使用upload组件，设置了mutiple模式，设置on-success , on-progress 并监听其回调
1，点击上传文件按钮
2，选择多个文件并上传
3，检测文件上传及成功时的回调

文件可以正常上传到服务器上，服务端上传接口也正确返回了200 ok，但是前端组件只接收到了一次on-success回调并正确处理，其他任务虽然成功，在回调的fileList中可以看到，percentage=100，但是showProgress始终为true，file.response也不存在。按说应该每个文件上传成功之后都应该触发回调

iview官方的issue如下：https://github.com/iview/ivie...

                <Upload
                    ref="upload"
                    :show-upload-list="false"
                    :on-success="handleSuccess"
                    :default-file-list="productImgList"
                    :format="['jpg','jpeg']"
                    :max-size="1024"
                    :on-format-error="handleFormatError"
                    :on-exceeded-size="handleMaxSize"
                    :before-upload="handleBeforeUpload"
                    multiple
                    type="drag"
                    :action="uploadUrl"
                    class="upload-comp"
                    v-show="productImgList.length < 6">
                <div class="upload-icon">
                </div>
            </Upload>
            
          handleSuccess (res, file, fileList) {
            let self = this;
            this.fileList = []
            if (Array.isArray(fileList)) {
                fileList.forEach((item) => {
                    this.fileList.push(item)
                })
            }
            this.fileList = fileList
            self.$nextTick(function(){
                self.$validator.validate('upload'+ self.index);
            });
        },

然后：

  watch: {
        fileList(newArr, oldArr) {
            console.log(JSON.stringify(oldArr))
            if (Array.isArray(newArr)) {
                for (let i = 0, len = newArr.length; i < len; i++) {
                    if (newArr[i].status === "finished"){
                        // console.log(newArr[i])
                        if (newArr[i].response && newArr[i].response.code === "success") {
                            this.productImgList.splice(i, 1, Object.assign({}, newArr[i], {
                                name: newArr[i].response.data,
                                url: global.IMG_URL + newArr[i].response.data,
                                fileName: newArr[i].response.data
                            }))
                        }
                    }
                }
            }
            // console.log(JSON.stringify( this.productImgList))
        }
    }

但是只监听到一次上传成功事件，请问怎么解决？