如何使用 Flutter AnimationController 和 Transform 旋转图像？答案

【问题标题】：How to rotate an image using Flutter AnimationController and Transform?如何使用 Flutter AnimationController 和 Transform 旋转图像？
【发布时间】：2019-05-13 16:58:12
【问题描述】：

我有星星 png 图像，我需要使用 Flutter AnimationController 和 Transformer 旋转星星。我找不到任何图像旋转动画的文档或示例。

知道如何使用 Flutter AnimationController 和 Transform 旋转图像吗？

更新：

class _MyHomePageState extends State<MyHomePage>  with TickerProviderStateMixin {

  AnimationController animationController;

  @override
  void initState() {
    super.initState();
    animationController = new AnimationController(
      vsync: this,
      duration: new Duration(milliseconds: 5000),
    );
    animationController.forward();
    animationController.addListener(() {
      setState(() {
        if (animationController.status == AnimationStatus.completed) {
          animationController.repeat();
        }
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return new Container(
      alignment: Alignment.center,
      color: Colors.white,
      child: new AnimatedBuilder(
        animation: animationController,
        child: new Container(
          height: 80.0,
          width: 80.0,
          child: new Image.asset('images/StarLogo.png'),
        ),
        builder: (BuildContext context, Widget _widget) {
          return new Transform.rotate(
            angle: animationController.value,
            child: _widget,
          );
        },
      ),
    );
  }
}

【问题讨论】：

你能通过animationRotate初始化的代码吗？
我更新了我的代码。问题是它永远不会旋转 360 度。它旋转了大约 200 圈，然后重新开始，我可以看到它重新绘制了一个间隙。旋转 360 度时遇到问题，当停止时我需要立即重复，以便继续旋转变白停止...
更新了答案

标签： flutter dart flutter-layout transform flutter-animation

【解决方案1】：

完整示例（null 安全）：

按“开始”使星形图标旋转，直到您按“停止”。

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage>
    with SingleTickerProviderStateMixin {
  late AnimationController _controller;

  @override
  void initState() {
    _controller = AnimationController(
      duration: const Duration(milliseconds: 5000),
      vsync: this,
    );
    super.initState();
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Demo"),
      ),
      body: Center(
        child: Column(
          children: <Widget>[
            RotationTransition(
              turns: Tween(begin: 0.0, end: 1.0).animate(_controller),
              child: Icon(Icons.stars),
            ),
            ElevatedButton(
              child: Text("go"),
              onPressed: () => _controller.forward(),
            ),
            ElevatedButton(
              child: Text("reset"),
              onPressed: () => _controller.reset(),
            ),
          ],
        ),
      ),
    );
  }
}

分步指南：

首先，让您的小部件状态类实现SingleTickerProviderStateMixin。

其次，定义一个AnimationController 并且不要忘记处理它。如果您尚未使用 null-safe，请删除 late 关键字。

late AnimationController _controller;

@override
void initState() {
  _controller = AnimationController(
    duration: const Duration(milliseconds: 5000),
    vsync: this,
  );
  super.initState();
}

@override
void dispose() {
  _controller.dispose();
  super.dispose();
}

然后用RotationTransition 包裹你的Widget。

RotationTransition(
  turns: Tween(begin: 0.0, end: 1.0).animate(_controller),
  child: Icon(Icons.stars),
),

最后，调用AnimationController 上的方法来启动/停止动画。

运行一次动画，使用.forward
循环动画，使用.repeat
立即停止，使用.stop
停止并将其设置回原来的旋转，使用.reset
停止并为旋转值设置动画，使用.animateTo

【讨论】：

【解决方案2】：

这是我的旋转图像示例。我不知道 - 但也许它适合你

AnimationController rotationController;

@override
void initState() {
  rotationController = AnimationController(duration: const Duration(milliseconds: 500), vsync: this);
  super.initState();
}
//...
RotationTransition(
  turns: Tween(begin: 0.0, end: 1.0).animate(rotationController),
  child: ImgButton(...)
//...
rotationController.forward(from: 0.0); // it starts the animation

UPD - 如何解决Transform.rotate的问题

在您的情况下，一切都与您编写的完全一样 - 它将图像从 0.0 旋转到 1.0（它是 AnimationController 的默认参数）。对于整圈，您必须将上参数设置为 2 * pi（来自 math 包）

import 'dart:math';
//...
animationController = AnimationController(vsync: this, duration: Duration(seconds: 5), upperBound: pi * 2);

【讨论】：

如何在此处添加曲线
@codeboi 这里是答案stackoverflow.com/a/55365126/7130820

【解决方案3】：

屏幕截图（Null Safe）

完整代码：

import 'dart:math' as math;

class _FooPageState extends State<FooPage> with SingleTickerProviderStateMixin{
  late final AnimationController _controller = AnimationController(vsync: this, duration: Duration(seconds: 2))..repeat();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: AnimatedBuilder(
          animation: _controller,
          builder: (_, child) {
            return Transform.rotate(
              angle: _controller.value * 2 * math.pi,
              child: child,
            );
          },
          child: FlutterLogo(size: 200),
        ),
      ),
    );
  }
}

【讨论】：

如何沿 Y 轴旋转，有什么想法吗？

【解决方案4】：

在这里我一次旋转 3 张图像...保存在 assets 文件夹中的图像...如果您愿意，您也可以使用网络图像...我在这里以 3 种速度旋转 3 张图像...

import 'package:flutter/material.dart';
import 'package:fynd/services/auth.dart';
import 'dart:async';
import 'package:fynd/services/cons.dart';

class SplashScreen extends StatefulWidget {
  _SplashScreen createState() => new _SplashScreen();
}

class _SplashScreen extends State<StatefulWidget>
    with SingleTickerProviderStateMixin {
  AnimationController animationController;

