[Flutter] Creating, Importing & Using Dynamic Widgets from Other Files in a Flutter Application-优快云博客

本文详细介绍了在Flutter开发中如何创建并使用可复用的Widget，通过实例展示了如何将特定部分替换成可复用的Widget，以及如何传递参数给这些Widget，使得它们能在整个应用中重复使用。

In this lesson we’ll learn how to import widgets we’ve created in other files & use them in our project. We'll also look at how to create dynamic properties in our widgets in order to make them reusable across our application.

We have the CLI generate code:

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        brightness: Brightness.dark,
        primaryTextTheme: TextTheme(
          title: TextStyle(
            color: Colors.pinkAccent
          )
        ),
        primarySwatch: Colors.deepPurple,
        ),
      home: Scaffold(
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Container(
                width: 300,
                height: 300,
                alignment: Alignment.center,
                decoration: BoxDecoration(
                  color: Colors.black,
                  borderRadius: BorderRadius.circular(500)
                ),
                child: Text(
                  "Hello Flutter",
                  style: TextStyle(
                    color: Colors.red,
                    fontWeight: FontWeight.w500,
                    fontSize: 22.0
                  )
                )
              )
            ],
          )
        )
      ),
    );
  }
}

We want to replace the highlighted part with reusable Widget.

import 'package:flutter/material.dart';

class Greeting extends StatelessWidget {
  // To get passed in arg
  Greeting({
    @required this.greeting,
    this.color = Colors.green
  });
  // need to create a variable to hold greeting
  final String greeting;
  final Color color;
  @override
  Widget build(BuildContext context) {
    return Text(
      this.greeting,
      style: TextStyle(
        color: this.color,
        fontSize: 32
      )
    );
  }
}

Use it:

import 'package:flutter/material.dart';
import 'package:my_flutter_app/Greeting.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        brightness: Brightness.dark,
        primaryTextTheme: TextTheme(
          title: TextStyle(
            color: Colors.pinkAccent
          )
        ),
        primarySwatch: Colors.deepPurple,
        ),
      home: Scaffold(
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Container(
                width: 300,
                height: 300,
                alignment: Alignment.center,
                decoration: BoxDecoration(
                  color: Colors.black,
                  borderRadius: BorderRadius.circular(500)
                ),
                child: Greeting(greeting: "Hey you!", color: Colors.blue)
              )
            ],
          )
        )
      ),
    );
  }
}