如何设置已定位文本块的背景颜色？ [英] How do I format the background color for a positioned block of text?

问题描述

我有一个定位的Text元素，它位于Stack中Image元素的顶部。我想为该Text元素应用简单的背景色，以便它像标题框一样框住文本：

I have a positioned Text element that sits on top of an Image element in a Stack. I'd like to apply a simple background color to that Text element, so that it frames the text like a caption box:

我可以通过在该Stack中插入另一个容器作为子容器来做到这一点。但每次文本字符串更改时，我都必须重新计算宽度，这是次优的。有更好的方法吗？

I can do this by inserting a Container as another positioned child in that Stack. But I'd have to recalculate the width every time the text string changes, which is sub-optimal. Is there a better way?

var stack = new Stack(
  children: <Widget>[
    new Image.asset ( // background photo
      "assets/texture.jpg",
      fit: ImageFit.cover,
      height: 600.0,
    ),
    new Positioned ( // headline
      child: new Container(
        decoration: new BoxDecoration (
          backgroundColor: Colors.black
        ),
      ),
      left: 0.0,
      bottom: 108.0,
      width: 490.0,
      height: 80.0,
    ),
    new Positioned (
      child: new Text (
        "Lorem ipsum dolor.",
        style: new TextStyle(
          color: Colors.blue[500],
          fontSize: 42.0,
          fontWeight: FontWeight.w900
        )
      ),
      left: 16.0,
      bottom: 128.0,
    )
  ]
);

推荐答案

只需将Text元素嵌套为子元素在具有BoxDecoration（即背景色）的容器中；容器将拉伸以适合内部的文本。另外，可以为该Container指定填充，这样就无需对框的宽度/高度进行硬编码。

Just nest the Text element as a child within the Container that has the BoxDecoration (i.e. background color); the Container will stretch to fit the Text inside. Additionally, one can specify padding for that Container, which eliminates the need to hardcode a width/height for the box.

var stack = new Stack(
  children: <Widget>[
    new Image.asset ( // background photo
      "assets/texture.jpg",
      fit: ImageFit.cover,
      height: 600.0,
    ),
    new Positioned ( // headline
      child: new Container(
        child: new Text (
          "Lorem ipsum dolor.",
          style: new TextStyle(
            color: Colors.blue[500],
            fontSize: 42.0,
            fontWeight: FontWeight.w900
          )
        ),
        decoration: new BoxDecoration (
          backgroundColor: Colors.black
        ),
        padding: new EdgeInsets.fromLTRB(16.0, 16.0, 16.0, 16.0),
      ),
      left: 0.0,
      bottom: 108.0,
    ),
  ]
);

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