我們知道flutter框架中有StatefulWidget的存在辖所，而它對(duì)應(yīng)的State有自己的一套生命周期磨德。具體可查閱State生命周期。它并不能完全滿足類似iOS中UIViewController生命周期的需求酥宴。慶幸的是RouteObserver這個(gè)類可以幫我們實(shí)現(xiàn)您觉。

RouteObserver詳解本篇文章就不說了，網(wǎng)上資料一大把肆糕。但是RouteObserver使用起來比較繁瑣在孝，每一個(gè)需要監(jiān)聽路由變化的Widget都需要去實(shí)現(xiàn)接口RouteAware。并重寫didChangeDependencies方法(在其中添加訂閱消息的代碼)和dispose方法（在其中取消訂閱）私沮。

所以我將這個(gè)功能封裝成了一個(gè)Widget：CWRouteListenWidget仔燕，使用起來非常方便，只需在build方法中涨享，將你需要監(jiān)聽的Widget作為CWRouteListenWidget的子Widget即可厕隧。

示例代碼如下：

• 首先在創(chuàng)建MaterialApp的地方注冊(cè)navigatorObservers
  

• 在需要監(jiān)聽的widget中使用：

class TempPage extends StatelessWidget {

  const TempPage({Key? key}) : super(key: key);

  void _appear(CWRouteChangeType type) {
    switch (type) {
      case CWRouteChangeType.push:
        debugPrint("從其他頁面push到當(dāng)前頁面");
        break;
      case CWRouteChangeType.pop:
        debugPrint("從其他頁面返回到當(dāng)前頁面");
        break;
    }
  }

  void _disappear(CWRouteChangeType type) {
    switch (type) {
      case CWRouteChangeType.push:
        debugPrint("從當(dāng)前頁面push到其他頁面");
        break;
      case CWRouteChangeType.pop:
        debugPrint("從當(dāng)前頁面返回到其他頁面");
        break;
    }
  }

  @override
  Widget build(BuildContext context) {
    return CWRouteListenWidget(
      appearHandler: _appear,
      disappearHandler: _disappear,
      child: Scaffold(
        appBar: AppBar(
          title: const Text("test"),
        ),
        body: const Center(
          child: Text("content"),
        ),
      ),
    );
  }
}

• 其中appearHandler類似iOS中的viewWillAppear||viewDidAppear
• 其中disappearHandler類似iOS中的viewWillDisappear||viewDidDisappear

CWRouteListenWidget源碼如下：

import 'package:flutter/material.dart';

// 路由操作枚舉
enum CWRouteChangeType {
  push,
  pop
}

// 路由監(jiān)聽widget
class CWRouteListenWidget extends StatefulWidget {

  static RouteObserver<PageRoute> routeObserver = RouteObserver<PageRoute>();

  final Widget child;

  // 當(dāng)前頁面展示時(shí)的回調(diào)
  final Function(CWRouteChangeType)? appearHandler;

  // 當(dāng)前頁面消失時(shí)的回調(diào)
  final Function(CWRouteChangeType)? disappearHandler;

  // 構(gòu)造方法
  const CWRouteListenWidget({Key? key, required this.child, this.appearHandler, this.disappearHandler}) : super(key: key);

  @override
  _CWRouteListenWidgetState createState() => _CWRouteListenWidgetState();
}

class _CWRouteListenWidgetState extends State<CWRouteListenWidget> with RouteAware {

  @override
  void didChangeDependencies() {
    ModalRoute? route = ModalRoute.of(context);
    if (route != null) {
      CWRouteListenWidget.routeObserver.unsubscribe(this);
      // 注冊(cè)監(jiān)聽
      CWRouteListenWidget.routeObserver.subscribe(this, route as PageRoute);
    }
    super.didChangeDependencies();
  }

  @override
  void dispose() {
    // 移除監(jiān)聽
    CWRouteListenWidget.routeObserver.unsubscribe(this);
    super.dispose();
  }

  @override
  void didPush() {
    if (widget.appearHandler != null) {
      widget.appearHandler!(CWRouteChangeType.push);
    }
    super.didPush();
  }

  @override
  void didPop() {
    if (widget.disappearHandler != null) {
      widget.disappearHandler!(CWRouteChangeType.pop);
    }
    super.didPop();
  }

  @override
  void didPushNext() {
    if (widget.disappearHandler != null) {
      widget.disappearHandler!(CWRouteChangeType.push);
    }
    super.didPushNext();
  }

  @override
  void didPopNext() {
    if (widget.appearHandler != null) {
      widget.appearHandler!(CWRouteChangeType.pop);
    }
    super.didPopNext();
  }

  @override
  Widget build(BuildContext context) {
    return widget.child;
  }
}