【笔记】Flutter的自定义组件

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前言

Flutter的自定义组件学习笔记

自定义无状态组件

引入一个组件类

  • 无状态组件
  • 继承StatelessWidget接口，必须重写build()方法
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import 'package:flutter/material.dart';

void main() {
  runApp(MaterialApp(
    home: Scaffold(
      appBar: AppBar(
        title: const Text("文本内容"),
      ),
      body: App(),
    ),
  ));
}

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

  @override
  Widget build(BuildContext context) {
    return const Center(
      child: Text(
        "文本内容",
        textDirection: TextDirection.ltr,
      ),
    );
  }
}

引入多个组件类

  • 按照从上到下布局
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import 'package:flutter/material.dart';

void main() {
  runApp(MaterialApp(
    home: Scaffold(
      appBar: AppBar(
        title: Text("文本内容"),
      ),
      body: Column(
        children: [
          App(),
          App(),
        ],
      ),
    ),
  ));
}

自定义有状态组件

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import 'package:flutter/material.dart';

void main() {
  runApp(MaterialApp(
    home: Scaffold(
      appBar: AppBar(
        title: const Text("文本内容"),
      ),
      body: const App(),
    ),
  ));
}

class App extends StatefulWidget {
  const App({super.key});

  @override
  State<App> createState() => _AppState();
}

class _AppState extends State<App> {
  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

实现计数器自增

  • setState(() {})函数可以修改数据并重新渲染
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import 'package:flutter/material.dart';

void main() {
  runApp(MaterialApp(
    home: Scaffold(
      appBar: AppBar(
        title: const Text("文本内容"),
      ),
      body: const App(),
    ),
  ));
}

class App extends StatefulWidget {
  const App({super.key});

  @override
  State<App> createState() => _AppState();
}

class _AppState extends State<App> {

  int _num = 0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text("$_num", style: Theme.of(context).textTheme.headlineLarge),
            const SizedBox(height: 60),
            ElevatedButton(onPressed: () {
              setState(() {
                _num += 1;
              });
            }, child: const Text("+"))
          ],
        ),
      ),
    );
  }
}

完成

参考文献

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