getEffectiveTextDirection method Null safety
- BuildContext context
The value to pass to RenderFlex.textDirection.
This value is derived from the textDirection property and the ambient
Directionality. The value is null if there is no need to specify the
text direction. In practice there's always a need to specify the direction
except for vertical flexes (e.g. Columns) whose crossAxisAlignment is
not dependent on the text direction (not start
or end
). In particular,
a Row always needs a text direction because the text direction controls
its layout order. (For Columns, the layout order is controlled by
verticalDirection, which is always specified as it does not depend on an
inherited widget and defaults to VerticalDirection.down.)
This method exists so that subclasses of Flex that create their own render objects that are derived from RenderFlex can do so and still use the logic for providing a text direction only when it is necessary.
Implementation
@protected
TextDirection? getEffectiveTextDirection(BuildContext context) {
return textDirection ?? (_needTextDirection ? Directionality.maybeOf(context) : null);
}