92 lines
3.0 KiB
Dart
92 lines
3.0 KiB
Dart
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import 'package:flutter/material.dart';
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import 'package:flutter/widgets.dart';
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// ------------------------------------------------------
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// author：AllenSu
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// date ：2021/4/18 11:23 AM
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// usage ：自定义 UnderlineTabIndicator
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// CSDN ：https://blog.csdn.net/qq_42351033
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// ------------------------------------------------------
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class CustomUnderlineTabIndicator extends Decoration {
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final BorderSide borderSide;
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final EdgeInsetsGeometry insets;
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final StrokeCap strokeCap; // 控制器的边角形状
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final double width; // 控制器的宽度
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const CustomUnderlineTabIndicator({
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this.borderSide = const BorderSide(width: 2, color: Colors.white),
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this.insets = EdgeInsets.zero,
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this.strokeCap: StrokeCap.square,
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this.width: 20,
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}) : assert(borderSide != null),
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assert(insets != null);
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@override
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Decoration lerpFrom(Decoration a, double t) {
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if (a is CustomUnderlineTabIndicator) {
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return CustomUnderlineTabIndicator(
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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 CustomUnderlineTabIndicator) {
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return CustomUnderlineTabIndicator(
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borderSide: BorderSide.lerp(borderSide, b.borderSide, t),
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insets: EdgeInsetsGeometry.lerp(insets, b.insets, t),
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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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@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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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 wantWidth = this.width;
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// 取中间坐标
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double cw = (indicator.left + indicator.right) / 2;
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// 这里是核心代码
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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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}
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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 CustomUnderlineTabIndicator 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
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._indicatorRectFor(rect, textDirection)
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.deflate(decoration.borderSide.width / 2);
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final Paint paint = decoration.borderSide.toPaint()
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..strokeCap = decoration.strokeCap; // 这里修改控制器边角的形状
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canvas.drawLine(indicator.bottomLeft, indicator.bottomRight, paint);
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}
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}
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