Question

<ion-card *ngFor='#product of products | mapToIterable:"key":true'>
    <ion-list>
        <ion-item>
            <ion-label stacked>Account No. / Phone No.</ion-label>
            <ion-input type="text" [(ngModel)]="product.msisdn"></ion-input>
        </ion-item>
        <ion-item>
            <ion-label stacked>Amount</ion-label>
            <ion-input type="text" (keypress)="isNumberKey($event)" [(ngModel)]="product.amount"></ion-input>
        </ion-item>
    </ion-list>
</ion-card>

参考上面的html，如何获得离子输入的参考，以便在验证失败后我可以setFocus()。我已经提供了下面的代码来验证每个输入。

for (var product of <any>this.products) {
    if (product.service_type_id == 2 && !product.msisdn) {
        alert('something');
        //Get the element and set focus here.
    }
}

这是一个好方法吗？在Angular 2中有更好的处理方法吗？

Answer 1

获取使用*ngFor创建的元素的引用的方法是@ViewChildren()

如果元素实际上是组件或指令，则组件/指令类型可以作为参数传递，否则可以添加模板变量，模板变量的名称（作为字符串）可用于查询元素。

在这种情况下，模板变量和组件类型都返回组件实例，但是为了调用焦点，我们需要ElementRef.nativeElement因此我创建了一个应用于ion-input的辅助指令，用于查询元素以及调用focus()：

import {Component, Directive, Renderer, HostListener, ViewChildren, ElementRef} from 'angular2/core'

/// Helper directive
@Directive({
  selector: 'ion-input'
})
class Focusable {
  constructor(public renderer: Renderer, public elementRef: ElementRef) {}

  focus() {
    console.debug(this.elementRef.nativeElement);
    this.renderer.invokeElementMethod(
        this.elementRef.nativeElement, 'focus', []);
  }
}

/// Test component instead of the original ion-input
@Component({
    selector: 'ion-input',
    host: {'tabindex': '1'},
    template: `
    <div>input (focused: {{focused}})</div>
    `,
})
export class IonInput {
  focused:boolean = false;

  @HostListener('focus') 
  focus() {
    this.focused = true;
  }
  @HostListener('blur') 
  blur() {
    this.focused = false;
  }
}

/// Queries the elements and calls focus
@Component({
    selector: 'my-app',
    directives: [IonInput, Focusable],
    template: `
    <h1>Hello</h1>
<div *ngFor="let product of products">
  <ion-input #input type="text"></ion-input>
</div>   
<button *ngFor="let product of products; let index=index" (click)="setFocus(index)">set focus</button>
    `,
})
export class AppComponent {
  constructor(private renderer:Renderer) {
    console.debug(this.renderer)
  }

  products = ['a', 'b', 'c']
  @ViewChildren(Focusable) inputs;

  ngAfterViewInit() {
    // `inputs` is now initialized
    // iterate the elements to find the desired one
  }

  setFocus(index) {
    // `inputs` is now initialized
    // iterate the elements to find the desired one
    //var input = ...
    //console.debug(this.inputs.toArray()[1]);
    this.inputs.toArray()[index].focus();
  }  
}

另见Angular 2: Focus on newly added input element

Plunker example

Angular 2 - 访问/获取* ngFor和ngModel中的输入元素

1 个答案: