Angular2更新带有标签的ng2图表

Question

我现在开始使用Angular2工作,并对框架ng2-charts有疑问.

这是我的component.ts代码:

import { Component } from '@angular/core';
import { ChartsModule } from 'ng2-charts';
import { PredictionService } from './prediction.service'

@Component({
  selector: 'prediction-result-chart',
  templateUrl: './predictionResultChart.component.html'
})

export class PredictionResultChartComponent{

  public pieChartLabels:string[] = [];
  public pieChartData:number[] = [];
  public pieChartType:string = 'pie';
  public JSONobject = {}

  constructor(private predictionService: PredictionService){
    this.getPredictions();
  }

  public getPredictions() {
    this.predictionService.getPredictions('hello').do(result => this.populateChart(result)).subscribe();
  }

  public populateChart(obj): void{
    let labels:string[] = [];
    let data:number[] = [];
    for (var i = 0; i < obj.predictions.length; i++)
    {
      labels.push(String(obj.predictions[i].class));
      data.push(obj.predictions[i].percentage);
    };
    this.pieChartData = data;
    this.pieChartLabels = labels;
  }

  public chartClicked(e:any):void {}
  public chartHovered(e:any):void {}

}

该component.html代码:

<div style="display: block">
  <canvas baseChart
      [data]="pieChartData"
      [labels]="pieChartLabels"
      [chartType]="pieChartType"
      (chartHover)="chartHovered($event)"
      (chartClick)="chartClicked($event)"></canvas>
</div>

服务代码:

import { Injectable } from '@angular/core';
import { Http, Response, Headers } from '@angular/http';

import { Observable }     from 'rxjs/Observable';
import 'rxjs/add/operator/map';


@Injectable()
export class PredictionService {

  private baseUrl: string = 'http://localhost:8080/predict/';
  constructor(private http : Http){
  }

  getPredictions(text :string) {
    return this.http.get(this.baseUrl + text).map(res => res.json());
  }

}

使用上面的代码,这是我所拥有的,没有任何颜色的图表:

事实上,当我深入研究我的代码时,HTML组件在开始时获取变量然后更新它们.因此,当标签为空时,即使我添加了一些标签,它们也会被添加为未定义.所以我有一个图表,其中包含正确的值,但没有正确的标签.标记为未定义的所有内容.

如果我在开始时启动标签,我将会有一个带有正确值的彩色图表

所以我的问题是:

如何加载数据,然后呈现HTML组件？

反正有没有数据渲染chart.js组件并用正确的标签和数据更新它？

需要任何帮助,谢谢.

Answer 1

在标准chart.js中,您可以在.update()修改其数据(包括标签)后使用原型方法重新渲染图表.

但是,似乎ng2-charts没有提供触发更新的机制(根据这个github问题).我根本没有Angular2的经验,但也许这对你有用吗？该方法取自zbagley在17天前发布的github问题中发表的评论(遗憾的是,我无法找到一种方法来生成引用此特定评论的网址).

方法是在数据可用之前基本上不渲染图表.这是对component.ts代码的更改.

import { Component } from '@angular/core';
import { ChartsModule } from 'ng2-charts';
import { PredictionService } from './prediction.service'

@Component({
  selector: 'prediction-result-chart',
  templateUrl: './predictionResultChart.component.html'
})

export class PredictionResultChartComponent {    
  public pieChartLabels:string[] = [];
  public pieChartData:number[] = [];
  public pieChartType:string = 'pie';
  public JSONobject = {};
  public isDataAvailable:boolean = false;

  constructor(private predictionService: PredictionService){
    this.getPredictions();
  }

  public getPredictions() {
    this.predictionService.getPredictions('hello').do(result => this.populateChart(result)).subscribe();
  }

  public populateChart(obj): void {        
    let labels:string[] = [];
    let data:number[] = [];
    for (var i = 0; i < obj.predictions.length; i++)
    {
      labels.push(String(obj.predictions[i].class));
      data.push(obj.predictions[i].percentage);
    };
    this.pieChartData = data;
    this.pieChartLabels = labels;
    this.isDataAvailable = true;
  }

  public chartClicked(e:any):void {}
  public chartHovered(e:any):void {}    
}

然后您将ngIf在component.html代码中使用.

<div style="display: block" *ngIf="isDataAvailable">
  <canvas baseChart
      [data]="pieChartData"
      [labels]="pieChartLabels"
      [chartType]="pieChartType"
      (chartHover)="chartHovered($event)"
      (chartClick)="chartClicked($event)"></canvas>
</div>