Component series.line not exists. Load it first.

Angular中使用echarts图标库时报了如下错误：

core.js:6189 ERROR Error: Component series.line not exists. Load it first.
    at Function.entity.getClass (clazz.js:178)
    at ExtendedClass. (Global.js:223)
    at Array.forEach ()
    at each (util.js:300)
    at ExtendedClass.visitComponent (Global.js:212)
    at Function.entity.topologicalTravel (component.js:125)
    at ExtendedClass.mergeOption (Global.js:194)
    at ExtendedClass.initBase (Global.js:663)
    at ExtendedClass.resetOption (Global.js:141)
    at ExtendedClass.setOption (Global.js:123)

检查了package.json，确认库已经安装好了:

"echarts": "^4.7.0",
"ngx-echarts": "^4.2.2",
"@types/echarts": "^4.4.6",

option的字段也是按照官方文档来设置的。检查模块导入时，发现是NgxEchartsModule没有导入，尝试导入:

import { NgxEchartsModule } from 'ngx-echarts';

@NgModule({
  declarations: [AppComponent],
  entryComponents: [],
  imports: [
    BrowserModule,
    IonicModule.forRoot(),
    AppRoutingModule,
    // ...
    NgxEchartsModule,
    // ...
    IonicStorageModule.forRoot(),
  ],
  providers: [
	// ...
  ],
  bootstrap: [AppComponent],
})
export class AppModule {}

重新编译程序恢复正常。