ngFor循环内的第二个图表不可见

Question

我正在创建一个跟踪家庭预算的应用程序。我需要向用户显示每个月的收入和支出以及支出的饼图。我正在模板中的ngFor中遍历对象数组。

我希望能够为每个所谓的“月”显示饼图，其中每个budget为budget[]，但只能看到第一个饼图。

这里是https://stackblitz.com/github/avaliaho/budgettracker的Stackblitz，下面是相关的代码段：

monthlybudget.component.html：

<div class="row">
  <main role="main" class="col-md-9 ml-sm-auto col-lg-10 px-4">
    <div *ngFor="let budget of budgets">
      <div class="card">
        <div class="card-body">
          <h5 class="card-title">{{ budget.date | date }}</h5>

          <canvas id="myChart" style="margin-bottom: 12px;" width="800" height="250px" #mychart></canvas>

          <table class="table table-responsive">
            <thead>
              <tr>
                <th>Food</th>
                <th>Drinks</th>
                <th>Housing</th>
                <th>Bills</th>
                <th>Loans</th>
                <th>Travel</th>
                <th>Clothing</th>
                <th>Insuraces</th>
                <th>Hobby</th>
                <th>Other</th>
                <th>Income</th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td>{{ budget.food }}€</td>
                <td>{{ budget.drinks }}€</td>
                <td>{{ budget.housing }}€</td>
                <td>{{ budget.bills }}€</td>
                <td>{{ budget.loans }}€</td>
                <td>{{ budget.travel }}€</td>
                <td>{{ budget.clothing }}€</td>
                <td>{{ budget.insurances }}€</td>
                <td>{{ budget.hobby }}€</td>
                <td>{{ budget.other }}€</td>
                <td>{{ budget.income }}€</td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
      <br>
    </div>

  </main>
</div>

monthlybudget.component.ts：

import { Component, OnInit, ViewChild } from '@angular/core';
import { BudgetService } from '../budget.service';
import { budget } from '../budget.interface';
import { Chart } from 'chart.js';

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

  budgets: budget[] = [];
  canvas: any;
  ctx: any;
  @ViewChild('mychart') mychart;

  constructor(private service: BudgetService) {}

  ngOnInit() {
    this.budgets = this.service.getAll();
  }

  ngAfterViewInit() {
    this.canvas = this.mychart.nativeElement; 
    this.ctx = this.canvas.getContext('2d');

    let myChart = new Chart(this.ctx, {
      type: 'pie',

      data: {
        datasets: [{
          label: 'Expenses',
          backgroundColor: "rgba(0, 123, 255,0.4)",
          borderColor: "rgb(0, 123, 255)",
          fill: true,
          data: [
            this.budgets[0].drinks, 
            this.budgets[0].food, 
            this.budgets[0].hobby, 
            this.budgets[0].housing,
            this.budgets[0].insurances,
            this.budgets[0].loans, 
            this.budgets[0].netflix, 
            this.budgets[0].other
          ],
        }],
        labels: ['Drinks', 'Food', 'Hobby', 'Housing', 'Insurance', 'Loans', 'Netflix', 'Other']
      },
      options: {
        responsive: true,
        title: {
          display: true,
          text: 'Expenses'
        }
      }
    });
  }

}