在 Angular 4 上使用 Chart.js

Using Chart.js on Angular 4(在 Angular 4 上使用 Chart.js)

问题描述

我正在尝试将 Chart.js 与 Angular 4 一起使用，我在 chart.js 文档中看到了一个示例，但它使用的是 <script > 标签来拉取脚本，使其在组件上不起作用.这就是我尝试融入 Angular 的方式:

I'm trying to use Chart.js with Angular 4, I saw an example on the chart.js documents but it's using a < script > tag to pull the script so it doesn't work on the component. This is how I tried to fit into Angular:

TS

export class GraphicsComponent implements OnInit {

  ctx = document.getElementById("myChart");
  myChart = new Chart(this.ctx, {
    type: 'pie',
    data: {
        labels: ["New", "In Progress", "On Hold"],
        datasets: [{
            label: '# of Votes',
            data: [1,2,3],
            backgroundColor: [
                'rgba(255, 99, 132, 1)',
                'rgba(54, 162, 235, 1)',
                'rgba(255, 206, 86, 1)'
            ],
            borderWidth: 1
        }]
    },
    options: {
      responsive: false,
      display:true
    }
  });

  constructor() { }

  ngOnInit() {
  }

}

HTML

<canvas id="myChart" width="700" height="400"></canvas>

知道如何让它发挥作用吗?

Any idea how I would make it work?

我已使用导入更新了我的代码，但现在收到错误消息.

I have updated my code with the import and I'm now receiving an error.

导入代码:

import * as Chart from 'chart.js'

Chrome 控制台出错:

ERROR Error: Uncaught (in promise): TypeError: Cannot read property 'length' of null
TypeError: Cannot read property 'length' of null
    at Object.acquireContext (platform.dom.js:333)
    at Chart.construct (core.controller.js:74)
    at new Chart (core.js:42)
    at new GraphicsComponent (graphics.component.ts:12)
    at createClass (core.es5.js:10922)
    at createDirectiveInstance (core.es5.js:10756)
    at createViewNodes (core.es5.js:12197)
    at createRootView (core.es5.js:12092)
    at callWithDebugContext (core.es5.js:13475)
    at Object.debugCreateRootView [as createRootView] (core.es5.js:12792)
    at Object.acquireContext (platform.dom.js:333)
    at Chart.construct (core.controller.js:74)
    at new Chart (core.js:42)
    at new GraphicsComponent (graphics.component.ts:12)
    at createClass (core.es5.js:10922)
    at createDirectiveInstance (core.es5.js:10756)
    at createViewNodes (core.es5.js:12197)
    at createRootView (core.es5.js:12092)
    at callWithDebugContext (core.es5.js:13475)
    at Object.debugCreateRootView [as createRootView] (core.es5.js:12792)
    at resolvePromise (zone.js:795)
    at resolvePromise (zone.js:766)
    at zone.js:844
    at ZoneDelegate.webpackJsonp.../../../../zone.js/dist/zone.js.ZoneDelegate.invokeTask (zone.js:425)
    at Object.onInvokeTask (core.es5.js:3881)
    at ZoneDelegate.webpackJsonp.../../../../zone.js/dist/zone.js.ZoneDelegate.invokeTask (zone.js:424)
    at Zone.webpackJsonp.../../../../zone.js/dist/zone.js.Zone.runTask (zone.js:192)
    at drainMicroTaskQueue (zone.js:602)
    at <anonymous>

推荐答案

您可以安装包，以及在 Angular 等打字稿环境中获得完整功能的类型:

You can install the package, along with the types for full functionality in a typescript environment such as Angular:

npm install --save chart.js &&npm install --save-dev @types/chart.js

然后在您的组件中，您现在可以 import * as Chart from 'chart.js' 并在您的 typescript 环境中使用它.查看这个例子使用打字稿的实现方法.

Then in your component you can now import * as Chart from 'chart.js' and use it in your typescript environment. Check out this example for implementation methods using typescript.

因为您需要从 DOM 中获取画布，所以在尝试访问它之前需要确保它已被渲染.这可以通过 AfterViewInit 来完成.

Because you need to get the canvas from the DOM you need to make sure it's rendered before attempting to access it. This can be accomplished with AfterViewInit.

import { Component, AfterViewInit } from '@angular/core';
import * as Chart from 'chart.js'

export class MyChartComponent implements AfterViewInit {

  canvas: any;
  ctx: any;

  ngAfterViewInit() {
    this.canvas = document.getElementById('myChart');
    this.ctx = this.canvas.getContext('2d');
    let myChart = new Chart(this.ctx, {
      type: 'pie',
      data: {
          labels: ["New", "In Progress", "On Hold"],
          datasets: [{
              label: '# of Votes',
              data: [1,2,3],
              backgroundColor: [
                  'rgba(255, 99, 132, 1)',
                  'rgba(54, 162, 235, 1)',
                  'rgba(255, 206, 86, 1)'
              ],
              borderWidth: 1
          }]
      },
      options: {}
    });
  }

}

这篇关于在 Angular 4 上使用 Chart.js的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！