创建ngSwitch新视图后,Angular2调用自定义函数

Question

我正在创建一个小应用程序Angular2+Ionic2.在这个程序我想初始化google-map到view segment当用户切换到map-segment使用ion-segment

以下是示例代码结构:

<ion-navbar *navbar class="hide-navbar">
    <ion-segment [(ngModel)]="homeSegment">
        <ion-segment-button value="list">
            List..
        </ion-segment-button>
        <ion-segment-button value="map" >
            Map
        </ion-segment-button>
    </ion-segment>
</ion-navbar>
<ion-content>
    <div [ngSwitch]="homeSegment" >

        <div *ngSwitchWhen="'map'">
            <div id="googleMap"></div>
        </div>

        <ion-list *ngSwitchWhen="'list'">
           Listing
        </ion-list>
    </div>
</ion-content>

我试过通过提供click听众ion-segment-button,但这没有成功.在附加之前div,添加地图的功能会被触发,结果会产生.id="googleMap"DOMundefined error

那么,我们如何理解何时发生新元素的加载ngSwitch？什么是最好的方法呢？

更新(添加js代码)

import {Page, NavController} from 'ionic-angular';
import {DataServiceManager} from '../../services/dataServicesManager';

@Page({
  templateUrl: 'build/pages/listFob/listFob.html'
})
export class ListFob {
    static get parameters(){
        return [[NavController],[DataServiceManager]];
    }
    onPageWillEnter(){
        this.fetchFobs();
    }
    ngOnInit(){
        console.log("on init");
        console.log(this.homeSegment);
    }
    ngAfterContentChecked() {
        console.log("content checked")
    }
    constructor(nav, dataServiceManager){
        this.nav = nav;
        this.dataServiceManager = dataServiceManager;
        this.homeSegment = "list";
    }
    loadMap(){
        console.log(document.getElementById("googleMapAllFobs"));
        // TODO: load map functionality
    }
}

添加指令时出现错误消息

./app/directives/switch-segment.js
Module build failed: SyntaxError: /Users/Piccaza/ionic-projects/learning/fob/app/directives/switch-segment.js: Unexpected token (8:27)
   6 | })
   7 | export class SwitchSegment {
>  8 |     @Output() switchSegment: EventEmitter = new EventEmitter();
     |                            ^
   9 |     ngOnInit() {
  10 |         console.log("Directive triggered!");
  11 |         this.onCreate.emit('dummy');
    at Parser.pp.raise (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:1378:13)
    at Parser.pp.unexpected (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:2817:8)
    at Parser.pp.expect (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:2811:33)
    at Parser.pp.parseMethod (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:1091:8)
    at Parser.pp.parseClassMethod (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:2495:8)
    at Parser.pp.parseClassBody (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:2456:10)
    at Parser.pp.parseClass (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:2339:8)
    at Parser.pp.parseStatement (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:1813:19)
    at Parser.pp.parseExportDeclaration (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:2578:15)
    at Parser.pp.parseExport (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:2566:29)
 @ ./app/pages/listFob/listFob.js 16:21-63 (CLI v2.0.0-beta.19)

Your system information:

Cordova CLI: Not installed
Ionic Version: 2.0.0-beta.3
Ionic CLI Version: 2.0.0-beta.19
Ionic App Lib Version: 2.0.0-beta.9
ios-deploy version: 1.8.5 
ios-sim version: 5.0.6 
OS: Mac OS X El Capitan
Node Version: v5.3.0
Xcode version: Xcode 7.2.1 Build version 7C1002 

Answer 1

ngSwitch添加/删除元素时没有对调用函数的内置支持。

我将创建一个指令，该指令在创建时调用该函数（例如在 中ngOnInit()）或发出一个可以绑定事件处理程序的事件，并将其应用于ngSwitch启用分支时添加的组件。

如果ngSwitch添加了一个组件，你也可以在这个组件中实现它（取决于你的要求）

更新

    <ion-list (onCreate)="doSomething()" *ngSwitchCase="'list'">
       Listing
    </ion-list>

@Directive(selector: '[onCreate]')
export class OnCreate implements OnInit {
  @Output() onCreate:EventEmitter = new EventEmitter();

  ngOnInit() {
    this.onCreate.emit('dummy');
  }
}

Plunker 示例