Design and development techniques for UniApp to implement pull-down refresh and pull-up loading

UniApp is a cross-platform application framework developed based on the Vue.js framework. It can run on various platforms at the same time through a set of codes, including iOS, Android, H5, etc., which greatly improves development efficiency and code reusability. . In actual development, pull-down refresh and pull-up loading are common functional requirements. This article will introduce how UniApp implements this function and provide relevant design and development skills.

1. Implement pull-down refresh
Pull-down refresh means that after the user slides down a certain distance from the top of the page, it triggers the reloading of the page data. The following is a code example for UniApp to implement the pull-down refresh function:

<template>
  <view>
    <list v-model="listData" :finished="listFinished" @load="loadData"></list>
  </view>
</template>

<script>
  export default {
    data() {
      return {
        listData: [], // 列表数据
        listFinished: false // 列表是否加载完毕
      }
    },
    methods: {
      loadData() {
        // 模拟异步加载数据
        setTimeout(() => {
          this.listData = [/* 数据源 */]
          this.listFinished = true
        }, 1000)
      }
    }
  }
</script>

In the above code, we implement the pull-down refresh function through the <list></list> component. First, we defined listData in data to save the list data, and listFinished identifies whether the list has been loaded. In the loadData method, we simulate the process of asynchronously loading data. When the data is loaded, the data is assigned to listData, and listFinished is set to ##. #true.

2. Implement pull-up loading

Pull-up loading means that when the user slides to the bottom of the page, more data is automatically loaded. The following is a code example for UniApp to implement the pull-up loading function:

<template>
  <view>
    <list v-model="listData" :finished="listFinished" @load="loadMore"></list>
  </view>
</template>

<script>
  export default {
    data() {
      return {
        listData: [], // 列表数据
        listFinished: false // 列表是否加载完毕
      }
    },
    methods: {
      loadMore() {
        // 模拟异步加载更多数据
        setTimeout(() => {
          this.listData = this.listData.concat([/* 更多数据 */])
          this.listFinished = true
        }, 1000)
      }
    }
  }
</script>

In the above code, we also implement the pull-up loading function through the

component. Similar to pull-down refresh, simulate the process of asynchronously loading more data in the loadMore method, append the new data to listData, and set listFinished to true.

3. Other design and development skills

Use third-party libraries: UniApp can use many third-party plug-ins and libraries in the Vue.js ecosystem, such as "uni_ui", " vant"etc. These plug-ins often already provide pull-down refresh and pull-up loading components, which can be used directly to reduce development time and complexity.

1. <template>
     <view>
       <uni-load-more v-model="listData" :finished="listFinished" @load="loadData"></uni-load-more>
     </view>
   </template>
   
   <script>
     import { uniLoadMore } from 'uni_ui'
   
     export default {
       components: {
         uniLoadMore
       },
       data() {
         return {
           listData: [],
           listFinished: false
         }
       },
       methods: {
         loadData() {
           // 异步加载数据
         }
       }
     }
   </script>

Optimize performance: For large data lists, consider using paging loading to avoid page freezes caused by loading too much data at once. You can use the paginator component to listen for page scroll events and trigger loading more operations when scrolling to the bottom.

2. <template>
     <view>
       <list :data="listData" :finished="listFinished" @load="loadMore"></list>
       <view class="loading" v-show="loading">正在加载中...</view>
     </view>
   </template>
   
   <script>
     export default {
       data() {
         return {
           listData: [], 
           listFinished: false,
           loading: false, // 是否正在加载中
           page: 1, // 分页加载的当前页数
           pageSize: 10 // 分页加载的每页数量
         }
       },
       mounted() {
         // 监听页面滚动事件
         uni.$on('scroll', this.onScroll)
         // 初始化加载第一页数据
         this.loadData()
       },
       methods: {
         loadData() {
           this.loading = true
           // 模拟异步加载数据
           setTimeout(() => {
             // 加载数据成功后更新列表数据和标识
             this.listData = [/* 数据源 */]
             this.listFinished = true
             this.loading = false
           }, 1000)
         },
         loadMore() {
           // 当滚动到底部时加载更多数据
           this.page++
           this.loading = true
           // 模拟异步加载更多数据
           setTimeout(() => {
             // 加载数据成功后追加到列表数据中
             this.listData = this.listData.concat([/* 更多数据 */])
             this.loading = false
             // 判断是否加载完所有数据
             if (this.listData.length >= total) {
               this.listFinished = true
             }
           }, 1000)
         },
         onScroll(e) {
           // 判断是否滚动到页面底部
           if (e.scrollHeight - e.scrollTop - e.clientHeight <= 50) {
             this.loadMore()
           }
         }
       }
     }
   </script>

Summary:

Through the above code examples, we have introduced the related design and development techniques for implementing pull-down refresh and pull-up loading in UniApp. It can not only improve the user experience of the application, but also meet the user's real-time loading needs for data. I hope this article will help you implement this function in UniApp development.

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