我正在创建一个 angular2 项目，并使用 ng2-uploader 作为文件上传插件。我想拖放到一个 div 上，同时在 div 内添加一个上传按钮。选择要上传的文件后，我收到错误 TypeError：无法将未定义或 null 转换为对象 。

Html 代码为：

<div [hidden]="!onUpload" ngFileDrop [options]="options" (onUpload)="handleUpload($event)" [ngClass]="{'file-over': hasBaseDropZoneOver}" (onFileOver)="fileOverBase($event)">
     <input type="file" ngFileSelect [options]="options" (onUpload)="handleUpload($event)">
     <p><span>Response: {{ uploadFile | json }}</span></p>
</div>

组件为：

import { Component, OnInit, NgModule, NgZone } from '@angular/core';

@Component({
  selector: 'app-fileselect',
  templateUrl: './fileselect.component.html',
  styleUrls: ['./fileselect.component.css']
})

export class FileSelectComponent implements OnInit {
  zone: NgZone;
  hasBaseDropZoneOver: boolean = false;
  basicProgress: number = 0;
  uploadFile: any;

constructor() {
    this.zone = new NgZone({ enableLongStackTrace: false });//file upload    
  }

options: Object = {
    url: 'http://localhost:4200/assets/documents'
  };

handleUpload(data): void {
    if (data && data.response) {
      data = JSON.parse(data.response);
      this.uploadFile = data;
      this.zone.run(() => {
        this.basicProgress = data.progress.percent;
      });
    }
  } 

fileOverBase(e: any): void {
        this.hasBaseDropZoneOver = e;
      }
    }