解决ElementUI组件中el-upload上传图片不显示问题

this.imageUrl = URL.createObjectURL(file);

<template>
	<div class="dashboard-container">
		<div class="dashboard-text">name: Upload 上传</div>
		<el-upload class="avatar-uploader" action="#" :show-file-list="false"
			 :before-upload="beforeAvatarUpload">
			<img v-if="imageUrl" :src="imageUrl" class="avatar">
			<i v-else class="el-icon-plus avatar-uploader-icon"></i>
		</el-upload>
	</div>
</template>

<script>
	export default {
		data() {
			return {
				imageUrl: ''
			}
		},
		methods: {
			beforeAvatarUpload(file) {
				console.log(file)
                // 使图片显示
				this.imageUrl = URL.createObjectURL(file);
				return false
			}
		}
	}
</script>

<style>
  .avatar-uploader .el-upload {
    border: 1px dashed #d9d9d9;
    border-radius: 6px;
    cursor: pointer;
    position: relative;
    overflow: hidden;
  }
  .avatar-uploader .el-upload:hover {
    border-color: #409EFF;
  }
  .avatar-uploader-icon {
    font-size: 28px;
    color: #8c939d;
    width: 178px;
    height: 178px;
    line-height: 178px;
    text-align: center;
  }
  .avatar {
    width: 178px;
    height: 178px;
    display: block;
  }
</style>

 <el-upload  action="#" accept="image/jpeg, image/jpg" ref="upload" :limit="1" :file-list.sync="fileList" :http-request="httpRequest" :on-success="handleAvatarSuccess" :before-upload="beforeAvatarUpload" :on-remove="removeFile">
              <el-button type="success" @click="handleBtnUpload()">上传</el-button>
</el-upload>