youxi-app/uni_modules/cool-ui/components/cl-back-top/cl-back-top.uvue

<template>
	<view class="cl-back-top-wrapper" :style="{ bottom }" @tap="toTop">
		<view
			class="cl-back-top"
			:class="{
				'is-show': visible
			}"
		>
			<cl-icon name="skip-up-line" color="white" size="25px"></cl-icon>
		</view>
	</view>
</template>

<script setup lang="ts">
import { getTabBarHeight, hasCustomTabBar, scroller } from "@/cool";
import { computed, onMounted, onUnmounted, ref, watch, type PropType } from "vue";
import { usePage } from "../../hooks";
import { clFooterOffset } from "../cl-footer/offset";

defineOptions({
	name: "cl-back-top"
});

const props = defineProps({
	top: {
		type: Number as PropType<number | null>,
		default: null
	}
});

const emit = defineEmits(["backTop"]);

const { screenHeight } = uni.getWindowInfo();

// cl-page 上下文
const { scrollToTop, onScroll, offScroll } = usePage();

// 是否显示回到顶部按钮
const visible = ref(false);

// 底部距离
const bottom = computed(() => {
	let h = 20;

	if (hasCustomTabBar()) {
		h += getTabBarHeight();
	} else {
		h += clFooterOffset.get();
	}

	return h + "px";
});

// 是否页面滚动
const isPage = computed(() => props.top == null);

// 控制是否显示
function onVisible(top: number) {
	visible.value = top > screenHeight - 100;
}

// 回到顶部
function toTop() {
	if (isPage.value) {
		scrollToTop();
	}

	emit("backTop");
}

onMounted(() => {
	if (isPage.value) {
		// 监听页面滚动
		onScroll(onVisible);
	} else {
		// 监听参数变化
		watch(
			computed(() => props.top!),
			(top: number) => {
				onVisible(top);
			},
			{
				immediate: true
			}
		);
	}
});

onUnmounted(() => {
	if (isPage.value) {
		offScroll(onVisible);
	}
});
</script>

<style lang="scss" scoped>
.cl-back-top {
	@apply flex flex-row items-center justify-center bg-primary-500 rounded-full duration-300;
	width: 40px;
	height: 40px;
	transition-property: transform;
	transform: translateX(160rpx);

	&.is-show {
		transform: translateX(-20px);
	}

	&-wrapper {
		@apply fixed right-0 z-50 overflow-visible;
	}
}
</style>