Flutter widget that automatically resizes text to fit perfectly within its bounds.
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- Rich Text
AutoSizeText behaves exactly like a
Text. The only difference is that it resizes text to fit within its bounds.
AutoSizeText( 'The text to display', style: TextStyle(fontSize: 20), maxLines: 2, )
AutoSizeText needs bounded constraints to resize the text. More info here.
maxLines parameter works like you are used to with the
Text widget. If there is no
maxLines parameter specified, the
AutoSizeText only fits the text according to the available width and height.
AutoSizeText( 'A really long String', style: TextStyle(fontSize: 30), maxLines: 2, )
minFontSize & maxFontSize
AutoSizeText starts with
TextStyle.fontSize. It measures the resulting text and rescales it to fit within its bonds. You can however set the allowed range of the resulting font size.
minFontSize you can specify the smallest possible font size. If the text still doesn’t fit, it will be handled according to
overflow. The default
maxFontSize sets the largest possible font size. This is useful if the
TextStyle inherits the font size and you want to constrain it.
AutoSizeText( 'A really long String', style: TextStyle(fontSize: 30), minFontSize: 18, maxLines: 4, overflow: TextOverflow.ellipsis, )
You can synchronize the font size of multiple
AutoSizeText. They will fit their boundaries and all
AutoSizeText in the same group have the same size. That means they adjust their font size to the group member with the smallest effective font size.
Note: If a
AutoSizeText cannot adjust because of constraints like
minFontSize, it won’t have the same size as the other group members.
An instance of
AutoSizeGroup represents one group. Pass this instance to all
AutoSizeText you want to add to that group. You don’t have to care about disposing the group if it is no longer needed.
Important: Please don’t pass a new instance of
AutoSizeGroup every build. In other words, save the
AutoSizeGroup instance in a
var myGroup = AutoSizeGroup(); AutoSizeText( 'Text 1', group: myGroup, ); AutoSizeText( 'Text 2', group: myGroup, );
AutoSizeText will try each font size, starting with
TextStyle.fontSize until the text fits within its bounds.
stepGranularity specifies how much the font size is decreased each step. Usually, this value should not be below
1 for best performance.
AutoSizeText( 'A really long String', style: TextStyle(fontSize: 40), minFontSize: 10, stepGranularity: 10, maxLines: 4, overflow: TextOverflow.ellipsis, )
If you want to allow only specific font sizes, you can set them with
presetFontSizes is set,
stepGranularity will be ignored.
AutoSizeText( 'A really long String', presetFontSizes: [40, 20, 14], maxLines: 4, )
If the text is overflowing and does not fit its bounds, this widget is displayed instead. This can be useful to prevent text being too small to read.
AutoSizeText( 'A String tool long to display without extreme scaling or overflow.', maxLines: 1, overflowReplacement: Text('Sorry String too long'), )
You can also use Rich Text (like different text styles or links) with
AutoSizeText. Just use the
(which works exactly like the
The only thing you have to be aware of is how the font size calculation works: The
fontSize in the
AutoSizeText (or the inherited
fontSize if none is set) is used as reference.
AutoSizeText.rich( TextSpan(text: 'A really long String'), style: TextStyle(fontSize: 20), minFontSize: 5, )
The text will be at least 1/4 of its original size (5 / 20 = 1/4).
But it does not mean that all
TextSpans have at least font size
||Controls how one widget replaces another widget in the tree.|
||Sets the key for the resulting
||If non-null, the style to use for this text|
||The minimum text size constraint to be used when auto-sizing text.
Is being ignored if
||The maximum text size constraint to be used when auto-sizing text.
Is being ignored if
||The step size in which the font size is being adapted to constraints.|
||Predefines all the possible font sizes.
||Synchronizes the size of multiple
||How the text should be aligned horizontally.|
||The directionality of the text. This decides how
||Used to select a font when the same Unicode character can be rendered differently, depending on the locale.|
||Whether the text should break at soft line breaks.|
||Whether words which don’t fit in one line should be wrapped. Defaults to
||How visual overflow should be handled.|
||If the text is overflowing and does not fit its bounds, this widget is displayed instead.|
||The number of font pixels for each logical pixel. Also affects
||An optional maximum number of lines for the text to span.|
||An alternative semantics label for this text.|
Parameters marked with * behave exactly the same as in
AutoSizeText is really fast. In fact, you can replace all your
Text widgets with
Nevertheless you should not use an unreasonable high
fontSize in your
TextStyle. E.g. don’t set the
1000 if you know, that the text will never be larger than
If your font size has a very large range, consider increasing
AutoSizeText overflows or does not resize the text, you should check if it has constrained width and height.
Row( children: <Widget>[ AutoSizeText( 'Here is a very long text, which should be resized', maxLines: 1, ), ], )
Row and other widgets like
ListView do not constrain their children, the text will overflow.
You can fix this by constraining the
AutoSizeText. Wrap it with
Expanded in case of
Column or use a
SizedBox or another widget with fixed width (and height).
Row( children: <Widget>[ Expanded( // Constrains AutoSizeText to the width of the Row child: AutoSizeText( 'Here is a very long text, which should be resized', maxLines: 1, ) ), ], ) }
MinFontSize too large
AutoSizeText does not resize text below the
minFontSize which defaults to 12. This can happen very easily if you use
AutoSizeText.rich( TextSpan( text: 'Text that will not be resized correctly in some cases', style: TextStyle(fontSize: 200), ), )
This rich text does not have a style so it will fall back to the default style (probably
fontSize = 14). It has an implicit
minFontSize of 12 that means it can be resized to 86% of its original size at the most (14 -> 12). Just set
minFontSize = 0 or add
style: TextStyle(fontSize: 200) to the
Note: If you use the first option, you should also consider lowering
stepGranularity. Otherwise the steps of resizing will be very large.
AutoSizeText.rich( TextSpan( text: 'Text that will be resized correctly', style: TextStyle(fontSize: 200), ), minFontSize: 0, stepGranularity: 0.1, )