126.(前端)上传图片的预览

1.概述

当我们点击图片链接时，希望有一个弹窗能够显示图片，作为一个图片的预览

2.思路

我们先创建一个，让里面放一个的标签。给upload标签的属性:on-preview绑定一个函数，当点击链接时，就会发送一个图片的地址给到显示框。

3.代码展示

<template>
    <div>
        
        <el-breadcrumb separator-class="el-icon-arrow-right">
            <el-breadcrumb-item :to="{ path: '/home' }">首页el-breadcrumb-item>
            <el-breadcrumb-item>商品管理el-breadcrumb-item>
            <el-breadcrumb-item>增加商品el-breadcrumb-item>
        el-breadcrumb>
        <el-card>
            
            <el-alert title="增加商品信息" type="info" center show-icon>el-alert>
            
                <el-steps :active="active-0" finish-status="success" align-center>
                    
                    <el-step title="基本信息">el-step>
                    <el-step title="商品静态参数">el-step>
                    <el-step title="商品动态参数">el-step>
                    <el-step title="商品图片">el-step>
                    <el-step title="商品内容">el-step>
                    <el-step title="完成">el-step>
                el-steps>
            
            <el-form :model="addForm" ref="addRef" :rules="addRules" label-position="top">
                <el-tabs v-model="active" :tab-position="'left'" :before-leave="beforeLeave">
                    <el-tab-pane label="基本信息" name="0">
                        
                        <el-form-item label="商品名称" prop="name">
                            <el-input v-model="addForm.name">el-input>
                        el-form-item>
                        <el-form-item label="商品价格" prop="price">
                            <el-input v-model="addForm.price">el-input>
                        el-form-item>
                        <el-form-item label="商品数量" prop="number">
                            <el-input v-model="addForm.number">el-input>
                        el-form-item>
                        <el-form-item label="商品权重" prop="weight">
                            <el-input v-model="addForm.weight">el-input>
                        el-form-item>
                        <el-form-item label="商品分类">
                            <el-cascader v-model="selectKeys" :options="cateIdList"
                                :props="{ expandTrigger: 'hover', label:'name', value:'id', checkStrictly: true }"
                                @change="changeSeletor"
                                clearable
                                separator=">">
                            el-cascader>
                        el-form-item>
                    el-tab-pane>
                    <el-tab-pane label="商品静态参数" name="1">
                        
                        <el-form-item :label="s.name" v-for="s in attr_static" :key="s.id">
                            <el-input v-model="s.val">el-input>
                        el-form-item>
                    el-tab-pane>
                    <el-tab-pane label="商品动态参数" name="2">
                        <el-form-item :label="d.name" v-for="d in attr_dynamic" :key="d.id">
                            <el-checkbox-group v-model="d.val">
                                <el-checkbox :label="dv" v-for="(dv,i) in d.val" :key="i" border>el-checkbox>
                            el-checkbox-group>
                        el-form-item>
                    el-tab-pane>
                    <el-tab-pane label="商品图片" name="3">
                        <el-upload 
                        class="upload-demo" 
                        action="/api/upload_img" 
                        :on-preview="handlePreview"
                        :on-remove="handleRemove" 
                        :on-success="handleSuccess"
                        :file-list="fileList" 
                        list-type="picture">
                            <el-button size="small" type="primary">点击上传el-button>
                        el-upload>
                    el-tab-pane>
                    <el-tab-pane label="商品内容" name="4">商品内容el-tab-pane>
                el-tabs>
            el-form>
        el-card>
        <el-dialog title="图片预览" :visible.sync="previewVisible" width="40%">
            <img :src="previewPath" class="previewImg"/>
        el-dialog>
    div>
template>

<script>
export default {
    data() {
        return {
            active: '0',
            addForm:{
                'name':'',
                'price':0,
                'number':0,
                'weight':0,
                'cid_one':0,
                'cid_two':0,
                'cid_three':0,
                pics: []
            },
            addRules:{
                name:[{required:true, message:"请输入填写商品名称", tigger:'blur'}],
                price:[{required:true, message:"请输入填写商品价格", tigger:'blur'}],
                number:[{required:true, message:"请输入填写商品数量", tigger:'blur'}],
                weight:[{required:true, message:"请输入填写商品权重", tigger:'blur'}]
            },
            cateIdList:[],
            selectKeys:[],
            attr_static: [],
            attr_dynamic:[],
            previewVisible: false,
            previewPath: ''
        }
    },
    created() {
        this.getCateList()
    },
    methods: {
        // 获取全部列表，用于展示
        async getCateList() {
            const { data: resp } = await this.$axios.get('/api/category_list')
            if (resp.status !== 200) return this.$msg.error(resp.msg)
            this.cateIdList = resp.data.data
        },
        // 发生变更时
        changeSeletor() {
            if(this.selectKeys.length < 3) return
            this.addForm.cid_one = this.selectKeys[0]
            this.addForm.cid_two = this.selectKeys[1]
            this.addForm.cid_three = this.selectKeys[2]
            console.log(this.addForm);
        },
        // 验证是否能跳转到下一级tabs的函数
        beforeLeave(activeName, oldActiveName){
            // 验证是否存在三级目录的输入
            if(this.selectKeys.length < 3) {
                this.$msg.error("请先输入三级商品分类信息！！！！")
                return false
            }
            // console.log(activeName)
            // console.log(oldActiveName)
            // 在准备跳转到下一级时，发送请求获取到下一级静态的内容
            if (activeName === '1') this.getAttribute('static')
            if (activeName === '2') this.getAttribute('dynamic')
        },
        // 获取静态参数
        async getAttribute(_type) {
            const { data: resp } = await this.$axios.get('/api/category/attr_list', {
                params: { cid: this.selectKeys[2], _type: _type}
            })
            if (resp.status !== 200) return this.$msg.error(resp.msg)
            // console.log(resp.data);
            if (_type === 'static'){
                this.attr_static = resp.data
            }else{
                resp.data.forEach(item => {
                    item.val = item.val?item.val.split(','):[]
                })
                this.attr_dynamic = resp.data
            }
        },
        // 上传成功时触发：绑定上传图片的路径
        handleSuccess(resp){
            // console.log(resp); //查看返回值
            this.addForm.pics.push(resp.data.path)
        },
        // 删除上传图片
        handleRemove(file){
            // console.log(file);
            // console.log(this.addForm.pics);
            const i = this.addForm.pics.findIndex( x => x===file.response.data.path)
            this.addForm.pics.splice(i,1)
            // console.log(this.addForm.pics);
        },
        // 上传图片的预览
        handlePreview(file){
            this.previewVisible = true
            this.previewPath = file.response.data.url
        }
    }
}
script>

<style lang="less" scoped>
.el-tabs{
    margin-top: 10px
}
.el-alert{
    margin-bottom: 5px;
}
.el-cascader{
    width:500px
}
.el-checkbox{
    margin: 0 10px 0 0 !important;
}
.previewImg{
    width: 100%;
}
style>

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