如何更改OutlinedTextField的边框宽度？

要更改OutlinedTextField的边框宽度，您需要自定义边框和背景绘制

方法一：使用ShapeBorder自定义边框

创建一个自定义ShapeBorder类，重写paint方法，以自定义边框宽度和颜色。

import 'package:flutter/material.dart';

class CustomBorder extends ShapeBorder {
  final double borderWidth;
  final Color borderColor;

  CustomBorder({required this.borderWidth, required this.borderColor});

  @override
  EdgeInsetsGeometry get dimensions => EdgeInsets.zero;

  @override
  Path getInnerPath(Rect rect, {TextDirection? textDirection}) => Path();

  @override
  Path getOuterPath(Rect rect, {TextDirection? textDirection}) => Path();

  @override
  void paint(Canvas canvas, Rect rect, {TextDirection? textDirection}) {
    final Paint paint = Paint()
      ..color = borderColor
      ..style = PaintingStyle.stroke
      ..strokeWidth = borderWidth;

    final BorderRadius borderRadius = BorderRadius.circular(4.0);
    final Rect borderRect = borderRadius.resolve(rect);

    canvas.drawRRect(borderRect, paint);
  }
}

在OutlinedTextField中，设置decoration属性为InputDecoration，并自定义border属性。

OutlinedTextField(
  decoration: InputDecoration(
    border: CustomBorder(borderWidth: 2.0, borderColor: Colors.blue),
  ),
);

方法二：使用BoxDecoration自定义背景和边框

OutlinedTextField(
  decoration: InputDecoration(
    border: OutlineInputBorder(
      borderRadius: BorderRadius.circular(4.0),
      borderSide: BorderSide(width: 2.0, color: Colors.blue), // 设置边框宽度和颜色
    ),
  ),
);

这两种方法都可以更改OutlinedTextField的边框宽度。第一种方法允许您完全自定义边框，包括使用不规则形状。第二种方法则更简单，适用于更常见的矩形边框。选择哪种方法取决于您的需求。