Implementation process of pull-down refresh function in Vue documentation

Vue is a popular JavaScript framework that provides an efficient way to create dynamic user interfaces. In the Vue documentation, there is a very useful function, the pull-down refresh function, which allows users to refresh the page when pulling down. This article will introduce the implementation process of this function.

To implement pull-down refresh, you need to use two Vue instructions: v-on and v-bind. The v-on directive is used to bind events, and the v-bind directive is used to bind attributes.

First, you need to define the data object in the main Vue instance to save the status of the components on the page that need to be refreshed:

data: {
  refreshFlag: false,
  startY: 0,
  moveY: 0,
  endY: 0
}

Four variables are defined here: refreshFlag indicates whether it is refreshing Status, startY, moveY and endY are used to record the location information of the user's pull-down.

Next, bind the v-on and v-bind instructions to the component that needs to be refreshed. The v-on directive is used to bind touchstart, touchmove and touchend events, and the v-bind directive is used to bind style classes. The specific code is as follows:

<div class="scroll" ref="scroll" v-bind:class="{active: refreshFlag}" v-on:touchstart="handleTouchStart" v-on:touchmove="handleTouchMove" v-on:touchend="handleTouchEnd">
  <!-- 列表内容 -->
</div>

The ref attribute is used here to obtain the DOM object of the scroll element to facilitate subsequent operations.

Next, you need to write three event processing functions, corresponding to touchstart, touchmove and touchend events respectively. In these functions, you need to change the variables in the data object and update the style class. The specific code is as follows:

handleTouchStart(event) {
  if (this.refreshFlag) {
    return;
  }
  this.startY = event.touches[0].pageY;
},
handleTouchMove(event) {
  if (this.refreshFlag) {
    return;
  }
  this.moveY = event.touches[0].pageY - this.startY;
  if (this.moveY > 0 && this.moveY < 40) {
    event.preventDefault();
  }
  if (this.moveY >= 40) {
    this.refreshFlag = true;
  }
},
handleTouchEnd(event) {
  if (this.moveY >= 40) {
    this.refreshFlag = false;
    this.$emit('refresh');
  }
  this.moveY = 0;
}

In the touchstart event processing function, record the position when the user clicks on the screen and prepare for subsequent calculation of the moveY value.

In the touchmove event processing function, based on the distance moved by the user's finger, determine whether it is at the pull-down refresh threshold. If it is reached, set refreshFlag to true. In addition, you need to use the preventDefault() method to prevent the default scroll event.

In the touchend event processing function, determine whether the refresh threshold is reached. If so, trigger a refresh event, set refreshFlag to false, and reset moveY to 0.

The complete code is as follows:

<template>
  <div>
    <div class="scroll" ref="scroll" v-bind:class="{active: refreshFlag}" v-on:touchstart="handleTouchStart" v-on:touchmove="handleTouchMove" v-on:touchend="handleTouchEnd">
      <!-- 列表内容 -->
    </div>
  </div>
</template>

<script>
  export default {
    data: {
      refreshFlag: false,
      startY: 0,
      moveY: 0,
      endY: 0
    },
    methods: {
      handleTouchStart(event) {
        if (this.refreshFlag) {
          return;
        }
        this.startY = event.touches[0].pageY;
      },
      handleTouchMove(event) {
        if (this.refreshFlag) {
          return;
        }
        this.moveY = event.touches[0].pageY - this.startY;
        if (this.moveY > 0 && this.moveY < 40) {
          event.preventDefault();
        }
        if (this.moveY >= 40) {
          this.refreshFlag = true;
        }
      },
      handleTouchEnd(event) {
        if (this.moveY >= 40) {
          this.refreshFlag = false;
          this.$emit('refresh');
        }
        this.moveY = 0;
      }
    }
  }
</script>

<style scoped>
  .scroll {
    height: 300px;
    overflow: scroll;
    position: relative;
  }
  .active {
    position: relative;
    top: 40px;
  }
</style>

Note that a refresh event is triggered in the code. This event can be bound to a processing function in the parent component for reacquisition and rendering of data. For example, you can write this in the parent component:

<template>
  <div>
    <MyComponent v-on:refresh="refreshData" />
  </div>
</template>

<script>
  export default {
    methods: {
      refreshData() {
        // 重新获取数据
        // 更新UI
      }
    }
  }
</script>

In short, through the above method, you can implement the pull-down refresh function in Vue. This feature is not only very useful for some mobile web applications, but can also play a role in improving user experience in desktop web applications.

The above is the detailed content of Implementation process of pull-down refresh function in Vue documentation. For more information, please follow other related articles on the PHP Chinese website!