import 'package:flutter/material.dart';
import 'package:get/get.dart';
import 'package:getx/controller.dart';

void main() {
  runApp(GetMaterialApp(
    home: Home(),
  ));
}

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

  @override
  Widget build(BuildContext context) {
    final controller = Get.put(Controller());
    return Scaffold(
      appBar: AppBar(
        title: Text('GetX Demo'),
        centerTitle: true,
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          GestureDetector(
            onTap: () {
              Get.to(Other());
            },
            child: Container(
              height: 200,
              width: 200,
              color: Colors.red,
              child: Align(
                alignment: Alignment.bottomCenter,
                child: Obx(() => Text(
                      controller.count.toString(),
                      style: TextStyle(fontSize: 50, color: Colors.white),
                    )),
              ),
            ),
          )
        ],
      ),
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.add),
        onPressed: () {
          controller.increment();
        },
      ),
    );
  }
}

class Other extends StatelessWidget {
  // 你可以让Get找到一个正在被其他页面使用的Controller，并将它返回给你。
  final Controller c = Get.find();

  @override
  Widget build(context) {
    // 访问更新后的计数变量
    return Scaffold(
        appBar: AppBar(
          leading: GestureDetector(
            onTap: () {
              Get.back();
            },
            child: Icon(Icons.arrow_back),
          ),
        ),
        body: Center(child: Text("${c.count}")));
  }
}

完整视频教程查看
https://www.bilibili.com/video/BV1e5411N757?p=2