elementUI上传多张图片回显在编辑( file-list )

结构:
<el-form-item style="width: 730px;">
    <span slot="label"><b style="color:#fff">*</b>头像</span>
        <el-upload
              :action="actionPath"
              list-type="picture-card"
              :on-remove="handleRemove"
              :on-change="handleChange"
              :data="postData"
              :on-success="handleAvatarSuccess"
              :before-upload="beforeAvatarUpload"
              :file-list="photoList"
              :class="{ hide: hideUpload }"
         >
         <i class="el-icon-plus"></i>
        </el-upload>
        <el-dialog :visible.sync="formCustom.dialogVisible" style="margin-left:20px">
           <img width="100%" :src="formCustom.headPortrait"  />
        </el-dialog>
</el-form-item>

data:
actionPath: "https://upload.qiniup.com", //上传到服务器的路径
postData: { token:"生成的token" },
photoList: [],
headPortrait:[]//传给后端

    // 显示对应数据
    lookList() {
      const req = {id: this.$route.query.id};
      gymnasiumLookVue(req).then(res => {
        if (res.data.code == "200") {
          this.introductionListLook = res.data.data.rows;
          this.list = this.introductionListLook.map(item => {
            const _this = this.formCustom;
            // 回显图片 file-list的值是数组，数组中要有url属性存放图片路径
            item.poster.map(itemImg => {
              let imageUrl = itemImg;
              this.photoList.push({
                url: imageUrl
              });
              this.formCustom.headPortrait = [];
              for (let i = 0; i < this.photoList.length; i++) {
                if (this.photoList[i].url) {
              //将已有的图片push到传给后端的数组中并初始化
            this.formCustom.headPortrait.push(this.photoList[i].url);
                }
              }
              // 回显时如果图片 >=8张隐藏上传按钮
              if (this.photoList.length >= 8) {
                this.hideUpload = true;
              } else {
                this.hideUpload = false;
              }
            });
          });
        } else {
          return false;
        }
      });
    }        

上传成功回调：
handleAvatarSuccess(res) {
      var qiHttp = "https://model.bunnyfit.cn/";
     //拿到所有图片
      this.formCustom.headPortrait.push(qiHttp + res.key);
},

change事件
handleChange(fileList) {
      //如果图片大于等于8张，隐藏上传按钮
      if (this.formCustom.headPortrait.length >= 8) {
        this.hideUpload = true;
      }
}

删除成功的回调
handleRemove(file, fileList) {
     //显示上传按钮
      if (this.formCustom.headPortrait.length <= 8) {
        this.hideUpload = false;
      }
      //删除已经选中的对应图片
      let currentIdIndex = this.formCustom.headPortrait.findIndex(
        item => item == file.url
      );
      if (currentIdIndex != -1) {
        this.formCustom.headPortrait.splice(currentIdIndex, 1);
      }
}