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main.ts

index.html

import { bootstrapApplication } from '@angular/platform-browser';
import { Component, ViewChild, ElementRef, AfterViewInit } from '@angular/core';
import { CommonModule } from '@angular/common';

@Component({
  selector: 'app-root',
  standalone: true,
  imports: [CommonModule],
  styles: [`
    .panel { padding: 12px; border: 1px solid #ccc; border-radius: 6px; }
    .row { display: grid; grid-template-columns: 1fr auto; gap: 8px; align-items: center; }
    input { padding: 6px 8px; }
  `],
  template: `
    <h3>ViewChild & AfterViewInit</h3>
    <div #panel class="panel">
      <div class="row">
        <input #box type="text" placeholder="Focused after view init" />
        <button (click)="measure()">Measure</button>
      </div>
      <p>Panel size: {{ size }}</p>
    </div>
  `
})
export class App implements AfterViewInit {
  @ViewChild('box') box; // ElementRef<HTMLInputElement>
  @ViewChild('panel') panel; // ElementRef<HTMLDivElement>
  size = '';

  ngAfterViewInit() {
    // Focus input once view is initialized, then measure panel
    setTimeout(() => {
      this.box?.nativeElement?.focus?.();
      this.measure();
    });
  }

  measure() {
    const el = this.panel?.nativeElement;
    if (!el) return;
    const rect = el.getBoundingClientRect();
    this.size = `${Math.round(rect.width)}×${Math.round(rect.height)}`;
  }
}

bootstrapApplication(App);

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Angular Lifecycle - ViewChild & AfterViewInit</title>
</head>
<body>
  <app-root></app-root>
</body>
</html>