本来lightning-datatable这种标签，基本上任何的项目都会用到而且很精通，所以当时感觉没有太大的单独一篇写的必要，在Salesforce LWC学习(三十) lwc superbadge项目实现 中也有使用这个标签的demo，所以有类似需要的小伙伴参考一下也可以照猫画虎搞定需求。项目中遇见了两个datatable的问题，解决以后感觉有必要写一下，后期遇见这种坑的小伙伴可以快速对应。话不多说，先弄一个简单的分页效果的UI，UI很丑，旨在实现功能。
AccountListController.cls：一个简单的搜索list返回
public without sharing class AccountListController {
public static final Integer DEFAULT_PAGE_SIZE = 100;
@AuraEnabled(cacheable=false)
public static List<Account> fetchAccountList(String serializedAccount){
Account account = (Account)JSON.deserialize(serializedAccount,Account.class);
String fetchAccountSQL = 'SELECT Id,Name,Industry,AccountSource,Owner.Name FROM Account WHERE IsDeleted = false ';
if(String.isNotBlank(account.name)) {
fetchAccountSQL += 'AND Name like' + '\'%' + account.name + '%\'';
}
if(String.isNotBlank(account.industry)) {
fetchAccountSQL += ' AND industry = \'' + account.industry + '\'';
}
if(String.isNotBlank(account.AccountSource)) {
fetchAccountSQL += ' AND AccountSource = \'' + account.AccountSource + '\'';
}
Integer accountSize = DEFAULT_PAGE_SIZE;
fetchAccountSQL += ' LIMIT ' + accountSize;
List<Account> accountList = Database.query(fetchAccountSQL);
return accountList;
}
}
accountSearchForm.html
<template>
<!--use LDS to bind account -->
<lightning-record-edit-form
object-api-name='Account'
onsubmit={handleRecordFormSubmit}
>
<!--used to show section close/open-->
<lightning-accordion allow-multiple-sections-open
active-section-name={activeSections}> <lightning-accordion-section name="basic" label="basic">
<lightning-layout multiple-rows="true">
<lightning-layout-item padding="around-small" flexibility='auto' size='4'>
<lightning-input-field field-name='Name'></lightning-input-field>
</lightning-layout-item> <lightning-layout-item padding="around-small" flexibility='auto' size='4'>
<lightning-input-field field-name="AccountSource"></lightning-input-field>
</lightning-layout-item> <lightning-layout-item padding="around-small" flexibility='auto' size='4'>
<lightning-input-field field-name="Industry"></lightning-input-field>
</lightning-layout-item>
</lightning-layout>
</lightning-accordion-section>
</lightning-accordion> <!-- button group area -->
<lightning-layout horizontal-align="center">
<lightning-layout-item >
<lightning-button variant="brand" label="search" type="submit" name="search"></lightning-button>
</lightning-layout-item>
</lightning-layout>
</lightning-record-edit-form>
</template>
accountSearchForm.js
import { LightningElement,track } from 'lwc';
export default class AccountSearchForm extends LightningElement {
@track activeSections = ['basic'];
@track account;
handleRecordFormSubmit(event) {
event.preventDefault();
this.account = event.detail;
this.dispatchEvent(new CustomEvent('searchaccount',{detail:this.account}));
}
}
myAccountList.html
<template>
<lightning-card title="list for account data" icon-name="standard:account">
<div style="height: 150px;">
<lightning-datatable
data={accountListForCurrentPage}
columns={columns}
show-row-number-column
key-field="id">
</lightning-datatable>
</div> <lightning-layout horizontal-align="center">
<lightning-layout-item flexibility='auto' size='1'>
<lightning-combobox
value={perSize}
options={entryList}
placeholder="choose size"
onchange={handlePerSizeChange} > </lightning-combobox>
</lightning-layout-item>
<lightning-layout-item flexibility='auto' size='9' class="slds-text-align_center">
totalSize: {totalSize}
</lightning-layout-item>
<lightning-layout-item flexibility="auto" size="2">
<lightning-button variant="brand" label="<--" disabled={isFirstPage} onclick={handlePreviousPageClick}></lightning-button>
