参考：https://www.cnblogs.com/leisir/p/8392325.html
我的做法是在config.xml中加入

<preference name="AutoHideSplashScreen" value="false" />
<preference name="SplashShowOnlyFirstTime" value="false" />

然后在进入的首页的ts文件（tabs-page.ts）中加入

import { Platform } from '@ionic/angular';
import { SplashScreen } from '@ionic-native/splash-screen/ngx';
//...
  constructor(
    private platform: Platform,
    private splashScreen: SplashScreen,
  
) { }
//...
 ngOnInit() {

    this.platform.ready().then(() => {

      setTimeout(() => { 
        this.splashScreen.hide();
      }, 2000)
      
    });