如何在Flutter中拉伸图像以适合整个背景（高度100％x宽度100％）？ [英] How do I stretch an image to fit the whole background (100% height x 100% width) in Flutter?

问题描述

我的图像与设备屏幕的纵横比不匹配。我想拉伸图像以使其完全填满屏幕，并且不想裁剪图像的任何部分。

I have an image that doesn't match the aspect ratio of my device's screen. I want to stretch the image so that it fully fills the screen, and I don't want to crop any part of the image.

CSS具有百分比的概念，因此我可以将高度和宽度设置为100％。但是Flutter似乎没有这个概念，仅对高度和宽度进行硬编码是很不好的，所以我被卡住了。

CSS has the concept of percentages, so I could just set height and width to 100%. But it doesn't seem like Flutter has that concept, and it's bad to just hard code the height and width, so I'm stuck.

这就是我所拥有的（我正在使用堆栈，因为图像的前景中有东西）：

Here's what I have (I'm using a Stack since I have something in the foreground of the image):

Widget background = new Container(
  height: // Not sure what to put here!
  width: // Not sure what to put here!
  child: new Image.asset(
    asset.background,
    fit: BoxFit.fill, // I thought this would fill up my Container but it doesn't
  ),
);

return new Stack(
  children: <Widget>[
    background,
    foreground,
  ],
);

推荐答案

要使图像填充其父级，只需将其包装放入 FittedBox ：

To make an Image fill its parent, simply wrap it into a FittedBox:

FittedBox(
  child: Image.asset('foo.png'),
  fit: BoxFit.fill,
)

FittedBox 在这里将拉伸图像以填充空间。
（请注意，此功能以前是由 BoxFit.fill 提供的，但与此同时，API进行了更改，使得 BoxFit 不再提供此功能。 FittedBox 应该可以直接替换，而无需更改构造函数参数。）

FittedBox here will stretch the image to fill the space. (Note that this functionality used to be provided by BoxFit.fill, but the API has meanwhile changed such that BoxFit no longer provides this functionality. FittedBox should work as a drop-in replacement, no changes need to be made to the constructor arguments.)

或者，对于复杂的装饰，可以使用 Container 代替图片 –并使用装饰 / foregroundDecoration 字段。

Alternatively, for complex decorations you can use a Container instead of an Image – and use decoration/foregroundDecoration fields.

要使容器成为其父对象，它应该：

To make the Container will its parent, it should either:

• 没有孩子


• 具有 alignment 属性而不是 null

• have no child
• have alignment property not null

在此示例中，将两个图像和一个 Text 合并为一个示例容器，同时采用其父级宽度/高度的100％：

Here's an example that combines two images and a Text in a single Container, while taking 100% width/height of its parent:

Container(
  foregroundDecoration: const BoxDecoration(
    image: DecorationImage(
        image: NetworkImage(
            'https://p6.storage.canalblog.com/69/50/922142/85510911_o.png'),
        fit: BoxFit.fill),
  ),
  decoration: const BoxDecoration(
    image: DecorationImage(
        alignment: Alignment(-.2, 0),
        image: NetworkImage(
            'http://www.naturerights.com/blog/wp-content/uploads/2017/12/Taranaki-NR-post-1170x550.png'),
        fit: BoxFit.cover),
  ),
  alignment: Alignment.bottomCenter,
  padding: EdgeInsets.only(bottom: 20),
  child: Text(
    "Hello World",
    style: Theme.of(context)
        .textTheme
        .display1
        .copyWith(color: Colors.white),
  ),
),

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