<lightning-button variant="brand" label="-->" disabled={isLastPage} title="next" onclick={handleNextPageClick}></lightning-button>
</lightning-layout-item>
</lightning-layout>
</lightning-card>
</template>
myAccountList.js
import { LightningElement,api, track } from 'lwc';
const columns = [
{label: 'Account Name', fieldName: 'Name'},
{label: 'Account Industry', fieldName: 'Industry'},
{label: 'Account Source', fieldName: 'AccountSource'},
{label: 'Owner Name', fieldName: 'OwnerName'}
];
export default class MyAccountList extends LightningElement {
//searched account list used to show in component table
@api accountList;
//indicator if table header checkbox check or not, true for check
@api totalChecked;
//list total entryList
@api totalSize;
//per size for show in table
@api perSize;
//current page index
@api currentPageIndex;
//list show in table
@api accountListForCurrentPage;
//indicator if current page is first page
@api isFirstPage;
//indicator if current page is last page
@api isLastPage;
@track columns = columns;
get entryList() {
return [
{ label: '3', value: '3' },
{ label: '5', value: '5' },
{ label: '10', value: '10' },
];
}
/**
* description: item checkbox check/uncheck, dispatch itemcheck custom event and parent component handle this
* @param event system event,used to get which item check/uncheck
*/
handleItemCheckboxClick(event) {
this.dispatchEvent(new CustomEvent('itemcheck',{detail:{id:event.currentTarget.value,checked:event.currentTarget.checked}}));
}
/**
* description: table header checkbox check/check, dispatch allcheck custom event
* @param event system event, used to get if table header checkbox check/uncheck
*/
handleAllCheckboxClick(event) {
this.dispatchEvent(new CustomEvent('allcheck',{detail:{checked:event.currentTarget.checked}}));
}
handleNextPageClick() {
this.dispatchEvent(new CustomEvent('nextpage'));
}
handlePreviousPageClick() {
this.dispatchEvent(new CustomEvent('previouspage'));
}
handlePerSizeChange(event) {
let currentSize = event.detail.value;
this.dispatchEvent(new CustomEvent('persizechange',{detail:{currentSize:currentSize}}));
}
}
accountListContainer.html
<template>
<c-account-search-form onsearchaccount={handleSearchAccountEvent}></c-account-search-form>
<c-my-account-list is-first-page={isFirstPage} is-last-page={isLastPage} account-list={accountList} account-list-for-current-page={accountListForCurrentPage} total-checked={totalChecked} onitemcheck={handleItemCheckEvent} onallcheck={handleAllCheckedEvent} onnextpage={handleNextPageEvent} onpreviouspage={handlePreviousPageEvent} total-size={totalSize} per-size={perSize} onpersizechange={handlePerSizeChangeEvent}></c-my-account-list> </template>
accountListContainer.js
import { LightningElement,track } from 'lwc';
import fetchAccountList from '@salesforce/apex/AccountListController.fetchAccountList';
export default class AccountListContainer extends LightningElement {
//account list used to show in account table
@track accountList = [];
//account form used to store form information user searched
@track accountForm;
//errors when fetch account list error
@track errors;
//indicator if table header total check box checked or not, true means checked
@track totalChecked = false;
//indicator if list modal close
@track showSelectedListModal = false;
@track data = [];
//list total size
@track totalSize;
//per size for show in table
@track perSize = 5;
//current page index
@track currentPageIndex;
//list show in table
@track accountListForCurrentPage;
@track isFirstPage = true;
