Flutter Container 变换（动画包）

Question

随机地，当我看到 flutter 包和库时，我发现了flutteranimations 包，并且我看到，有一个非常有用的动画Gmail，例如具有搜索导航动画的 Android 应用程序。要理解我的意思，您可以查看此链接，第 4 号动画

我在 github 上的存储库中查看了此包的源文件夹，但我找不到此动画的示例实现，并且我不确定是否有示例代码，有人可以帮助我如何使用它吗Container transform？

Answer 1

动画包提供OpenContainer小部件。

该小部件有 2 个构建器：openBuilder closedBuilder.
ClosedBuilder返回用户在打开之前和关闭小部件之后看到的小部件，在流动示例中是SearchBar。
OpenBuilder返回用户打开关闭的小部件后显示的页面，在流动示例中为SearchPage。

打开和关闭操作通过调用回调触发：openContainer, closeContainer。

import 'package:animations/animations.dart';
import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        brightness: Brightness.light,
        primarySwatch: Colors.blue,
        scaffoldBackgroundColor: Colors.white,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key key}) : super(key: key);

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

class _MyHomePageState extends State<MyHomePage> {
  String searchString;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: Padding(
          padding: const EdgeInsets.all(15.0),
          child: OpenContainer<String>(
            openBuilder: (_, closeContainer) => SearchPage(closeContainer),
            onClosed: (res) => setState(() {
              searchString = res;
            }),
            tappable: false,
            closedBuilder: (_, openContainer) => SearchBar(
              searchString: searchString,
              openContainer: openContainer,
            ),
          ),
        ),
      ),
    );
  }
}

class SearchBar extends StatelessWidget {
  const SearchBar(
      {Key key, @required this.searchString, @required this.openContainer})
      : super(key: key);

  final String searchString;
  final VoidCallback openContainer;
  @override
  Widget build(BuildContext context) {
    return Material(
      elevation: 3,
      borderRadius: BorderRadius.circular(5),
      child: InkWell(
        onTap: openContainer,
        child: Container(
          padding: EdgeInsets.all(10),
          color: Colors.white,
          child: Row(
            children: [
              Icon(Icons.search),
              SizedBox(width: 10),
              searchString != null
                  ? Expanded(child: Text(searchString))
                  : Spacer(),
              Icon(Icons.mic),
            ],
          ),
        ),
      ),
    );
  }
}

class SearchPage extends StatelessWidget {
  const SearchPage(
    this.onClose, {
    Key key,
  }) : super(key: key);

  final void Function({String returnValue}) onClose;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Container(
              padding: EdgeInsets.symmetric(horizontal: 10),
              decoration: BoxDecoration(
                boxShadow: [
                  BoxShadow(
                    offset: Offset(0, 2),
                    spreadRadius: 0,
                    blurRadius: 1,
                    color: Colors.black26,
                  )
                ],
                color: Colors.white,
              ),
              child: Row(
                children: [
                  IconButton(
                    icon: Icon(Icons.arrow_back),
                    onPressed: onClose,
                  ),
                  Spacer(),
                  Icon(Icons.mic),
                ],
              ),
            ),
            Padding(
              padding: const EdgeInsets.all(20.0),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  OutlineButton(
                    onPressed: () => onClose(returnValue: 'Flutter'),
                    child: Text('Search: "Flutter"'),
                  ),
                  OutlineButton(
                    onPressed: () => onClose(returnValue: 'Rabbit'),
                    child: Text('Search: "Rabbit"'),
                  ),
                  OutlineButton(
                    onPressed: () => onClose(returnValue: 'What is the Matrix'),
                    child: Text('Search: "What is the Matrix"'),
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }
}