我的PWA加载由head元素中的链接标签标识的匹配的iOS启动屏幕（通常做法）。因此，特定设备将始终仅使用这些PNG文件之一。
但是，无论屏幕大小是否匹配，我的serviceWorker都会将所有图像缓存在图像文件夹中。
sw.js ：
const staticAssets = [
'./',
'./styles.css',
'./app.js',
'./images',
'./fallback.json',
'./images/system/offline.png',
'sw.js'
]
self.addEventListener('install', async event => {
const cache = await caches.open('static-assets');
cache.addAll(staticAssets);
});
如果Android手机等正在保存PWA，我如何告诉我的服务人员仅缓存所需的启动屏幕，或者什么都不缓存？
从 index.html 头中提取：
<!-- iPhone Xs Max (1242px x 2688px) -->
<link rel="apple-touch-startup-image" media="(device-width: 414px) and (device-height: 896px) and (-webkit-device-pixel-ratio: 3)" href="images/splash/apple-launch-1242x2688.png">
<!-- iPhone Xr (828px x 1792px) -->
<link rel="apple-touch-startup-image" media="(device-width: 414px) and (device-height: 896px) and (-webkit-device-pixel-ratio: 2)" href="images/splash/apple-launch-828x1792.png">
<!-- iPhone X, Xs (1125px x 2436px) -->
<link rel="apple-touch-startup-image" media="(device-width: 375px) and (device-height: 812px) and (-webkit-device-pixel-ratio: 3)" href="images/splash/apple-launch-1125x2436.png">
<!-- iPhone 8 Plus, 7 Plus, 6s Plus, 6 Plus (1242px x 2208px) -->
<link rel="apple-touch-startup-image" media="(device-width: 414px) and (device-height: 736px) and (-webkit-device-pixel-ratio: 3)" href="images/splash/apple-launch-1242x2208.png">
<!-- iPhone 8, 7, 6s, 6 (750px x 1334px) -->
<link rel="apple-touch-startup-image" media="(device-width: 375px) and (device-height: 667px) and (-webkit-device-pixel-ratio: 2)" href="images/splash/apple-launch-750x1334.png">
<!-- iPhone 5s, SE (640px x 1136px)-->
<link rel="apple-touch-startup-image" media="(device-width: 320px) and (device-height: 568px) and (-webkit-device-pixel-ratio: 2)" href="images/splash/apple-launch-640x1136.png">
<!-- iPad Pro 12.9" (2048px x 2732px) -->
<link rel="apple-touch-startup-image" media="(device-width: 1024px) and (device-height: 1366px) and (-webkit-device-pixel-ratio: 2)" href="images/splash/apple-launch-2048x2732.png">
<!-- iPad Pro 11” (1668px x 2388px) -->
<link rel="apple-touch-startup-image" media="(device-width: 834px) and (device-height: 1194px) and (-webkit-device-pixel-ratio: 2)" href="images/splash/apple-launch-1668x2388.png">
<!-- iPad Pro 10.5" (1668px x 2224px) -->
<link rel="apple-touch-startup-image" media="(device-width: 834px) and (device-height: 1112px) and (-webkit-device-pixel-ratio: 2)" href="images/splash/apple-launch-1668x2224.png">
<!-- iPad Mini, Air (1536px x 2048px) -->
<link rel="apple-touch-startup-image" media="(device-width: 768px) and (device-height: 1024px) and (-webkit-device-pixel-ratio: 2)" href="images/splash/apple-launch-1536x2048.png">