Svelte transition in __layout - transition

Question

How can use transitions in __layout for loading a page with animation?
__layout.svelte :
<script>
import Header from '$lib/Header/index.svelte'
import Footer from '$lib/Footer/index.svelte'
import '../../app.css'
import Animate from '$lib/Animate.svelte'
</script>
<Header />
<div class="bg-gray-100">
<div class="container mx-auto px-4 sm:px-6 lg:px-8">
<Animate>
<slot />
</Animate>
</div>
</div>
<Footer />
Animate.svelte :
<script>
import { fade, fly } from 'svelte/transition'
</script>
<div in:fly={{ y: 200, duration: 2000 }} out:fade>
<slot />
</div>
in this example transitioning effects only works for one time and shows animation. but I'd like to show transition every time that page changes!
Is there a solution to improve this app?

Answer 1

For this you need to use the {#key} block in combination with some variable that updates when you want it to. You can use page from $app/stores for that.
__layout.svelte:
<script>
import Header from '$lib/Header/index.svelte'
import Footer from '$lib/Footer/index.svelte'
import '../../app.css'
import Animate from '$lib/Animate.svelte'
import { page } from '$app/stores' // <-- new
</script>
<Header />
<div class="bg-gray-100">
<div class="container mx-auto px-4 sm:px-6 lg:px-8">
<!-- The key's content is destroyed and recreated everytime the $page
variable changes -->
{#key $page}
<Animate>
<slot />
</Animate>
{/key}
</div>
</div>
<Footer />
Docs for $app/stores: https://kit.svelte.dev/docs#modules-$app-stores
Docs for {#key}: https://svelte.dev/docs#key