Angular Material: How to set each mat-horizontal-stepper stepper icon with different background color in TS

Question

I'm unable to set the icon colors

I have a mat-horizontal-stepper with five mat-steps (e.g. named Part A, Part B ... Part E). Each part (mat-step) may have different colors depending some business rules.

I know how to change the "selected" mat-step or how to change the color for ALL the mat-steps (with the same color) but can't figure out how to change it dynamically so each Part may have different icon background colors.

Using Angular v7

The following is a style to set the third mat-step icon green. Id does work but I don't how to change the color dynamically at run-time from the component (typescript).

::ng-deep .mat-step-header:nth-of-type(3) .mat-step-icon         {
    background-color: green!important; 
 }

Also I tried using [ngClass] but it is ignored when used as a mat-step attribute. It only works if I enclose the step label within and use it there but that is not the requirement (I need to change the background color of the icon... not the labels).

Expected result: Able to set each each step with different columns depending the level of completion for each step. (mat-steps could be a combination of yellow, red, green and black),

Actual result: Unable to change icon colors based on component variable settings

Akber Iqbal Akber Iqbal · Accepted Answer · 2019-07-30T05:47:27

The question is really about controlling CSS variables via TS - i got help from this post here;

CSS: we assign the 3 variables to the 3 icons which we needed to color
HTML: We created 2 divs firstClass & secondClass in addition to the <body>, to which we can assign the uniquely named variables color1, color2 and color3;
Since we are using 'mat-table' we can't use [ngStyle] or [ngClass] because the material elements are created at run time and we can only operate on any of them AfterViewInit event, so it is here that we assign values to our 2 divs & <body> tag;

relevant CSS:

::ng-deep .mat-step-header:nth-of-type(1) .mat-step-icon {
    background-color: var(--my-var1);
 } 

::ng-deep .mat-step-header:nth-of-type(2) .mat-step-icon {
    background-color: var(--my-var2);
 } 

::ng-deep .mat-step-header:nth-of-type(3) .mat-step-icon {
    background-color: var(--my-var3);
 }

relevant HTML:

<div class='firstClass'>
    <div class=' secondClass'>
        <mat-horizontal-stepper labelPosition="bottom" #stepper>
            <mat-step [stepControl]="firstFormGroup">
                <form [formGroup]="firstFormGroup">
                    <ng-template matStepLabel>Fill out your name</ng-template>
                    <mat-form-field>
                        <input matInput placeholder="Last name, First name" formControlName="firstCtrl" required>
            </mat-form-field>
            <div>
                <button mat-button matStepperNext>Next</button>
            </div>
        </form>
    </mat-step>
    <mat-step [stepControl]="secondFormGroup" optional>
        <form [formGroup]="secondFormGroup">
            <ng-template matStepLabel>Fill out your address</ng-template>
            <mat-form-field>
                <input matInput placeholder="Address" formControlName="secondCtrl" required>
            </mat-form-field>
            <div>
                <button mat-button matStepperPrevious>Back</button>
                <button mat-button matStepperNext>Next</button>
            </div>
        </form>
    </mat-step>
    <mat-step>
        <ng-template matStepLabel>Done</ng-template>
        You are now done.
        <div>
            <button mat-button matStepperPrevious>Back</button>
            <button mat-button (click)="stepper.reset()">Reset</button>
        </div>
    </mat-step>
  </mat-horizontal-stepper>
  <div>
<div>

relevant TS:

import {Component, OnInit,AfterViewInit } from '@angular/core';
import {FormBuilder, FormGroup, Validators} from '@angular/forms';

@Component({
  selector: 'stepper-label-position-bottom-example',
  templateUrl: 'stepper-label-position-bottom-example.html',
  styleUrls: ['stepper-label-position-bottom-example.css'],
})
export class StepperLabelPositionBottomExample implements OnInit, AfterViewInit {
  firstFormGroup: FormGroup;
  secondFormGroup: FormGroup;
  color1:string = 'green';
  color2:string = 'yellow';
  color3:string = 'red';

  constructor(private _formBuilder: FormBuilder) {}

  ngOnInit() {
    this.firstFormGroup = this._formBuilder.group({
      firstCtrl: ['', Validators.required]
    });
    this.secondFormGroup = this._formBuilder.group({
      secondCtrl: ['', Validators.required]
    });
  }

  ngAfterViewInit(){
    document.querySelector("body").style.cssText = "--my-var1: "+this.color1;
    (<HTMLElement>document.querySelector('.secondClass')).style.cssText = "--my-var2: "+this.color2;
    (<HTMLElement>document.querySelector('.firstClass')).style.cssText = "--my-var3: "+this.color3;
  }

}

complete working stacblitz here

Angular Material: How to set each mat-horizontal-stepper stepper icon with different background color in TS

1 Answers