import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter/foundation.dart';
// 默认高度从46改为40
const double _kTabHeight = 50.0;
const double _kTextAndIconTabHeight = 72.0;

class RoundUnderlineTabIndicator extends Decoration {
  /// Create an underline style selected tab indicator.
  ///
  /// The [borderSide] and [insets] arguments must not be null.
  const RoundUnderlineTabIndicator({
    this.borderSide = const BorderSide(width: 2.0, color: Colors.white),
    this.insets = EdgeInsets.zero,
  }) : assert(borderSide != null),
        assert(insets != null);

  /// The color and weight of the horizontal line drawn below the selected tab.
  final BorderSide borderSide;

  /// Locates the selected tab's underline relative to the tab's boundary.
  ///
  /// The [TabBar.indicatorSize] property can be used to define the
  /// tab indicator's bounds in terms of its (centered) tab widget with
  /// [TabIndicatorSize.label], or the entire tab with [TabIndicatorSize.tab].
  final EdgeInsetsGeometry insets;

  @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!);
  }
}

class _UnderlinePainter extends BoxPainter {
  _UnderlinePainter(this.decoration, VoidCallback onChanged)
      : assert(decoration != null),
        super(onChanged);

  final RoundUnderlineTabIndicator decoration;

  BorderSide get borderSide => decoration.borderSide;
  EdgeInsetsGeometry get insets => decoration.insets;

  Rect _indicatorRectFor(Rect rect, TextDirection textDirection) {
    assert(rect != null);
    assert(textDirection != null);
    final Rect indicator = insets.resolve(textDirection).deflateRect(rect);
//    return Rect.fromLTWH(
//      indicator.left,
//      indicator.bottom - borderSide.width,
//      indicator.width,
//      borderSide.width,
//    );
    //希望的宽度
    double wantWidth = 17;
    //取中间坐标
    double cw = (indicator.left + indicator.right) / 2;
    return Rect.fromLTWH(cw - wantWidth / 2,
        indicator.bottom - borderSide.width, wantWidth, borderSide.width);
  }

  @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 = _indicatorRectFor(rect!, textDirection!).deflate(borderSide.width / 2.0);
//    final Paint paint = borderSide.toPaint()..strokeCap = StrokeCap.square;
    // 改为圆角
    final Paint paint = borderSide.toPaint()..strokeCap = StrokeCap.round;
    canvas.drawLine(indicator.bottomLeft, indicator.bottomRight, paint);
  }
}






class VgTab extends StatelessWidget {
  /// Creates a material design [TabBar] tab.
  ///
  /// At least one of [text], [icon], and [child] must be non-null. The [text]
  /// and [child] arguments must not be used at the same time.
  const VgTab({
    Key? key,
    this.text,
    this.icon,
    this.child,
  }) : assert(text != null || child != null || icon != null),
        assert(!(text != null && null != child)), // TODO(goderbauer): https://github.com/dart-lang/sdk/issues/34180
        super(key: key);

  /// The text to display as the tab's label.
  ///
  /// Must not be used in combination with [child].
  final String? text;

  /// The widget to be used as the tab's label.
  ///
  /// Usually a [Text] widget, possibly wrapped in a [Semantics] widget.
  ///
  /// Must not be used in combination with [text].
  final Widget? child;

  /// An icon to display as the tab's label.
  final Widget? icon;

  Widget _buildLabelText() {
    return child ?? Text(text!, softWrap: false, overflow: TextOverflow.fade);
  }

  @override
  Widget build(BuildContext context) {
    assert(debugCheckHasMaterial(context));

    double height;
    Widget? label;
    if (icon == null) {
      height = _kTabHeight;
      label = _buildLabelText();
    } else if (text == null && child == null) {
      height = _kTabHeight;
      label = icon;
    } else {
      height = _kTextAndIconTabHeight;
      label = Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: <Widget>[
          Container(
            child: icon,
            margin: const EdgeInsets.only(bottom: 10.0),
          ),
          _buildLabelText(),
        ],
      );
    }

    return SizedBox(
      height: height,
      width: 30,
      child: Center(
        child: label,
        widthFactor: 1.0,
      ),
    );
  }

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
    super.debugFillProperties(properties);
    properties.add(StringProperty('text', text, defaultValue: null));
    properties.add(DiagnosticsProperty<Widget>('icon', icon, defaultValue: null));
  }
}