扑。如何使容器比屏幕宽？

Question

我正在尝试为页面控制器创建视差背景。为此，我需要创建一个比屏幕宽的背景图像。我把它放在这样的容器里：

@override
  Widget build(BuildContext context) {

    return Material(
      child: Stack(
        children: [
          Container(
              width: 4000,
              height:  250,
              decoration: BoxDecoration(
                  image: DecorationImage(
                      image: AssetImage('assets/images/pizza_bg.png'),
                      fit: BoxFit.cover,
                      repeat: ImageRepeat.noRepeat
                  )
              )
          ),
        ],
      ),
    );
  }

但问题是，无论我指定什么宽度，容器（当然还有图像）永远不会比屏幕宽。有可能吗？ p.s.我尝试使用 SizedBox 和 AspectRatio 小部件，它们都给出相同的结果

Answer 1

试试这个，作为一个选项

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Stack(
          children: [
            SingleChildScrollView(
              scrollDirection: Axis.horizontal,
              child: Container(
                width: 4000,
                height: 250,
                decoration: BoxDecoration(
                  image: DecorationImage(
                    image: AssetImage('assets/images/pizza_bg.png'),
                    fit: BoxFit.cover,
                    repeat: ImageRepeat.noRepeat,
                  ),
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

您也可以为用户禁用滚动并通过滚动控制器管理滚动位置

    SingleChildScrollView(
      scrollDirection: Axis.horizontal,
      physics: const NeverScrollableScrollPhysics(),
      controller: controller, // your ScrollController
      child: Container(
        width: 4000,
        height: 250,
        decoration: BoxDecoration(
          image: DecorationImage(
            image: AssetImage('images/pizza_bg.png'),
            fit: BoxFit.cover,
            repeat: ImageRepeat.noRepeat,
          ),
        ),
      ),
    ),

Answer 2

对于图像，您可以使用Transform.scale()，如documentation 中所示。使用您的示例：

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Stack(
          children: [
            Align(
              alignment: Alignment.center,
              child: Transform.scale(
                scale: 10.0,
                child: Container(
                  width: 400,
                  height: 25,
                  decoration: BoxDecoration(
                    image: DecorationImage(
                      image: AssetImage('assets/images/pizza_bg.png'),
                      fit: BoxFit.cover,
                      repeat: ImageRepeat.noRepeat,
                    ),
                  ),
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

如果要为比例设置动画，可以使用ScaleTransition()、explained in this page of the docs。例如：

/// Flutter code sample for ScaleTransition

// The following code implements the [ScaleTransition] as seen in the video
// above:

import 'package:flutter/material.dart';

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

/// This is the main application widget.
class MyApp extends StatelessWidget {
  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: _title,
      home: MyStatefulWidget(),
    );
  }
}

/// This is the stateful widget that the main application instantiates.
class MyStatefulWidget extends StatefulWidget {
  MyStatefulWidget({Key key}) : super(key: key);

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

/// This is the private State class that goes with MyStatefulWidget.
/// AnimationControllers can be created with `vsync: this` because of TickerProviderStateMixin.
class _MyStatefulWidgetState extends State<MyStatefulWidget>
    with TickerProviderStateMixin {
  AnimationController _controller;
  Animation<double> _animation;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: const Duration(seconds: 2),
      vsync: this,
    )..repeat(reverse: true);
    _animation = CurvedAnimation(
      parent: _controller,
      curve: Curves.fastOutSlowIn,
    );
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: ScaleTransition(
          scale: _animation,
          child: const Padding(
            padding: EdgeInsets.all(8.0),
            child: FlutterLogo(size: 150.0),
          ),
        ),
      ),
    );
  }
}

注意：为避免图像质量损失，请使用缩放后大小的图像或矢量图形作为来源。