Video Moving Water Mark

main.dart

import 'dart:async';
import 'dart:developer';
import 'dart:math' hide log;

import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: 'Material App',
      home: Page(),
    );
  }
}

class Info {
  final Size size;
  final Offset position;
  const Info({
    required this.size,
    required this.position,
  });
}

class Page extends StatefulWidget {
  const Page({Key? key}) : super(key: key);

  @override
  State<Page> createState() => _PageState();
}

class _PageState extends State<Page> {
  GlobalKey stickyKey = GlobalKey();
  OverlayEntry? entry;
  Timer? timer;

  @override
  void initState() {
    WidgetsBinding.instance.addPostFrameCallback((_) {
      init();
    });
    super.initState();
  }

  Info? getInfo() {
    final keyContext = stickyKey.currentContext;
    if (keyContext == null) return null;

    final box = keyContext.findRenderObject() as RenderBox;
    final pos = box.localToGlobal(Offset.zero);
    return Info(
      size: box.size,
      position: pos,
    );
  }

  void init() {
    final info = getInfo();
    if (info == null) {
      log("info is null");
      return;
    }

    timer = Timer.periodic(const Duration(milliseconds: 200), (_) {
      setOverlay(info.size, info.position);
    });
  }

  void setOverlay(Size size, Offset offset) {
    final overlay = Overlay.of(context);
    const s = Size(90, 40);

    double y = offset.dy;
    double x = offset.dx;

    final rand = Random();

    final h = rand.nextInt(size.height.toInt()) % size.height.toInt();
    final w = rand.nextInt(size.width.toInt()) % size.width.toInt();

    y += (h - s.height / 2);
    x += (w - s.width / 2);

    entry?.remove();

    log("$x, $y");

    entry = OverlayEntry(
      builder: (context) {
        return Positioned(
          top: y,
          left: x,
          child: Container(
            height: s.height,
            width: s.width,
            color: Colors.redAccent,
            child: const Material(
              child: Text(
                "Ahmed Mahmoud",
                style: TextStyle(
                  fontSize: 10,
                ),
              ),
            ),
          ),
        );
      },
    );
    overlay?.insert(entry!);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Material App Bar'),
      ),
      body: Center(
        child: Container(
          key: stickyKey,
          height: 300,
          width: 300,
          color: Colors.red.shade200,
          child: const Center(
            child: Text('Hello World'),
          ),
        ),
      ),
      floatingActionButton: Row(
        mainAxisSize: MainAxisSize.min,
        children: [
          FloatingActionButton(
            heroTag: "-",
            onPressed: getInfo,
          ),
          const SizedBox(width: 10),
          FloatingActionButton(
            heroTag: "--",
            backgroundColor: Colors.black,
            onPressed: () {
              timer?.cancel();
            },
          ),
        ],
      ),
    );
  }
}