在Angular 4中使用html2canvas

Question

我能够在Angular 4中使用html2canvas进行截图，但我需要通过HTTP POST调用将字符串图像发送到服务器端。

组件

import { Component, OnInit, NgZone } from '@angular/core';
import { Router, ActivatedRoute, Params } from '@angular/router';
import { EventsEmitter } from '../../assets/scripts/services/eventsEmitter';
import { WindowRef } from '../../assets/scripts/services/window';
import { ImagesService } from '../images/images.component.service';
import { DomSanitizer } from '@angular/platform-browser';
import * as html2canvas from "html2canvas";


@Component({
    selector: 'categories',
    templateUrl: 'app/components/view/view.component.html',
    styleUrls: ['app/components/view/view.component.css'],
    providers: [ImagesService]
})
export class ViewComponent {
    
   

    constructor(
        private route: ActivatedRoute,
        private router: Router,
        private imagesService: ImagesService,
        private eventsEmitter: EventsEmitter
        private sanitizer: DomSanitizer,
        private window: WindowRef) {
        this.window.nativeWindow.scrollTo(0, 0);
    }

    ngOnInit() {
    }

    pdfDownload() {
        html2canvas(document.body).then(function (canvas) {
            var imgData = canvas.toDataURL("image/png");
            document.body.appendChild(canvas);
        });
    }


    AddImagesResource(query: any) {
        this.imagesService.addCanvasResource(query)
            .subscribe(response => {
                this.eventsEmitter.broadcast('Success', 'Changes Saved Succesfully');
            },
            error => {
                this.eventsEmitter.broadcast('Error', 'Error Occured');
            });
    }
}

<a data-html2canvas-ignore (click)="pdfDownload()">screenshot</a>

我正在调用的服务进行POST操作

 addCanvasResource(body: Object): Observable<any> {
        let bodyString = JSON.stringify(body);
        let headers = new Headers({ 'Content-Type': 'application/json' });
        let options = new RequestOptions({ headers: headers });

        return this.http.post(this.baseUrl + 'api/v3/images/AddCanvasImage', body, options)
            .map((response: Response) => {
                if (response.status < 200 || response.status >= 300) {
                    throw new Error('This request has failed ' + response.status);
                }
                else {
                    return response;
                }
            });
    }  

我无法访问html2canvas中的AddImagesResource()函数。 请告诉我如何实现上述功能。

- Pein

Answer 1

在 Angular 的 Promise 回调中，应该使用箭头函数（arrow functions）而不是匿名函数。箭头函数会正确地绑定当前上下文，因此您要调用的函数将会被访问到。

请尝试以下代码：

pdfDownload() {
    html2canvas(document.body).then(canvas => {
        var imgData = canvas.toDataURL("image/png");
        this.AddImagesResource(imgData);
        document.body.appendChild(canvas);
    });
}

- Daniel Galarza

Answer 2

请确保在angular-cli.json的脚本列表中导入脚本。

"scripts": [
"../node_modules/html2canvas/dist/html2canvas.min.js"
]

并且在类中如下：

import * as html2canvas from "html2canvas"

- Zohab Ali

---

这个是针对后续版本的Angular，应该在angular.json文件中吗？ - Wassim Katbey

Answer 3

pdfDownload() {
    let self = this;//use this variable to access your class members inside then().
    html2canvas(document.body).then(canvas => {
        var imgData = canvas.toDataURL("image/png");
        self.AddImagesResource(imgData);
        document.body.appendChild(canvas);
   });
}

- Mam's