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问题:

I've created a mobile-friendly web site with jQuery Mobile and added some meta info so that it should be pinned to iOS and Android homescreens and should be launched as a web app (in other words: in a browser, but without browser navigation elements).

It works fine for iOS, but it doesn't work for Android 4.4.2.

I followed this tutorial for creating Android-Compatible web apps:

Despite adding all the meta info as listed in the tutorial, Android does show the "Add to homescreen" button for my web site, but it does not launch the website without browser navigation elements as described in the tutorial.

What am I doing wrong?

回答1:

As you can see here this feature is still tagged as Beta. I guess you'll need to test this feature with the latest version of Chrome. From the article:

Supporting add to homescreen apps

Chrome will look for the following meta tag in the element of the web-page:

<meta name="mobile-web-app-capable" content="yes">

The name attribute MUST be "mobile-web-app-capable" and the content attribute must be "yes" (case in-sensitive). If there is any other value in the content attribute the web app will be added as a regular bookmark.

Icon

The icon that is used to install to the homescreen is determined by using the largest icon found in one of the following <link> tags:

<link rel="shortcut icon" sizes="192x192" href="nice-highres.png"> (recommended)
<link rel="shortcut icon" sizes="128x128" href="niceicon.png">
<link rel="apple-touch-icon" sizes="128x128" href="niceicon.png">
<link rel="apple-touch-icon-precomposed" sizes="128x128" href="niceicon.png">

Caution: The 192px image format is recommended. The last two formats (apple-touch-*) are deprecated, and will be supported only for a short time.

Icon label

The application’s <title> element serves as the default label for the icon on the homescreen.

Configuration

The following example is the minimum required configuration to support a homescreen launch experience.

<!doctype html>
<html>
   <head>
     <title>Awesome app</title>
     <meta name="viewport" content="width=device-width">
     <meta name="mobile-web-app-capable" content="yes">
     <link rel="shortcut icon" sizes="192x192" href="/icon.png">
   </head>
   <body></body>
</html>

Comparison to iOS Safari Add to Homescreen

Chrome will also allow Web Apps to launch in "App mode" if they embed a meta tag using the "apple-mobile-web-app-capable" name. Chrome will stop supporting this usage in an upcoming release. Chrome currently shows a deprecation warning in the Developer Tools’ console log when it detects a page with only the "apple-mobile-web-app-capable" meta tag. The warning appears as follows:

Whilst Chrome temporarily accepts the usage of "apple-mobile-web-app-capable", Chrome does not offer compatibility with the iOS Safari API’s including:

window.navigator.standalone
<meta name="apple-mobile-web-app-status-bar-style" content="black">
<link rel="apple-touch-startup-image" href="/startup.png">

I hope it helps.

回答2:

The guide indicates that as of Chrome 68 it is expected that the app developer adds a button to their app. And that it should only work if the PWA criteria are met. Then you should be able to use the following code to get a callback to your app where you can show a button to the user to kick off the Add to home screen prompt.

Per the guide, add this listener.

let deferredPrompt;

window.addEventListener('beforeinstallprompt', (e) => {
  // Prevent Chrome 67 and earlier from automatically showing the prompt
  e.preventDefault();
  // Stash the event so it can be triggered later.
  deferredPrompt = e;
  // Update UI notify the user they can add to home screen
  btnAdd.style.display = 'block';
});

Then.... the user needs to click the button, after which you can run this code.

btnAdd.addEventListener('click', (e) => {
  // hide our user interface that shows our A2HS button
  btnAdd.style.display = 'none';
  // Show the prompt
  deferredPrompt.prompt();
  // Wait for the user to respond to the prompt
  deferredPrompt.userChoice
    .then((choiceResult) => {
      if (choiceResult.outcome === 'accepted') {
        console.log('User accepted the A2HS prompt');
      } else {
        console.log('User dismissed the A2HS prompt');
      }
      deferredPrompt = null;
    });
});

I converted this to a react component fairly easily, the code below is cut down from my Redux project, so it will not work copy/paste, but should give the general idea.

import React, { Component } from 'react'
import Button from '@material-ui/core/Button'

class AddToHomeScreen extends Component {
  constructor (props) {
    super(props)
    this.deferredPrompt = null
    this.state = {
      show: false
    }
  }

  componentDidMount () {
    var component = this
    window.addEventListener('beforeinstallprompt', e => {
      // Prevent Chrome 67 and earlier from automatically showing the prompt
      e.preventDefault()
      // Stash the event so it can be triggered later.
      component.deferredPrompt = e
      // Show button
      console.log('beforeinstallprompt triggered... show add button')
      component.setState({ show: true })
    })
  }

  // bind to this
  handleAddClick () {
    if (this.deferredPrompt) {
      this.setState({ show: false })
      // Show the prompt
      this.deferredPrompt.prompt()
      // Wait for the user to respond to the prompt
      this.deferredPrompt.userChoice.then(choiceResult => {
        if (choiceResult.outcome === 'accepted') {
          console.log('User accepted the A2HS prompt')
        } else {
          console.log('User dismissed the A2HS prompt')
        }
        this.deferredPrompt = null
      })
    } else {
      console.log('Invalid prompt object')
    }
  }

  render () {
    const { show } = this.state
    if (!show) return null

    return (
      <div className={classes.root}>
        <Button variant="contained" onClick={this.handleAddClick.bind(this)}>
          Add to home screen
        </Button>
      </div>
    )
  }
}

export default AddToHomeScreen

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