我创建了一个无状态的小部件,并且想要为它定义一个基线,以便我可以使用 Baseline 小部件 (https://docs.flutter.io/flutter/widgets/Baseline-class.html)。
我该如何做?
我创建了一个无状态的小部件,并且想要为它定义一个基线,以便我可以使用 Baseline 小部件 (https://docs.flutter.io/flutter/widgets/Baseline-class.html)。
我该如何做?
RenderBox
中进行操作,并实现computeDistanceToActualBaseline()
方法。ListTile
实现此处。您将看到_RenderListTile
RenderBox实现了上述方法,返回标题小部件的基线。 @override
double computeDistanceToActualBaseline(TextBaseline baseline) {
assert(title != null);
final BoxParentData parentData = title.parentData;
return parentData.offset.dy + title.getDistanceToActualBaseline(baseline);
}
import 'package:flutter/widgets.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/rendering.dart';
class BaselineBox extends SingleChildRenderObjectWidget {
const BaselineBox({Key key, @required this.baseline, Widget child})
: assert(baseline != null),
super(key: key, child: child);
final double baseline;
@override
RenderBaselineBox createRenderObject(BuildContext context) =>
new RenderBaselineBox(baseline: baseline);
@override
void updateRenderObject(
BuildContext context, RenderBaselineBox renderObject) {
renderObject.baseline = baseline;
}
@override
void debugFillProperties(DiagnosticPropertiesBuilder properties) {
super.debugFillProperties(properties);
properties.add(new DoubleProperty('baseline', baseline));
}
}
class RenderBaselineBox extends RenderProxyBox {
RenderBaselineBox({
RenderBox child,
@required double baseline,
}) : assert(baseline != null),
assert(baseline >= 0.0),
assert(baseline.isFinite),
_baseline = baseline,
super(child);
double get baseline => _baseline;
double _baseline;
set baseline(double value) {
assert(value != null);
assert(value >= 0.0);
assert(value.isFinite);
if (_baseline == value) return;
_baseline = value;
markNeedsLayout();
}
@override
double computeDistanceToActualBaseline(TextBaseline baselineType) {
return _baseline;
}
@override
void debugFillProperties(DiagnosticPropertiesBuilder properties) {
super.debugFillProperties(properties);
properties.add(new DoubleProperty('baseline', baseline));
}
}
AddBaseline
小部件,我可以像这样使用它:widget = AddBaseline(baseline:15.0, child: wiget);
- MarcGBaselineBox
的实现。 - chemamolinsfinal bool fromBottom;
。 - Blasanka