Flutter生命周期与ViewModel管理插件an_lifecycle_viewmodel的使用

Flutter生命周期与ViewModel管理插件an_lifecycle_viewmodel的使用

使用说明

1lifecycle_viewmodel 是一个用于管理依赖于 anlifecycle 的 ViewModel 的包，类似于 Androidx ViewModel。

注意：该包将更名为 an_viewmodel。

1.1 准备生命周期环境

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  [@override](/user/override)
  Widget build(BuildContext context) {
    // 使用 LifecycleApp 包裹默认的 App
    return LifecycleApp(
      child: MaterialApp(
        title: 'ViewModel Demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        navigatorObservers: [
          // 使用 LifecycleNavigatorObserver.hookMode() 注册路由事件变化
          LifecycleNavigatorObserver.hookMode(),
        ],
        home: const MyHomePage(title: 'ViewModel Home Page'),
      ),
    );
  }
}

当前使用的 PageView 和 TabBarViewPageView 应该被替换为 LifecyclePageView 和 LifecycleTabBarView。或者你可以用 LifecyclePageViewItem 包裹项目。可以参考 anlifecycle 获取指导。

1.2 使用 viewModelsvm 来注入或获取现有的的 ViewModel

class ViewModelHome with ViewModel {
  final ValueNotifier<int> counter = ValueNotifier<int>(0);

  ViewModelHome(Lifecycle lifecycle) {
    /// 将 ValueNotifier 与 Lifecycle 关联，并在生命周期结束时自动调用 dispose。
    counter.bindLifecycle(lifecycle);
  }

  void incrementCounter() {
    counter.value++;
  }
}

class MyHomePage extends StatelessWidget {
  final String title;

  const MyHomePage({super.key, required this.title});

  [@override](/user/override)
  Widget build(BuildContext context) {
    // 在当前环境中获取 ViewModel
    final ViewModelHome viewModel = context.viewModels();

    return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const Text(
              'You have pushed the button this many times:',
            ),
            AnimatedBuilder(
              animation: viewModel.counter,
              builder: (_, __) =&gt; Text(
                '${viewModel.counter.value}',
                style: Theme.of(context).textTheme.headlineMedium,
              ),
            ),
          ],
        ),
      ),
      floatingActionButton: const HomeFloatingButton(),
    );
  }
}

/// 模拟子控件 可以在 state 中直接使用
class HomeFloatingButton extends StatefulWidget {
  const HomeFloatingButton({super.key});

  [@override](/user/override)
  State&lt;HomeFloatingButton&gt; createState() =&gt; _HomeFloatingButtonState();
}

class _HomeFloatingButtonState extends State&lt;HomeFloatingButton&gt; {
  // 在 state 中获取 ViewModel
  late final vm = viewModelsOfState&lt;ViewModelHome&gt;();

  [@override](/user/override)
  Widget build(BuildContext context) {
    return FloatingActionButton(
      onPressed: vm.incrementCounter,
      tooltip: 'Increment',
      child: const Icon(Icons.add),
    );
  }
}

额外信息

• 查看 anlifecycle
• 查看 cancelable
• 查看 an_lifecycle_cancellable

示例代码

import 'package:an_lifecycle_cancellable/an_lifecycle_cancellable.dart';
import 'package:an_lifecycle_viewmodel/an_lifecycle_viewmodel.dart';
import 'package:anlifecycle/anlifecycle.dart';
import 'package:flutter/material.dart';

void main() {
  /// 提前声明 ViewModelHome 的创建方式
  ViewModelProvider.addDefFactory2(ViewModelHome.new);
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  [@override](/user/override)
  Widget build(BuildContext context) {
    return LifecycleApp(
      child: MaterialApp(
        title: 'ViewModel Demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        navigatorObservers: [
          LifecycleNavigatorObserver.hookMode(),
        ],
        home: const MyHomePage(title: 'ViewModel Demo Home Page'),
      ),
    );
  }
}

class ViewModelHome with ViewModel {
  final ValueNotifier<int> counter = ValueNotifier<int>(0);

  ViewModelHome(Lifecycle lifecycle) {
    counter.bindLifecycle(lifecycle);
  }

  void incrementCounter() {
    counter.value++;
  }
}

class MyHomePage extends StatelessWidget {
  final String title;

  const MyHomePage({super.key, required this.title});

  [@override](/user/override)
  Widget build(BuildContext context) {
    // 获取当前环境下的 ViewModel
    final ViewModelHome viewModel = context.viewModels();

    // 也可使用 当前提供的构建工厂
    // final ViewModelHome viewModel =
    //     context.viewModels(factory2: ViewModelHome.new);

    // 从路由页来缓存 ViewModel
    // final ViewModelHome viewModel1 = context.viewModelsByRoute();

    // 从 App 全局来缓存 ViewModel
    // final ViewModelHome viewModel1 = context.viewModelsByApp();

    // 当还有引用时 下次获取依然是同一个 当没有任何引用的时候 会执行清理 vm
    // final ViewModelHome viewModel1 = context.viewModelsByRef();

    return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const Text(
              ' You have pushed the button this many times:',
            ),
            AnimatedBuilder(
              animation: viewModel.counter,
              builder: (_, __) =&gt; Text(
                '${viewModel.counter.value}',
                style: Theme.of(context).textTheme.headlineMedium,
              ),
            ),
          ],
        ),
      ),
      floatingActionButton: const HomeFloatingButton(),
    );
  }
}

/// 模拟子控件 可以在 state 中直接使用
class HomeFloatingButton extends StatefulWidget {
  const HomeFloatingButton({super.key});

  [@override](/user/override)
  State&lt;HomeFloatingButton&gt; createState() =&gt; _HomeFloatingButtonState();
}

class _HomeFloatingButtonState extends State&lt;HomeFloatingButton&gt; {
  // 获取 vm 可以在 state 中直接使用
  late final vm = viewModelsOfState&lt;ViewModelHome&gt;();

  [@override](/user/override)
  Widget build(BuildContext context) {
    return FloatingActionButton(
      onPressed: vm.incrementCounter,
      tooltip: 'Increment',
      child: const Icon(Icons.add),
    );
  }
}