How to set width as much as I need, but not more - flutter

Question

In appBar I have a container which is responsible for displaying text (it could be 5 chars or even 100). And I want to adjust width of container based on text. For example for 5 chars container should show text and should be a little bigger than text (I will add paddings later), but for 100 chars container should take all possible space and show text with dots.
Currently I have two solutions:
The first one (Without spacer() in tree) is expanding container always to the biggest possible width (like I said, I don't need this big container for short texts)
The second one (with spacer() in tree) is always displaying container with 1/3 width of appbar (Did someone know why it's always the same width? It's kind of interesting).
return Scaffold(
appBar: AppBar(
titleSpacing: 10,
centerTitle: false,
automaticallyImplyLeading: false,
title: SizedBox(
width: MediaQuery.of(context).size.width,
child: Row(
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
Container(height: 40, width: 40, color: Colors.amberAccent),
const SizedBox(width: 10),
const Text("Some Text"),
const SizedBox(width: 10),
Expanded(
child: Container(
color: Colors.purpleAccent,
height: 40,
child: const Center(
child: Text(
"text",
overflow: TextOverflow.ellipsis,
softWrap: true,
),
),
),
),
],
),
),
),
body: Container(),
);
So, how can I adjust width of this container to text inside?
Update:
I don't know if I explained it correctly, because your answers weren't related with my question 😁 So I will try again:
I want the last one container to take full possible width if text is long and for shorten texts just width to cover background behind text.
Here is long text: (It should be like that)
Here is short text: (Container should be smaller)

Answer 1

You should use constraints: BoxConstraints(maxWidth:), property of Container.
Please go with below code.
Container(
color: Colors.red,
padding: const EdgeInsets.all(20.0),
constraints: BoxConstraints(
maxWidth: MediaQuery.of(context).size.width * 0.7,
),
child: Text('Hello', style: TextStyle(color: Colors.black)),
),
Spacer(),
Flexible(
child: Container(
color: Colors.purpleAccent,
height: 40,
child: const Center(
child: Text(
"Long Textttttttttttttttttttt",
overflow: TextOverflow.ellipsis,
softWrap: true,
),
),
),
),
Your result will be like below screenshot.

Answer 2

I implement another text for checking dynamic width of container.
Container(
color: Colors.red,
padding: const EdgeInsets.all(20.0),
constraints: BoxConstraints(
maxWidth: MediaQuery.of(context).size.width * 0.7,
),
child: Text('Hello World', style: TextStyle(color: Colors.black)),
),
Spacer(),
Flexible(
child: Container(
color: Colors.purpleAccent,
height: 40,
child: const Center(
child: Text(
"Long Textttttttttttttttttttt",
overflow: TextOverflow.ellipsis,
softWrap: true,
),
),
),
),

Answer 3

For This You can Use :
Flexible Widget:
Example:
Flexible(
child: Container(
color: Colors.green,
)
),
or Wrap Widget :
Example :
Card(
margin: const EdgeInsets.only(top: 20.0),
child: Padding(
padding: const EdgeInsets.all(20.0),
child: Column(
children: <Widget>[
Text(
'Categories',
style: TextStyle(fontFamily: 'MonteSerrat', fontSize: 16.0),
),
Wrap(
children: <Widget>[
_checkBox('Gaming'),
_checkBox('Sports'),
_checkBox('Casual'),
_checkBox('21 +'),
_checkBox('Adult'),
_checkBox('Food'),
_checkBox('Club'),
_checkBox('Activities'),
_checkBox('Shopping')
],
)
],
),
));