颤动-创建以minHeight开始，增长到maxHeight的框的正确方法 [英] flutter - correct way to create a box that starts at minHeight, grows to maxHeight

问题描述

我有一个容器，我希望以最小尺寸开始，然后增长（如果用户添加内容时其内容增长）到最大尺寸，然后停止。

I have a container that I want to start off at a minimum size and grow (if its contents grow while user is adding content) to a maximum size, then stop.

正确的小部件似乎是ConstrainedBox，如下所示：

The correct widget for this seems to be ConstrainedBox, like so:

new ConstrainedBox(
  constraints: new BoxConstraints(
    minHeight: 35.0,
    maxHeight: 60.0,
  ),
  child: ...child with growing content (has default height 25.0)...
),

，但是，这会将框从maxHeight开始。

however, this starts the box off at the maxHeight.

我尝试使用hasBoundedHeight，但似乎无法为其构造正确的语法或在文档中找到示例。

I tried to use hasBoundedHeight, but can not seem to construct the correct syntax for it or find an example in documentation.

什么是最好的

推荐答案

没有从最大/最小尺寸开始的概念。

There's no notion of "Starts from max/min size".

问题是， ContrainedBox 只会为其子项添加约束。

The thing is, ContrainedBox only add constraints to it's child. But in the end, it doesn't pick a size.

如果您希望您的孩子达到minSize，则他们必须不消费。转换为 not 的宽度/高度为 double.INFINITY 。事实是 double.INFINITY 是许多小部件（包括 Container ）的默认值。

If you want your child to hit minSize, then they have to not expend. Which translate into not having a width/height of double.INFINITY. Fact is that double.INFINITY is the default value of many widgets, including Container.

另一方面，某些小部件，例如 DecoratedBox 的默认大小为0。
其中意味着这段代码：

On the other hand, some widgets such as DecoratedBox have a default size of 0. Which means that this code :

return new ConstrainedBox(
  constraints: new BoxConstraints(
    minHeight: 5.0,
    minWidth: 5.0,
    maxHeight: 30.0,
    maxWidth: 30.0,
  ),
  child: new DecoratedBox(
    decoration: new BoxDecoration(color: Colors.red),
  ),
);

将渲染一个5.0 * 5.0的红色方块。

Will render a 5.0*5.0 red square.

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