  @override
  void initState() {
    super.initState();
    animationController = new AnimationController(
      vsync: this,
      duration: new Duration(seconds: 5),
    );

    animationController.repeat();
  }

  @override
  Widget build(BuildContext context) {

    return new Container(
      alignment: Alignment.center,
      color: Colors.white,
      child: new AnimatedBuilder(
        animation: animationController,
        child: new Container(
          decoration: BoxDecoration(
              image: DecorationImage(
                  image: AssetImage('assets/images/splash_circle3.png'))),
          child: new AnimatedBuilder(
            animation: animationController,
            child: new Container(
              decoration: BoxDecoration(
                  image: DecorationImage(
                      image: AssetImage('assets/images/splash_circle2.png'))),
              child: new AnimatedBuilder(
                  animation: animationController,
                  child: Container(
                      child: Container(
                    decoration: BoxDecoration(
                        image: DecorationImage(
                            image: AssetImage(
                                'assets/images/splash_circle1.png'))),
                  )),
                  builder: (BuildContext context, Widget _widget) {
                    return new Transform.rotate(
                      angle: animationController.value * 4,
                      child: _widget,
                    );
                  }),
            ),
            builder: (BuildContext context, Widget _widget) {
              return new Transform.rotate(
                angle: animationController.value * 5,
                child: _widget,
              );
            },
          ),
        ),
        builder: (BuildContext context, Widget _widget) {
          return new Transform.rotate(
            angle: animationController.value * 6,
            child: _widget,
          );
        },
      ),
    );
  }
}

【讨论】：

【解决方案5】：

在这里，我将动画生成器放在 Stack 中。然后你可以动画图像向右（顺时针）旋转和向左（逆时针）旋转。

import 'package:flutter/material.dart';
import 'package:fynd/services/auth.dart';
import 'dart:async';
import 'package:fynd/services/cons.dart';

class SplashScreen extends StatefulWidget {
  _SplashScreen createState() => new _SplashScreen();
}

class _SplashScreen extends State<StatefulWidget>
    with SingleTickerProviderStateMixin {
  AnimationController animationController;

  @override
  void initState() {
    super.initState();
    animationController = new AnimationController(
      vsync: this,
      duration: new Duration(seconds: 5),
    );

    animationController.repeat();

  }

  @override
  Widget build(BuildContext context)

    return new Container(
      alignment: Alignment.center,
      color: Colors.white,

      child: new Stack(children: <Widget>[

        new AnimatedBuilder(
          animation: animationController,
          child :Container(
            decoration: BoxDecoration(
                image: DecorationImage(image: AssetImage('assets/images/splash_circle3.png'),fit: BoxFit.cover)),

          ),
          builder: (BuildContext context, Widget _widget) {
            return new Transform.rotate(
              angle: animationController.value * 10,
              child: _widget,
            );
          },
        ),

       new AnimatedBuilder(
        animation: animationController,
        child: Container(
          decoration: BoxDecoration(
              image: DecorationImage(image: AssetImage('assets/images/splash_circle2.png'),fit: BoxFit.cover)),

        ),
        builder: (BuildContext context, Widget _widget) {
          return new Transform.rotate(
            angle: -animationController.value * 10,
            child: _widget,
          );
        },
       ),

        new AnimatedBuilder(
            animation: animationController,
           child: Container(
              decoration: BoxDecoration(
                  image: DecorationImage(image: AssetImage('assets/images/splash_circle1.png'), fit: BoxFit.cover)),
            ),
            builder: (BuildContext context, Widget _widget) {
              return new Transform.rotate(
                angle: animationController.value * 10,
                child: _widget,
              );
            }),

      ],),
    );
  }
}

【讨论】：

【解决方案6】：

class _MyHomePageState extends State<MyHomePage>  with TickerProviderStateMixin {

  AnimationController animationController;

  @override
  void initState() {
    super.initState();
    animationController = new AnimationController(
      vsync: this,
      duration: new Duration(milliseconds: 5000),
    );
    animationController.repeat();

  }

  @override
  Widget build(BuildContext context) {
    return new Container(
      alignment: Alignment.center,
      color: Colors.white,
      child: RotationTransition(
              child: Icon(Icons.refresh),
              turns: controller,
            )
    );
  }
}

【讨论】：

【解决方案7】：

_controller = AnimationController(duration: const Duration(seconds: 3), vsync: this); _animation = Tween(开始：0.0，结束：250.0).animate(_controller) ..addListener(() { setState(() {}); }) ..addStatusListener（（状态）{ if (state == AnimationStatus.completed) { 打印（“完成”）； } }); _controller.forward(); 新的 Future.delayed( const 持续时间（秒：5）， () => 导航器.push( 语境， MaterialPageRoute(builder: (context) => SignScreen()), ));

【讨论】：

【解决方案8】：

完整示例只需调用 ImageAnimateRotate(你的小部件)

class ImageAnimateRotate extends StatefulWidget {
  final Widget child;
  const ImageAnimateRotate({Key? key, required this.child}) : super(key: key);

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

class _ImageAnimateRotateState extends State<ImageAnimateRotate> with SingleTickerProviderStateMixin {
  late final AnimationController _controller;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(vsync: this, duration: Duration(seconds: 20))..repeat();
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: AnimatedBuilder(
        animation: _controller,
        builder: (_, child) {
          return Transform.rotate(
            angle: _controller.value * 2 * math.pi,
            child: child,
          );
        },
        child: widget.child,
      ),
    );
  }
}

【讨论】：