将类添加到Angular 4中的元素

Question

我试图用Angular 4创建一个图库.这背后的逻辑是为所选图像添加一个层叠样式表(CSS)类,它将在所选(单击)图像上显示红色边框.这是图库的CSS样式表.

我想在我点击的图像上显示一个红色选区.this-is-a-class应添加到所选图像.

#container{
  border:1px solid red;
  height:auto;
}

ul li{
  margin-right:20px;
  margin-left:0;
  list-style-type:none;
  display:inline;
}

ul li img{
  width: 200px;
  height:200px;
  border:1px solid grey;
}

#select{
  border:2px solid violet;
}

.this-is-a-class{
  border: 10px solid red !important;
}

以下是模板代码

<div id="container">
  <ul>
    <li><img class="this-is-a-class" id="1" src="../../assets/images/1.jpg" (click)="addClass(id=1)"/></li>
    <li><img id="select" src="../../assets/images/2.png" (click)="addClass(id=2)"/></li>
    <li><img id="3" src="../../assets/images/3.jpg" (click)="addClass(id=3)"/></li>
    <li><img id="4" src="../../assets/images/4.png" (click)="addClass(id=4)"/></li>
    <li><img id="5" src="../../assets/images/5.jpg" (click)="addClass(id=5)"/></li>
  </ul>
</div>

<div>
  <h1>You Clicked on: {{id}}</h1>
</div>

组件代码如下

import { Component, OnInit } from '@angular/core';
import { DataService } from '../../services/data.service';

@Component({
  selector: 'app-user',
  templateUrl: './user.component.html',
  styleUrls: ['./user.component.css']
})

export class UserComponent implements OnInit {
  id: number;
  constructor() {
    console.log("Constructor working..")

  }

  ngOnInit() {
    console.log('ngOnInit works..');
  }

  //function to add the class to selected image to show the border.
  addClass(id) {
    this.id = id;
    //id = this.id? 'selectedImg' : 'null';
  }
}

Answer 1

根据使用[ngClass]和有条件地应用类id.

在您的HTML文件中:

<li>
    <img [ngClass]="{'this-is-a-class': id === 1 }" id="1"  
         src="../../assets/images/1.jpg" (click)="addClass(id=1)"/>
</li>
<li>
    <img [ngClass]="{'this-is-a-class': id === 2 }" id="2"  
         src="../../assets/images/2.png" (click)="addClass(id=2)"/>
</li>

在您的TypeScript文件中:

addClass(id: any) {
    this.id = id;
}

Answer 2

如果您只想设置一个特定的类，您可以编写一个返回布尔值的 TypeScript 函数来确定何时应附加该类。

打字稿

function hideThumbnail():boolean{
    if (/* Your criteria here */)
        return true;
}

CSS :

.request-card-hidden {
    display: none;
}

HTML :

<ion-note [class.request-card-hidden]="hideThumbnail()"></ion-note>

Answer 3

这是一个显示如何在指令中使用它的插件ngClass。

我是用divs而不是imgs 演示。

模板：

<ul>
      <li><div [ngClass]="{'this-is-a-class': selectedIndex == 1}" (click)="setSelected(1)"> </div></li>
      <li><div [ngClass]="{'this-is-a-class': selectedIndex == 2}" (click)="setSelected(2)"> </div></li>
      <li><div [ngClass]="{'this-is-a-class': selectedIndex == 3}" (click)="setSelected(3)"> </div></li>
</ul>

TS：

export class App {
  selectedIndex = -1;

  setSelected(id: number) {
    this.selectedIndex = id;
  }
}