Dynamically updating css in Angular 2

问题:

Let's say I have an Angular2 Component

//home.component.ts

import { Component } from 'angular2/core';

@Component({
    selector: "home",
    templateUrl: "app/components/templates/home.component.html",
    styleUrls: ["app/components/styles/home.component.css"]
})
export class HomeComponent {
    public width: Number;
    public height: Number;
} 

The template html file for this component

//home.component.html

<div class="home-component">Some stuff in this div</div>

And finally the css file for this component

//home.component.css

.home-component{
    background-color: red;
    width: 50px;
    height: 50px;
}

As you can see there are 2 properties in the class, width and height. I would like the css styles for width and height to match the values of the width and height properties and when the properties update, the width and height of the div update. What is the proper way to accomplish this?

回答1:

Try this

 <div class="home-component" 
 [style.width.px]="width" 
 [style.height.px]="height">Some stuff in this div</div>

[Updated]: To set in % use

[style.height.%]="height">Some stuff in this div</div>

回答2:

To use % instead of px or em with @Gaurav's answer, it's just

<div class="home-component" [style.width.%]="80" [style.height.%]="95">
Some stuff in this div</div>

回答3:

This should do it:

<div class="home-component" 
     [style.width]="width + 'px'" 
     [style.height]="height + 'px'">Some stuff in this div</div>

回答4:

You can also use hostbinding:

import { HostBinding } from '@angular/core';

export class HomeComponent {
    @HostBinding('style.width') width: Number;
    @HostBinding('style.height') height: Number;
} 

Now when you change the width or height property from within the HomeComponent, this should affect the style attributes.

回答5:

The accepted answer is not incorrect.

For grouped styles one can also use the ngStyle directive.

<some-element [ngStyle]="{'font-style': styleExpression, 'font-weight': 12}">...</some-element>

The official docs are here

回答6:

Check working Demo here

import {Component,bind} from 'angular2/core';
import {bootstrap} from 'angular2/platform/browser';
import {FORM_DIRECTIVES} from 'angular2/form';

import {Directive, ElementRef, Renderer, Input,ViewChild,AfterViewInit} from 'angular2/core';

@Component({
  selector: 'my-app',
    template: `
    <style>
       .myStyle{
        width:200px;
        height:100px;
        border:1px solid;
        margin-top:20px;
        background:gray;
        text-align:center;
       }
    </style>

          <div [class.myStyle]="my" [style.background-color]="randomColor" [style.width]="width+'px'" [style.height]="height+'px'"> my width={{width}} & height={{height}}</div>
    `,
    directives: []
})

export class AppComponent {
  my:boolean=true;
  width:number=200px;
  height:number=100px;
  randomColor;
  randomNumber;
  intervalId;
  textArray = [
    'blue',
    'green',
    'yellow',
    'orange',
    'pink'
  ];


  constructor() 
  {
    this.start();
  }

      start()
      { 
        this.randomNumber = Math.floor(Math.random()*this.textArray.length);
        this.randomColor=this.textArray[this.randomNumber];
        console.log('start' + this.randomNumber);
        this.intervalId = setInterval(()=>{
         this.width=this.width+20;
         this.height=this.height+10;
         console.log(this.width +" "+ this.height)
         if(this.width==300)
         {
           this.stop();
         }

        }, 1000);
      }
      stop()
      {
        console.log('stop');
        clearInterval(this.intervalId);
        this.width=200;
        this.height=100;
        this.start();

      }
 }

bootstrap(AppComponent, []);

回答7:

You can dynamically change the style(width and height) of div by attaching dynamic value to inline [style.width] and [style.hiegh] property of div.

In your case you can bind width and height property of HomeComponent class with the div's inline style width and height property like this... As directed by Sasxa

<div class="home-component" 
     [style.width]="width + 'px'" 
     [style.height]="height + 'px'">Some stuff in this div
</div>

For the working demo take a look at this plunker(http://plnkr.co/edit/cUbbo2?p=preview)

   //our root app component
import {Component} from 'angular2/core';
import {FORM_DIRECTIVES,FormBuilder,AbstractControl,ControlGroup,} from "angular2/common";

@Component({
  selector: 'home',
  providers: [],
  template: `
     <div class="home-component" [style.width]="width+'px'" [style.height]="height+'px'">Some this div</div>
     <br/>
     <form [ngFormModel]="testForm">
        width:<input type="number" [ngFormControl]="txtWidth"/> <br>
        Height:<input type="number"[ngFormControl]="txtHeight" />
     </form>
  `,
  styles:[`

      .home-component{
        background-color: red;
        width: 50px;
        height: 50px;
    }

  `],
  directives: [FORM_DIRECTIVES]
})
export class App {
  testForm:ControlGroup;
  public width: Number;
  public height: Number;
  public txtWidth:AbstractControl;
  public txtHeight:AbstractControl;

  constructor(private _fb:FormBuilder) {
      this.testForm=_fb.group({
        'txtWidth':['50'],
        'txtHeight':['50']
      });

      this.txtWidth=this.testForm.controls['txtWidth'];
      this.txtHeight=this.testForm.controls['txtHeight'];

      this.txtWidth.valueChanges.subscribe(val=>this.width=val);
      this.txtHeight.valueChanges.subscribe(val=>this.height =val);
  }
}

回答8:

I liked the look of WenhaoWuI's idea above, but I needed to identify the div with class .ui-tree in the PrimeNG tree component to set the height dynamically. All the answers I could find required the div to be named (ie #treediv) to enable the use of @ViewChild(), @ViewChildren(), @ContentChild(), @ContentChilden() etc. This was messy with a third party component.

I finally found a snippet from Günter Zöchbauer :

ngAfterViewInit() {
  this.elRef.nativeElement.querySelector('.myClass');
}

This made it easy:

@Input() height: number;
treeheight: number = 400; //default value

constructor(private renderer: Renderer2, private elRef: ElementRef) {  }

ngOnInit() {
    this.loading = true;
    if (this.height != null) {
        this.treeheight = this.height;
    }   
}

ngAfterViewInit() {
    this.renderer.setStyle(this.elRef.nativeElement.querySelector('.ui-tree'), 'height', this.treeheight + "px");
}

回答9:

All the above answers are great. But if you were trying to find a solution that won't change the html files below is helpful

 ngAfterViewChecked(){
    this.renderer.setElementStyle(targetItem.nativeElement, 'height', textHeight+"px");
}

You can import renderer from import {Renderer} from '@angular/core';

回答10:

If you want to set width dynamically with variable than use [] braces instead {{}}:

 <div [style.width.px]="[widthVal]"  [style.height.px]="[heightVal]"></div>

 <div [style.width.%]="[widthVal]"  [style.height.%]="[heightVal]"></div>