controller : _controller, tabs : _tabs. map ((e) => Tab ( text : e)). toList (), isScrollable : true, indicator : RoundUnderlineTabIndicator ( borderSide : BorderSide ( width : 3 , color : xxxx), width : 43.0 , /// 下划线宽度 widthEqualTitle : false), ///下划线与label等宽

不指定宽度与lable等宽的使用：

 TabBar(
    controller: _controller,
    tabs: _tabs.map((e) => Tab(text: e)).toList(),
    isScrollable: true,
    indicatorSize: TabBarIndicatorSize.label,
    indicator: RoundUnderlineTabIndicator(
        borderSide: BorderSide(width: 3, color: xxxx),
源码（修改自带的UnderlineTabIndicator）：
import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';
class RoundUnderlineTabIndicator extends Decoration {
  const RoundUnderlineTabIndicator({
    this.borderSide = const BorderSide(width: 2.0, color: Colors.white),
    this.insets = EdgeInsets.zero,
    this.width = 0.0,
    this.widthEqualTitle = true,
  })  : assert(borderSide != null),
        assert(insets != null);
  final BorderSide borderSide;
  final EdgeInsetsGeometry insets;
  final double width;
  final bool widthEqualTitle;
  @override
  Decoration lerpFrom(Decoration a, double t) {
    if (a is UnderlineTabIndicator) {
      return UnderlineTabIndicator(
        borderSide: BorderSide.lerp(a.borderSide, borderSide, t),
        insets: EdgeInsetsGeometry.lerp(a.insets, insets, t),
    return super.lerpFrom(a, t);
  @override
  Decoration lerpTo(Decoration b, double t) {
    if (b is UnderlineTabIndicator) {
      return UnderlineTabIndicator(
        borderSide: BorderSide.lerp(borderSide, b.borderSide, t),
        insets: EdgeInsetsGeometry.lerp(insets, b.insets, t),
    return super.lerpTo(b, t);
  @override
  _UnderlinePainter createBoxPainter([VoidCallback onChanged]) {
    return _UnderlinePainter(this, onChanged);
  Rect _indicatorRectFor(Rect rect, TextDirection textDirection) {
    assert(rect != null);
    assert(textDirection != null);
    final Rect indicator = insets.resolve(textDirection).deflateRect(rect);
    if (widthEqualTitle) {
      return Rect.fromLTWH(
        indicator.left,
        indicator.bottom - borderSide.width,
        indicator.width,
        borderSide.width,
    } else {
      double w = (indicator.left + indicator.right) / 2;
      return Rect.fromLTWH(w - width / 2, indicator.bottom - borderSide.width, width, borderSide.width);
  @override
  Path getClipPath(Rect rect, TextDirection textDirection) {
    return Path()..addRect(_indicatorRectFor(rect, textDirection));
class _UnderlinePainter extends BoxPainter {
  _UnderlinePainter(this.decoration, VoidCallback onChanged)
      : assert(decoration != null),
        super(onChanged);
  final RoundUnderlineTabIndicator decoration;
  @override
  void paint(Canvas canvas, Offset offset, ImageConfiguration configuration) {
    assert(configuration != null);
    assert(configuration.size != null);
    final Rect rect = offset & configuration.size;
    final TextDirection textDirection = configuration.textDirection;
    final Rect indicator = decoration._indicatorRectFor(rect, textDirection).deflate(decoration.borderSide.width / 2.0);
    final Paint paint = decoration.borderSide.toPaint()..strokeCap = StrokeCap.round;
    canvas.drawLine(indicator.bottomLeft, indicator.bottomRight, paint);
欢迎关注：
  
分类：
 Android
 
标签：
 
Flutter
 
  
 

      安装掘金浏览器插件
     
多内容聚合浏览、多引擎快捷搜索、多工具便捷提效、多模式随心畅享，你想要的，这里都有！
 前往安装
     
 

        Android，Flutter @ JD
         4,684