations for that.

So following would be my steps in the flutter_web_project\web\index.html file.

Add a span element in the body of index.html to show the css animation itself.
Create a div wrapper to position the span animation in your index.html.
Then listen to the onLoad event of the window and remove the div element from your page or fade it out as described in the video.

回答2:

With the help of @Abhilash, I was able to accomplish this. I got loader code from w3schools.

My project/web/index.html is like this.

<html>

<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script defer src="index.dart.js" type="application/javascript"></script>

    <style>
        .loading {
            display: flex;
            justify-content: center;
            align-items: center;
            margin: 0;
            position: absolute;
            top: 50%;
            left: 50%;
            -ms-transform: translate(-50%, -50%);
            transform: translate(-50%, -50%);
        }

        .loader {
            border: 16px solid #f3f3f3;
            border-radius: 50%;
            border-top: 16px solid blue;
            border-right: 16px solid green;
            border-bottom: 16px solid red;
            border-left: 16px solid pink;
            width: 120px;
            height: 120px;
            -webkit-animation: spin 2s linear infinite;
            animation: spin 2s linear infinite;
        }

        @-webkit-keyframes spin {
            0% {
                -webkit-transform: rotate(0deg);
            }

            100% {
                -webkit-transform: rotate(360deg);
            }
        }

        @keyframes spin {
            0% {
                transform: rotate(0deg);
            }

            100% {
                transform: rotate(360deg);
            }
        }
    </style>
</head>

<body>
    <div class="loading">
        <div class="loader"></div>
    </div>

    <script src="main.dart.js" type="application/javascript"></script>
</body>

</html>

来源：https://stackoverflow.com/questions/57209754/flutter-web-app-progress-indicator-before-loading-app

标签

Flutter

flutter-web