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UI Virtualization

UI virtualization loads only viewable list items in a view port, which will improve the ListView performance while loading a large number of data.

Module injection

In order to use UI Virtualization, virtualization module should be injected into the provide section and use listview as a key of the object.

export default {
  data: function() {
    return {
      listData: listData,
      enableUi: true
    };
  },
  provide: {
    listview: [Virtualization]
  }
}

Getting started

UI virtualization can be enabled in the ListView by setting the enableVirtualization property to true.

It has two types of scrollers as follows:

Window scroll: This scroller is used in the ListView by default.

Container scroll: This scroller is used, when the height property of the ListView is set.

Source
Preview
app.vue
<template>
  <div class="control-section">
     <ejs-listview id='ui-list' :dataSource='listData' :enableVirtualization='enableUi' >
    </ejs-listview>
  </div>
</template>
<style>
#app {
    color: #008cff;
    height: 40px;
    left: 30%;
    position: absolute;
}

#ui-list {
  display: block;
  max-width: 400px;
  margin: auto;
  border-radius: 3px;
  cursor: pointer;
}
</style>
<script>
import Vue from "vue";
import { ListViewPlugin, Virtualization } from "@syncfusion/ej2-vue-lists";
Vue.use(ListViewPlugin);
let listData = [];

export default {
  beforeCreate: function() {
    listData = [
      { text: "Nancy", id: "0" },
      { text: "Andrew", id: "1" },
      { text: "Janet", id: "2" },
      { text: "Margaret", id: "3" },
      { text: "Steven", id: "4" },
      { text: "Laura", id: "5" },
      { text: "Robert", id: "6" },
      { text: "Michael", id: "7" },
      { text: "Albert", id: "8" },
      { text: "Nolan", id: "9" }
    ];

    for (let i = 10; i <= 1000; i++) {
      let index = parseInt((Math.random() * 10).toString());
      listData.push({ text: listData[index].text, id: i.toString() });
    }
  },
  data: function() {
    return {
      listData: listData,
      enableUi: true
    };
  },
  provide: {
    listview: [Virtualization]
  }
};
</script>

Template

We can use template property to customize list items in UI virtualization.

Source
Preview
app.vue
<template>
  <div class="control-section">
     <ejs-listview id='ui-list' :dataSource='listData' :enableVirtualization='enableUi' :showHeader='header' :fields='fields' :headerTitle='title' :template='gTemplate' :height='height' >
    </ejs-listview>
  </div>
</template>
<style>
#app {
    color: #008cff;
    height: 40px;
    left: 30%;
    position: absolute;
}

#ui-list {
    display: block;
    max-width: 400px;
    margin: auto;
    border: 1px solid #dddddd;
    border-radius: 3px;
    cursor: pointer;
}

button {
    float: right
}

#icon {
    width: 45px;
    height: 45px;
    text-align: center;
    line-height: 45px;
    border-radius: 50%;
    font-size: 20px;
    font-weight: 500;
    float: left;
    margin-top: 17px;
    margin-right: 35px;
}

img {
    border-radius: 50%;
    border: #ddd;
    border: 1px solid rgba(40, 40, 40, 0.12);
}

.R {
    background: purple;
}

.M {
    background: pink;
}

.A {
    background: green;
}

.S {
    background: lightskyblue;
}

.J {
    background: orange;
}

.N {
    background: blue;
}

#ui-list .e-list-item {
    height: 80px;
    border: #ddd;
    border: 1px solid rgba(184, 184, 184, 0.12);
}

.list-container {
    width: inherit;
    height: 100%;

}

.showUI {
    display: inline;
}

.hideUI {
    display: none;
}

.content {
    height: 100%;
    float: left;
}

.name {
    height: 100%;
    font-size: 20px;
    font-weight: 600;
    line-height: 78px;
}

