Angular 2更改属性 [英] Angular 2 change attributes

问题描述

我有一个组件，该组件具有一组3个自定义按钮，我想将这些按钮用作录音机的控件.我陷入了第一阶段，在那里我想根据按钮的功能更改按钮上显示的符号.我试图通过更改它们的xlink:href属性(我使用svg)来实现这一点，但是在控制台EXCEPTION: Error in ./RecordComponent class RecordComponent - inline template:5:45 caused by: this.roundButtonOne.getAttribute is not a function中得到了它.知道为什么以及如何使用Angular2方法实现这一点吗?这是代码:

I have a component which features a set of 3 custom buttons and I want to use these buttons as controls for a sound recorder. I got stuck in the first phase, where I want to change the symbols displayed on the buttons, according to their function. I tried to achieve that by changing their xlink:href attributes(I use svg), but got this in he console EXCEPTION: Error in ./RecordComponent class RecordComponent - inline template:5:45 caused by: this.roundButtonOne.getAttribute is not a function. Any idea why and how I could implement this with an Angular2 approach? Here is the code:

import {Component, ViewChild} from '@angular/core';

@Component({
  selector: 'app-record',
  template: `
    <svg class='roundButtonOne icon'>
      <use #roundButtonOne xlink:href='#mic'(click)='onRecord()'/>
    </svg>
    <svg class='roundButtonTwo icon'>
      <use #roundButtonTwo xlink:href='#live' />
    </svg>
    <svg class='roundButtonThree icon'>
      <use #roundButtonThree xlink:href='#upload' />
    </svg>
   </div>
    `
})

export class RecordComponent {

  private recording: boolean = false;

  @ViewChild('roundButtonOne') roundButtonOne: HTMLElement;
  @ViewChild('roundButtonTwo') roundButtonTwo: HTMLElement;
  @ViewChild('roundButtonThree') roundButtonThree: HTMLElement;


  onRecord(){
    this.recording = true;
    switch(this.roundButtonOne.getAttribute('xlink:href')){
      case '#mic':
        this.record();
        break;
    }
  }
  record(){
    this.roundButtonOne.setAttribute('xlink:href','#mic-small');
    this.roundButtonTwo.setAttribute('xlink:href', '#pause');
    this.roundButtonThree.setAttribute('xlink:href', '#stop');
  }
}

推荐答案

如果在按钮元素之一上调用 console.log ，您会看到它是 ElementRef的实例. ，而不是 HTMLElement .

If you call console.log on one of the button elements, you can see that it is an instance of ElementRef, not HTMLElement.

所以...

从@ angular/core导入ElementRef:

Import ElementRef from @angular/core:

import {Component, ViewChild, ElementRef} from '@angular/core';

将按钮类型从HTMLElement更改为ElementRef:

Change the buttons type from HTMLElement to ElementRef:

@ViewChild('roundButtonOne') roundButtonOne: ElementRef;
@ViewChild('roundButtonTwo') roundButtonTwo: ElementRef;
@ViewChild('roundButtonThree') roundButtonThree: ElementRef;

从 ElementRef 对象获取 nativeElement ，然后调用 setAttribute()/ getAttribute()方法:

Get nativeElement from ElementRef object and then call setAttribute() / getAttribute() methods:

this.roundButtonOne.nativeElement.getAttribute('xlink:href');

this.roundButtonOne.nativeElement.setAttribute('xlink:href','#mic-small');

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