无法安装网站：该应用已安装

Question

我已经编写了一个代码段，以将PWA Web应用程序添加到主屏幕（A2HS）。该代码运行良好。问题是，一旦我将PWA添加到主屏幕，第二次在浏览器的错误控制台中收到错误“无法安装站点：应用程序已安装”的错误。即使删除了桌面或主屏幕快捷方式，该错误也会弹出。 1.如何避免出现此错误？ 2.如何根据开发和测试的要求重新显示A2HS？

    <script type="text/javascript">
    if ('serviceWorker' in navigator) {
                window.addEventListener('load', function () {
                    navigator.serviceWorker.register('/sw.js').then(function (registration) {
                        // Registration was successful
                        console.log('ServiceWorker registration successful with scope: ', registration.scope);
                    }, function (err) {
                        // registration failed :(
                        console.log('ServiceWorker registration failed: ', err);
                    });
                });
            }

     var tra2hs = document.getElementById('tra2hs');
        var deferredPrompt;
        $('#tra2hs').hide();

        window.addEventListener('beforeinstallprompt', function(e) {
            // Prevent Chrome 67 and earlier from automatically showing the prompt
            e.preventDefault();
            // Stash the event so it can be triggered later.
            deferredPrompt = e;
            $('#tra2hs').show();
        });

        // Installation must be done by a user gesture! Here, the button click
        tra2hs.addEventListener('click', (e) => {
            // hide our user interface that shows our A2HS button
            if(deferredPrompt)
            {            
                // Show the prompt
                deferredPrompt.prompt();
                // Wait for the user to respond to the prompt
                deferredPrompt.userChoice
                    .then((choiceResult) => {
                        if (choiceResult.outcome === 'accepted') {
                            $('#tra2hs').hide();
                            console.log('User accepted the A2HS prompt');
                        } else {
                            console.log('User dismissed the A2HS prompt');
                        }
                    deferredPrompt = null;
                });
            }
        });
     </script>