</style>
<script>
import Vue from "vue";
import { ListViewPlugin, Virtualization } from "@syncfusion/ej2-vue-lists";
Vue.use(ListViewPlugin);
let listData = [];

export default {
    beforeCreate: function() {
listData = [
    { name: 'Nancy', icon: 'N', id: '0', },
    { name: 'Andrew', icon: 'A', id: '1' },
    { name: 'Janet', icon: 'J', id: '2' },
    { name: 'Margaret', imgUrl: './margaret.png', id: '3' },
    { name: 'Steven', icon: 'S', id: '4' },
    { name: 'Laura', imgUrl: './laura.png', id: '5' },
    { name: 'Robert', icon: 'R', id: '6' },
    { name: 'Michael', icon: 'M', id: '7' },
    { name: 'Albert', imgUrl: './albert.png', id: '8' },
    { name: 'Nolan', icon: 'N', id: '9' }
];

for (let i = 10; i <= 1000; i++) {
    let index = parseInt((Math.random() * 10).toString());
    listData.push({ name: listData[index].name, icon: listData[index].icon, imgUrl: listData[index].imgUrl, id: i.toString() });
}
},
  data: function() {
    return {
      listData: listData,
      gTemplate:
        '<div class="list-container"><div id="icon" class="${$imgUrl ? \'img\' : $icon }">' +
        "<span class=\"${$imgUrl ? 'hideUI' : 'showUI' }\">" +
        "${icon}</span> <img class=\"${$imgUrl ? 'showUI' : 'hideUI' }\" width = 45 height = 45 src=\"${$imgUrl ?  $imgUrl : ' ' }\" />" +
        '</div><div class="name">${name}</div></div>',
      header: true,
      title: "Contacts",
      fields: { text: "name" },
      height: 500,
      enableUi: true,
    };
  },
  provide: {
    listview: [Virtualization]
  }
}
</script>

Conditional rendering

The following conditional rendering support is provided for the template and groupTemplate.

Name Syntax
conditional class <div class="${ $id % 2 === 0 ? 'even-list' : 'odd-list'}"></div>
conditional attribute <div id="${ $id % 2 === 0 ? 'even-list' : 'odd-list'}"></div>
conditional text content <div>${ $id % 2 === 0 ? 'even-list' : 'odd-list'}</div>

In the following sample, the light blue is applied for the even list and light coral is applied for the odd list based on the conditional class.

Source
Preview
app.vue
<template>
  <div class="control-section">
     <ejs-listview id='ui-list' :dataSource='listData' :enableVirtualization='enableUi'  :template='gTemplate' :height='height' >
    </ejs-listview>
  </div>
</template>
<style>
#app {
    color: #008cff;
    height: 40px;
    left: 30%;
    position: absolute;
}

#ui-list {
    display: block;
    max-width: 400px;
    margin: auto;
    border: 1px solid #dddddd;
    border-radius: 3px;
    cursor: pointer;
}

#list-container{
    height: inherit;
    width: inherit;
    padding-left: 30px;
}

#ui-list .e-list-item{
    padding: 0;
}

#ui-list .even-list{
  background-color: lightblue;
}

#ui-list .odd-list{
  background-color: lightcoral;
}

</style>
<script>
import Vue from "vue";
import { ListViewPlugin, Virtualization } from "@syncfusion/ej2-vue-lists";
Vue.use(ListViewPlugin);
let listData = [];

export default {
  beforeCreate: function() {
listData = [
    { text: 'Nancy', id: '0', },
    { text: 'Andrew', id: '1' },
    { text: 'Janet', id: '2' },
    { text: 'Margaret', id: '3' },
    { text: 'Steven', id: '4' },
    { text: 'Laura', id: '5' },
    { text: 'Robert', id: '6' },
    { text: 'Michael', id: '7' },
    { text: 'Albert', id: '8' },
    { text: 'Nolan', id: '9' }
];

for (let i = 10; i <= 1000; i++) {
    let index = parseInt((Math.random() * 10).toString());
    listData.push({ text: listData[index].text, id: i.toString() });
}
},
  data: function() {
    return {
      listData: listData,
      gTemplate:  '<div id="list-container" class="${ $id % 2 === 0 ? \'even-list\' : \'odd-list\' }" > ${text} </div>',
      height: 500,
      enableUi: true,
    };
  },
  provide: {
    listview: [Virtualization]
  }
}
</script>