@track isLastPage = true;
/**
* description: search account data by form information and set the result to account list to show in table
* @param event system event used to get form detail information
*/
handleSearchAccountEvent(event) {
this.totalChecked = false;
this.accountForm = event.detail;
fetchAccountList({serializedAccount:JSON.stringify(event.detail)})
.then(result => {
this.accountList = result;
this.totalSize = result.length;
this.currentPageIndex = 1;
if(this.totalSize > this.perSize * this.currentPageIndex) {
this.setPagination();
} else {
this.accountListForCurrentPage = this.accountList;
this.accountListForCurrentPage.forEach(item => {
if(item.Owner) {
item.OwnerName = item.Owner.Name;
}
});
this.isLastPage = true;
}
this.errors = undefined;
})
.catch(error =>{
this.errors = error;
this.accountList = undefined;
});
}
handlePreviousPageEvent() {
this.currentPageIndex = this.currentPageIndex - 1;
this.setPagination();
}
handlePerSizeChangeEvent(event) {
this.perSize = event.detail.currentSize;
this.currentPageIndex = 1;
this.setPagination();
}
handleNextPageEvent() {
this.currentPageIndex = this.currentPageIndex + 1;
this.setPagination();
}
setPagination() {
this.accountListForCurrentPage = [];
let tmpList = [];
for(let index = (this.perSize * (this.currentPageIndex - 1)); index < this.totalSize; index++) {
if(index < this.perSize * this.currentPageIndex) {
if(this.accountList[index].Owner) {
this.accountList[index].OwnerName = this.accountList[index].Owner.Name;
}
tmpList.push(this.accountList[index]);
}
}
this.accountListForCurrentPage = tmpList;
if(this.currentPageIndex === 1) {
this.isFirstPage = true;
} else {
this.isFirstPage = false;
}
if(this.perSize * this.currentPageIndex >= this.totalSize) {
this.isLastPage = true;
} else {
this.isLastPage = false;
}
}
}
结果展示：
看上去还可以是吧，但是有两个潜在的问题。
按照以下操作步骤，第一页有拖动条，选择了第5条数据
点击翻页以后，两个问题如下：
1）第二页的第五条同样的默认勾选了，尽管这个时候我们如果使用event.detail.selectedRows去获取选中的选项，第二页是没有在这里的，但是UI撒谎了，这个是一个很严重的bug；
2）第二页进去以后，滚动条没有在最上面，即没有默认展示第一条数据。
这两个问题，第二个问题是小问题，可以忍；第一个问题会让用户有concern，属于很严重的问题。但是什么原因呢？？？其实我也不太清楚是什么原因，datatable官方的设计中也没有翻页的demo，大部分都是loadMore当页增加数据场景，所以可能针对每页的index处选中效果有某个隐藏的bug。当我们尽管更新了list的数据，但是index给渲染了，很容易是render层的bug。所以我们想一下如何去处理这种问题。既然同步的渲染有问题，我们考虑其他方式，setTimeout弄成异步调用或者改成Promise实现。优化后的方案如下所示：
myAccountList.js新增一个方法
@api handleTableScrollTop() {
this.template.querySelector('div').scrollTop = 0;
}
accountListContainer.js修改一下 setPagination方法。新增了 setList这个Promise，js执行顺序 ： 同步代码 > Promise > setTimeout这种异步方式。
setPagination() {
this.accountListForCurrentPage = [];
let tmpList = [];
for(let index = (this.perSize * (this.currentPageIndex - 1)); index < this.totalSize; index++) {
if(index < this.perSize * this.currentPageIndex) {
if(this.accountList[index].Owner) {
this.accountList[index].OwnerName = this.accountList[index].Owner.Name;
}
tmpList.push(this.accountList[index]);
}
}
//this.accountListForCurrentPage = tmpList;
if(this.currentPageIndex === 1) {
this.isFirstPage = true;
} else {
this.isFirstPage = false;
}
if(this.perSize * this.currentPageIndex >= this.totalSize) {
this.isLastPage = true;
} else {
this.isLastPage = false;
}
const setList = () =>
new Promise((resolve, reject) => {
resolve(tmpList);
});
setList()
.then((result) => {
this.accountListForCurrentPage = tmpList;
this.template.querySelector('c-my-account-list').handleTableScrollTop();
});
}
通过以上的代码就可以解决上述的两个问题了。原理的话因为不清楚 datatable的渲染方式，只能找到解决这种问题的workaround的方式，同时作为sf开发人员在开发lightning的过程中，javascript真的是越来越重要了！！！
总结：篇中代码实现了通过 lightning-datatable翻页效果以及针对两个潜在的bug的修复。偏中有错误欢迎指出，有不懂欢迎留言。有更好方式欢迎交流。
