uniApp跨页面通讯$on、$emit、$once、$off使用场景及技巧

大部分场景实际上利用$once、$emit、$off配合使用即可，直接上代码

在页面B中，离开时必须要销毁$once(xxx),因为在B页面，点击拍照才会触发$emit(xxx),如果通过滑动或点击头部返回页面A,$once(xxx)将会和下一次$emit(xxx)调用时，一起触发。

所以调用销毁方法$off(xxx)的实际很重要，onUnmounted配合nextTick使用，刚好不会影响上个页面A正常通过takePhoto 触发的事件

页面A

<template>
  <button @click="fn1">按钮1</button>
  <button @click="fn2">按钮2</button>
</template>

<script setup lang='ts'>
import { reactive, toRefs, onBeforeMount, onMounted } from 'vue'
const state = reactive({
  list1: [] as string[],
  list2: [] as string[]
})

const fn1 = () => {
  uni.navigateTo({ url: '页面B'})
  uni.$once('xxx', () => {
    // 监听后的逻辑
  })
}

const fn2 = () => {
  uni.navigateTo({ url: '页面B'})
  uni.$once('xxx', () => {
    // 监听后的逻辑
  })
}

</script>

<style lang="scss" scoped>

</style>

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页面B

<template>
  <my-header>点击可返回</my-header>
  <camera device-position="back" flash="off" style="width: 100%; height: 300px;"></camera>
  <button type="primary" @click="takePhoto">拍照</button>
</template>

<script setup lang='ts'>
import { reactive, toRefs, nextTick, onUnmounted } from 'vue'
const takePhoto = () => {
  const ctx = uni.createCameraContext();
  ctx.takePhoto({
    quality: 'high',
    success: (res) => {
      uni.$emit('xxx', res)
    }
  })
}

onUnmounted(() => {
  nextTick(() => {
    uni.$off('xxx')
    uni.navigateBack()
  })
})
</script>

<style lang="scss" scoped></style>
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