77 lines
2.5 KiB
Dart
77 lines
2.5 KiB
Dart
import 'package:flutter/material.dart';
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import 'package:flutter/widgets.dart';
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class MyUnderlineTabIndicator extends Decoration {
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const MyUnderlineTabIndicator({
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this.borderSide = const BorderSide(width: 2.0, color: Colors.white),
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this.insets = EdgeInsets.zero, required this.wantWidth,
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}) : assert(borderSide != null),
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assert(insets != null);
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final BorderSide borderSide;
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final EdgeInsetsGeometry insets;
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final double wantWidth;
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@override
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Decoration? lerpFrom(Decoration? a, double t) {
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if (a is MyUnderlineTabIndicator) {
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return MyUnderlineTabIndicator(
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wantWidth:5,
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borderSide: BorderSide.lerp(a.borderSide, borderSide, t),
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insets: EdgeInsetsGeometry.lerp(a.insets, insets, t)!,
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);
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}
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return super.lerpFrom(a, t);
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}
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@override
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Decoration? lerpTo(Decoration? b, double t) {
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if (b is MyUnderlineTabIndicator) {
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return MyUnderlineTabIndicator(
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borderSide: BorderSide.lerp(borderSide, b.borderSide, t),
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insets: EdgeInsetsGeometry.lerp(insets, b.insets, t)!, wantWidth: 5,
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);
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}
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return super.lerpTo(b, t);
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}
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@override
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_UnderlinePainter createBoxPainter([ VoidCallback? onChanged ]) {
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return _UnderlinePainter(this, onChanged);
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}
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Rect _indicatorRectFor(Rect rect, TextDirection textDirection) {
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assert(rect != null);
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assert(textDirection != null);
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final Rect indicator = insets.resolve(textDirection).deflateRect(rect);
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//希望的宽度
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double cw = (indicator.left + indicator.right) / 2;
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return Rect.fromLTWH(cw - wantWidth / 2,
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indicator.bottom - borderSide.width, wantWidth, borderSide.width);
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}
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@override
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Path getClipPath(Rect rect, TextDirection textDirection) {
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return Path()..addRect(_indicatorRectFor(rect, textDirection));
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}
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}
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class _UnderlinePainter extends BoxPainter {
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_UnderlinePainter(this.decoration, VoidCallback? onChanged)
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: assert(decoration != null),
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super(onChanged);
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final MyUnderlineTabIndicator decoration;
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@override
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void paint(Canvas canvas, Offset offset, ImageConfiguration configuration) {
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assert(configuration != null);
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assert(configuration.size != null);
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final Rect rect = offset & configuration.size!;
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final TextDirection textDirection = configuration.textDirection!;
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final Rect indicator = decoration._indicatorRectFor(rect, textDirection).deflate(decoration.borderSide.width / 2.0);
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final Paint paint = decoration.borderSide.toPaint()..strokeCap = StrokeCap.round;
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canvas.drawLine(indicator.bottomLeft, indicator.bottomRight, paint);
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}
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}
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