具有类似_cameraOn = true的变量。如果为true，则显示CameraPreview，否则为false。导航到另一个屏幕时，将其设置为false

您可以在单独的小部件中拥有与相机相关的功能。因此，每次显示时都会对其进行初始化，而在不显示时将对其进行处理。

一个简单的工作示例

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:camera/camera.dart';

List<CameraDescription> cameras;

Future<void> main() async {
  cameras = await availableCameras();
  runApp(MaterialApp(
    home: CameraApp(),
  ));
}

class CameraApp extends StatefulWidget {
  @override
  _CameraAppState createState() => _CameraAppState();
}

class _CameraAppState extends State<CameraApp> {
  bool _cameraOn = true;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: <Widget>[
          Expanded(
            child: _cameraOn ? Camera() : Container(),
          ),
          FlatButton(
            onPressed: () {
              setState(() {
                _cameraOn = false;
              });
              Navigator.push(
                  context,
                  MaterialPageRoute(
                      builder: (BuildContext context) => Post())).then((res) {
                setState(() {
                  _cameraOn = true;
                });
              }).catchError((err) {
                print(err);
              });
            },
            child: Text("NEXT PAGE"),
          ),
        ],
      ),
    );
  }
}

class Camera extends StatefulWidget {
  @override
  _CameraState createState() => _CameraState();
}

class _CameraState extends State<Camera> {
  CameraController controller;

  @override
  void initState() {
    super.initState();
    controller = CameraController(cameras[0], ResolutionPreset.medium);
    controller.initialize().then((_) {
      if (!mounted) {
        return;
      }
      setState(() {});
    });
  }

  @override
  Widget build(BuildContext context) {
    if (!controller.value.isInitialized) {
      return Container();
    }

    return AspectRatio(
      aspectRatio: controller.value.aspectRatio,
      child: CameraPreview(controller),
    );
  }

  @override
  void dispose() {
    controller?.dispose();
    super.dispose();
  }
}

class Post extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Text("Post"),
    );
  }
}