111、Flutter 实现动画颜色渐变效果

1、main.dart设置导航到登录界面

import 'package:flutter/material.dart';
import 'package:flash_chat/screens/welcome_screen.dart';
import 'package:flash_chat/screens/login_screen.dart';
import 'package:flash_chat/screens/registration_screen.dart';
import 'package:flash_chat/screens/chat_screen.dart';

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

class FlashChat extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(
        textTheme: TextTheme(
          body1: TextStyle(color: Colors.black54),
        ),
      ),
      initialRoute: WelcomeScreen.id,
      routes: {
        WelcomeScreen.id: (context) => WelcomeScreen(),
        LoginScreen.id: (context) => LoginScreen(),
        RegistrationScreen.id: (context) => RegistrationScreen(),
        ChatScreen.id: (context) => ChatScreen(),
      },
    );
  }
}

由上面可知默认导航到的是WelcomeScreen界面

2、welcome_screen.dart

 

AnimationController :设置特效的持续时间

ColorTween : 设置从哪个颜色渐变到哪个颜色

controller.forward();  :执行动画


backgroundColor: animation.value :将程序的背景颜色设置为animation.value

 

import 'package:flutter/material.dart';
import 'login_screen.dart';
import 'registration_screen.dart';

class WelcomeScreen extends StatefulWidget {
  static String id = 'welcome_screen';

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

class _WelcomeScreenState extends State
    with SingleTickerProviderStateMixin {
  AnimationController controller;
  Animation animation;

  @override
  void initState() {
    super.initState();

    controller = AnimationController(
        duration: Duration(seconds: 1), vsync: this); //AnimationController

    animation = ColorTween(begin: Colors.blueGrey, end: Colors.white)
        .animate(controller);

    controller.forward();

    controller.addListener(() {
      setState(() {});
      print(animation.value);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: animation.value,
      body: Padding(
        padding: EdgeInsets.symmetric(horizontal: 24.0),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            Row(
              children: [
                Hero(
                  tag: 'logo',
                  child: Container(
                    child: Image.asset('images/logo.png'),
                    height: 60.0,
                  ),
                ),
                Text(
                  'Falsh Chat',
                  style: TextStyle(
                    fontSize: 45.0,
                    fontWeight: FontWeight.w900,
                  ),
                ),
              ],
            ),
            SizedBox(
              height: 48.0,
            ),
            Padding(
              padding: EdgeInsets.symmetric(vertical: 16.0),
              child: Material(
                elevation: 5.0,
                color: Colors.lightBlueAccent,
                borderRadius: BorderRadius.circular(30.0),
                child: MaterialButton(
                  onPressed: () {
                    Navigator.pushNamed(context, LoginScreen.id);
                  },
                  minWidth: 200.0,
                  height: 42.0,
                  child: Text(
                    'Log In',
                  ),
                ),
              ),
            ),
            Padding(
              padding: EdgeInsets.symmetric(vertical: 16.0),
              child: Material(
                color: Colors.blueAccent,
                borderRadius: BorderRadius.circular(30.0),
                elevation: 5.0,
                child: MaterialButton(
                  onPressed: () {
                    Navigator.pushNamed(context, RegistrationScreen.id);
                  },
                  minWidth: 200.0,
                  height: 42.0,
                  child: Text(
                    'Register',
                  ),
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

效果:

颜色从蓝灰色渐变到白色