触发Beforeinstallprompt事件后，添加到主屏幕不提示

Question

添加到主屏幕不提示，即使它符合所有的PWA规范，并由on Light House检查。

我已经尝试了下面的代码来检查应用程序是否已经安装。但是appinstalled事件没有被触发，并且beforeinstallprompt提示事件被成功触发。

// appinstalled

window.addEventListener('appinstalled', (evt) => { app.logEvent('a2hs', 'installed'); });

// beforeinstallprompt提示

  window.addEventListener('beforeinstallprompt', (event) => {
   event.preventDefault();
   deferredPrompt = event;
 });```

// manifest.json

`{
    "name": "demo",
    "short_name": "demo",
    "icons": [{
            "src": "/static/public/icon/icon-192x192.png",
            "sizes": "512x512",
            "type": "image/png"
        },
        {
            "src": "/static/public/icon/icon-512x512.png",
            "sizes": "192x192",
            "type": "image/png"
        }
    ],
    "start_url": "/",
    "orientation": "portrait",
    "display": "standalone",
    "theme_color": "#085689",
    "background_color": "#085689",
    "gcm_sender_id": "103xx3xxx50x",
    "gcm_user_visible_only": true
}
`

// service worker

`self.addEventListener('fetch', (event) => {
    console.log('event', event);
});`

Answer 1

从代码中删除此行

event.preventDefault();

从Chrome76开始，preventDefault()停止了自动迷你信息栏的出现

更多详细信息请点击此处

https://developers.google.com/web/fundamentals/app-install-banners/

Answer 2

 event.preventDefault(); 

这就是你的问题所在。去掉它。

Answer 3

通过删除event.preventDefault()，您将不再能够控制事件！

我建议以一种精简的方式来控制事件，并获得有关安装的信息，尝试以下代码：

window.addEventListener('beforeinstallprompt', (event) => {
   event.preventDefault();
   deferredPrompt = event;
   
   deferredPrompt.prompt();
   
   deferredPrompt.userChoice.then(result => {
          if(result.outcome === "accepted") {
            // TODO whatever you want to do when the user accept to install the app
          } else {
           // TODO whatever you want to do when the user refuse to install the app
        });
 })