Chart.js 如果主页上不存在，则不会在 Angular2 中显示

Question

每当我将图表转储到主 app.component.html 时似乎都很好，但是一旦我在子组件中使用它并将应用程序路由到它，图表就不会显示。在检查器窗口中，它显示元素具有 0 高度和 0 宽度。有没有人可以解决这个问题？

这是我的 app.component.ts 的代码：

import {Component} from 'angular2/core';
import {RouteConfig, ROUTER_DIRECTIVES} from 'angular2/router';

import {HomeComponent} from './home.component';
import {ProfileComponent} from './profile.component';
import {HoursComponent} from './hours.component';
import {SettingsComponent} from './settings.component';
import {TaskComponent} from './task.component';
import {ChartDirective} from './chart.directive';


@Component({
    selector: 'track-me',
    templateUrl: 'app/app.component.html',
    directives: [ROUTER_DIRECTIVES,ChartDirective]    
})

@RouteConfig([
    { path: '/', component: HomeComponent, name: 'Home' },
    { path: '/home', component: HomeComponent, name: 'Home' },
    { path: '/profile', component: ProfileComponent, name: 'Profile' },
    { path: '/hours', component: HoursComponent, name: 'Hours' },
    { path: '/settings', component: SettingsComponent, name: 'Settings' },
    { path: '/task', component: TaskComponent, name: 'Task' },
])

export class AppComponent { }

这是我的 app.component.html 的代码：

<ul class="nav navmenu-nav">
    <li><a [routerLink]="['/Home']">Home</a></li> 
    <li><a [routerLink]="['/Profile']">Profile</a></li> 
    <li><a [routerLink]="['/Hours']">Set Hours</a></li> 
    <li><a [routerLink]="['/Settings']">Settings</a></li>
    <li><a [routerLink]="['/Task']">Completed Task</a></li>
</ul>

<router-outlet></router-outlet>
<canvas id="myChart" chart height="250" width="350"></canvas>

html 页面上的 canvas 元素会显示得很好。但是，一旦我把它放在我的 home.component 中，它就不会显示了。

这是我的 home.component.ts：

import {Component} from 'angular2/core';
import {ChartDirective} from './chart.directive';
import {TopicsComponent} from './topics.component';

@Component({
    selector: 'home',
    templateUrl: 'app/home.component.html',
    directives: [TopicsComponent, ChartDirective]
})

export class HomeComponent { }

这是我的 home.component.html：

<div class="container details-container">
  <topics></topics>
</div>

<div class="graph-container">
    <div class="row no-pad" style="position: relative;">
        <div style="margin-left:14px; z-index: 100; height: 250px;">    
            <canvas id="myChart" chart height="250" width="350"></canvas>
        </div>  
        <div class="vaxis-bar"></div>
    </div><!--/row-->
    <div class="row">
        <div class="col-sm-12 text-center bottom-row">
            HOURS(9)
        </div>
    </div>
</div>

最后，这是我的 chart.directive.ts：

/// <reference path="../node_modules/chart.js/chart.d.ts" />

import {Directive, ElementRef, Renderer, Input} from 'angular2/core';
@Directive({
    selector: '[chart]'
})
export class ChartDirective {
    constructor(el: ElementRef, renderer: Renderer) {
        //el.nativeElement.style.backgroundColor = 'yellow';
        var data = {
            labels: ["", "", "", "", "", "", "", "", ""],
            datasets: [
                {
                    label: "Track Me",
                    fillColor: "rgba(220,220,220,0.2)",
                    strokeColor: "rgba(13,220,138,1)",
                    pointColor: "rgba(13,220,138,1)",
                    pointStrokeColor: "#fff",
                    pointHighlightFill: "#fff",
                    pointHighlightStroke: "rgba(220,220,220,1)",
                    data: [1, 3, 13, 7, 0, 5, 9, 2, 5]
                }
            ]
        };
        var opts = {
            pointDot: false, scaleFontColor: "#50728d", scaleShowLabels: true, responsive: false, scaleLineColor: "rgba(255,255,255,.3)"
        };

        var ctx: any = el.nativeElement.getContext("2d");
        var lineChart = new Chart(ctx);
        ////var lineChartOptions = areaChartOptions;
        ////lineChartOptions.datasetFill = false;
        lineChart.Line(data,opts);             

    }

}

Answer 1

好的，这就是我解决问题的方法。我只使用 canvas 元素创建了一个新的 canvas 组件，并将我的图表指令导入到新组件中。之后，每当我创建我的主组件的实例时，我都会使用 DynamicComponentLoader 类来动态加载我的组件。

新的 home.component.ts：

import {Component, DynamicComponentLoader, Injector} from 'angular2/core';
import {TopicsComponent} from './topics.component';
import {CanvasComponent} from './canvas.component';

@Component({
    selector: 'home',
    templateUrl: 'app/home.component.html',
    directives: [TopicsComponent, CanvasComponent]
})

export class HomeComponent { 
    constructor(dcl: DynamicComponentLoader, injector: Injector) {
        dcl.loadAsRoot(CanvasComponent, '#chartInsert', injector);
    }
}

新建 home.component.html

<div class="container details-container">
  <topics></topics>
</div>

<div class="graph-container">
    <div class="row no-pad" style="position: relative;">
        <div style="margin-left:14px; z-index: 100; height: 250px;" id="chartInsert">   
        </div>  
        <div class="vaxis-bar"></div>
    </div><!--/row-->
    <div class="row">
        <div class="col-sm-12 text-center bottom-row">
            HOURS(9)
        </div>
    </div>
</div>

新建 canvas.component.ts

import {Component} from 'angular2/core';
import {ChartDirective} from './chart.directive';

@Component({
    selector: 'canvas-component',
    template: '<canvas id="myChart" chart height="250" width="350"></canvas>',
    directives: [ChartDirective]
})

export class CanvasComponent { }

我希望这可以帮助别人。

Answer 2

关于 ElementRef https://github.com/angular/angular/blob/master/CHANGELOG.md#200-beta3-2016-02-03，Angular 2.0.0-beta.3 发生了重大变化。与其在构造函​​数中使用 ElementRef，不如将 ngOnInit 视为 LifeCycle 钩子https://angular.io/docs/ts/latest/guide/lifecycle-hooks.html