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final String explanation = |
'The screen forces the Center to be exactly the same size as the screen, ' |
'so the Center fills the screen.' |
'\n\n' |
'The Center tells the Container that it can be any size it wants, but not bigger than the screen.' |
'\n\n' |
'Since the Container has no child and no fixed size, it decides it wants to be as big as possible, so it fills the whole screen.' |
'\n\n' |
'But why does the Container decide that? ' |
'Simply because that\'s a design decision by those who created the Container widget. ' |
'It could have been created differently, and you have to read the Container documentation to understand how it behaves, depending on the circumstances. '; |
@override |
Widget build(BuildContext context) { |
return Center( |
child: Container(color: red), |
); |
} |
} |
class Example7 extends Example { |
const Example7({super.key}); |
@override |
final code = 'Center(\n' |
' child: Container(color: red\n' |
' child: Container(color: green, width: 30, height: 30)))'; |
@override |
final String explanation = |
'The screen forces the Center to be exactly the same size as the screen, ' |
'so the Center fills the screen.' |
'\n\n' |
'The Center tells the red Container that it can be any size it wants, but not bigger than the screen.' |
'Since the red Container has no size but has a child, it decides it wants to be the same size as its child.' |
'\n\n' |
'The red Container tells its child that it can be any size it wants, but not bigger than the screen.' |
'\n\n' |
'The child is a green Container that wants to be 30x30.' |
'\n\n' |
'Since the red `Container` has no size but has a child, it decides it wants to be the same size as its child. ' |
'The red color isn\'t visible, since the green Container entirely covers all of the red Container.'; |
@override |
Widget build(BuildContext context) { |
return Center( |
child: Container( |
color: red, |
child: Container(color: green, width: 30, height: 30), |
), |
); |
} |
} |
class Example8 extends Example { |
const Example8({super.key}); |
@override |
final code = 'Center(\n' |
' child: Container(color: red\n' |
' padding: const EdgeInsets.all(20),\n' |
' child: Container(color: green, width: 30, height: 30)))'; |
@override |
final String explanation = |
'The red Container sizes itself to its children size, but it takes its own padding into consideration. ' |
'So it is also 30x30 plus padding. ' |
'The red color is visible because of the padding, and the green Container has the same size as in the previous example.'; |
@override |
Widget build(BuildContext context) { |
return Center( |
child: Container( |
padding: const EdgeInsets.all(20), |
color: red, |
child: Container(color: green, width: 30, height: 30), |
), |
); |
} |
} |
class Example9 extends Example { |
const Example9({super.key}); |
@override |
final code = 'ConstrainedBox(\n' |
' constraints: BoxConstraints(\n' |
' minWidth: 70, minHeight: 70,\n' |
' maxWidth: 150, maxHeight: 150),\n' |
' child: Container(color: red, width: 10, height: 10)))'; |
@override |
final String explanation = |
'You might guess that the Container has to be between 70 and 150 pixels, but you would be wrong. ' |
'The ConstrainedBox only imposes ADDITIONAL constraints from those it receives from its parent.' |
'\n\n' |
'Here, the screen forces the ConstrainedBox to be exactly the same size as the screen, ' |
'so it tells its child Container to also assume the size of the screen, ' |
'thus ignoring its \'constraints\' parameter.'; |
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