扩展MostafaMashayekhi对选项二的答案> 你也可以用一个'，'连接多个选项

[ngClass]="{'my-class': step=='step1', 'my-class2':step=='step2' }"

此外，*ngIf也可以在某些情况下使用，通常与*ngFor结合使用

class="mats p" *ngIf="mat=='painted'"

该指令有三种不同的操作方式，这取决于表达式的计算结果是三种类型中的哪一种:

If the expression evaluates to a string, the string should be one or more space-delimited class names. If the expression evaluates to an object, then for each key-value pair of the object with a truthy value the corresponding key is used as a class name. If the expression evaluates to an array, each element of the array should either be a string as in type 1 or an object as in type 2. This means that you can mix strings and objects together in an array to give you more control over what CSS classes appear. See the code below for an example of this.

    [class.class_one] = "step === 'step1'"

    [ngClass]="{'class_one': step === 'step1'}"

对于多个选项:

    [ngClass]="{'class_one': step === 'step1', 'class_two' : step === 'step2' }" 

    [ngClass]="{1 : 'class_one', 2 : 'class_two', 3 : 'class_three'}[step]"

    [ngClass]="step == 'step1' ? 'class_one' : 'class_two'"

像这样试试。

用“

<ol class="breadcrumb">
    <li *ngClass="{'active': step==='step1'}" (click)="step='step1; '">Step1</li>
    <li *ngClass="{'active': step==='step2'}"  (click)="step='step2'">Step2</li>
    <li *ngClass="{'active': step==='step3'}" (click)="step='step3'">Step3</li>
</ol>

Angular version 2+提供了几种有条件地添加类的方法:

1型

    [class.my_class] = "step === 'step1'"

两个类型

    [ngClass]="{'my_class': step === 'step1'}"

并有多种选择:

    [ngClass]="{'my_class': step === 'step1', 'my_class2' : step === 'step2' }"

三个类型

    [ngClass]="{1 : 'my_class1', 2 : 'my_class2', 3 : 'my_class4'}[step]"

四个类型

    [ngClass]="step == 'step1' ? 'my_class1' : 'my_class2'"

您可以在文档页上找到这些示例

Angular提供了多种有条件地添加类的方法:

第一个方法

Active是您的类名

[class.active]="step === 'step1'"

第二种方式

Active是您的类名

[ngClass]="{'active': step=='step1'}"

第三条道路

通过使用三元运算符class1和class2是你的类名

[ngClass]="(step=='step1')?'class1':'class2'"

ngClass的正常结构是:

[ngClass]="{'classname' : condition}"

所以在你的情况下，就像这样使用它……

<ol class="breadcrumb">
  <li [ngClass]="{'active': step==='step1'}" (click)="step='step1'">Step1</li>
  <li [ngClass]="{'active': step==='step2'}" (click)="step='step2'">Step2</li>
  <li [ngClass]="{'active': step==='step3'}" (click)="step='step3'">Step3</li>
</ol>