高级转换 / 动画 • Svelte Tutorial

高级 Svelte 高级转换动画

在上一章中，我们使用延迟转换来创建运动的幻觉，因为元素从一个待办事项列表移动到另一个待办事项列表。

¥In the previous chapter, we used deferred transitions to create the illusion of motion as elements move from one todo list to the other.

为了完成幻觉，我们还需要对未过渡的元素应用运动。为此，我们使用 animate 指令。

¥To complete the illusion, we also need to apply motion to the elements that aren’t transitioning. For this, we use the animate directive.

首先，将 flip 函数（flip 代表 ‘第一个、最后一个、反转、播放’）从 svelte/animate 导入到 TodoList.svelte：

¥First, import the flip function — flip stands for ‘First, Last, Invert, Play’ — from svelte/animate into TodoList.svelte:

TodoList

<script>
	import { flip } from 'svelte/animate';
	import { send, receive } from './transition.js';

	let { todos, remove } = $props();
</script>

<script lang="ts">
	import { flip } from 'svelte/animate';
	import { send, receive } from './transition.js';

	let { todos, remove } = $props();
</script>

然后将其添加到 <li> 元素中：

¥Then add it to the <li> elements:

TodoList

<li
	class={{ done: todo.done }}
	in:receive={{ key: todo.id }}
	out:send={{ key: todo.id }}
	animate:flip
>

在这种情况下，移动有点慢，所以我们可以添加一个 duration 参数：

¥The movement is a little slow in this case, so we can add a duration parameter:

TodoList

<li
	class={{ done: todo.done }}
	in:receive={{ key: todo.id }}
	out:send={{ key: todo.id }}
	animate:flip={{ duration: 200 }}
>

duration 也可以是 d => milliseconds 函数，其中 d 是元素必须行进的像素数

¥[!NOTE] duration can also be a d => milliseconds function, where d is the number of pixels the element has to travel

请注意，所有过渡和动画都是使用 CSS 而不是 JavaScript 应用的，这意味着它们不会阻止（或被）主线程阻止。

¥Note that all the transitions and animations are being applied with CSS, rather than JavaScript, meaning they won’t block (or be blocked by) the main thread.

延迟转换 setContext 和 getContext

<script>

	import TodoList from './TodoList.svelte';

	const todos = $state([

		{ id: 1, done: false, description: 'write some docs' },

		{ id: 2, done: false, description: 'start writing blog post' },

		{ id: 3, done: true, description: 'buy some milk' },

		{ id: 4, done: false, description: 'mow the lawn' },

		{ id: 5, done: false, description: 'feed the turtle' },

		{ id: 6, done: false, description: 'fix some bugs' }

]);

	let uid = todos.length + 1;

	function remove(todo) {

		const index = todos.indexOf(todo);

		todos.splice(index, 1);

</script>

<div class="board">

	<input

		placeholder="what needs to be done?"

		onkeydown={(e) => {

			if (e.key !== 'Enter') return;

			todos.push({

				id: uid++,

				done: false,

				description: e.currentTarget.value

});

			e.currentTarget.value = '';

}}

/>

	<div class="todo">

		<h2>todo</h2>

		<TodoList todos={todos.filter((t) => !t.done)} {remove} />

	</div>

	<div class="done">

		<h2>done</h2>

		<TodoList todos={todos.filter((t) => t.done)} {remove} />

	</div>

</div>

<style>

	.board {

		display: grid;

		grid-template-columns: 1fr 1fr;

		grid-column-gap: 1em;

		max-width: 36em;

		margin: 0 auto;

	.board > input {

		font-size: 1.4em;

		grid-column: 1/3;

		padding: 0.5em;

		margin: 0 0 1rem 0;

	h2 {

		font-size: 2em;

		font-weight: 200;

</style>

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