59 lines
1.7 KiB
Dart
59 lines
1.7 KiB
Dart
import 'dart:math';
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import 'package:flutter/material.dart';
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class MyTabIndicationPainter extends CustomPainter {
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late Paint painter;
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late double dxTarget;
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late double dxEntry;
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late double radius;
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late double dy;
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final double indicatorWidth, xPadding, indicatorRadius, yPadding;
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final PageController? pageController;
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final Color? selectedBackground;
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MyTabIndicationPainter(
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{required this.indicatorWidth,
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required this.xPadding,
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required this.indicatorRadius,
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required this.yPadding,
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this.pageController,
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this.selectedBackground})
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: super(repaint: pageController) {
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dxTarget = indicatorWidth;
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dxEntry = xPadding;
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radius = indicatorRadius;
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dy = yPadding;
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painter = Paint()
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..color = selectedBackground!
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..style = PaintingStyle.fill;
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}
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@override
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void paint(Canvas canvas, Size size) {
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final pos = pageController!.position;
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double fullExtent =
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(pos.maxScrollExtent - pos.minScrollExtent + pos.viewportDimension);
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double pageOffset = pos.extentBefore / fullExtent;
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bool left2right = dxEntry < dxTarget;
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Offset entry = Offset(left2right ? dxEntry : dxTarget, dy);
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Offset target = Offset(left2right ? dxTarget : dxEntry, dy);
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Path path = Path();
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path.addArc(
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Rect.fromCircle(center: entry, radius: radius), 0.5 * pi, 1 * pi);
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path.addRect(Rect.fromLTRB(entry.dx, dy - radius, target.dx, dy + radius));
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path.addArc(
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Rect.fromCircle(center: target, radius: radius), 1.5 * pi, 1 * pi);
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canvas.translate(size.width * pageOffset, 0.0);
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canvas.drawPath(path, painter);
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}
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@override
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bool shouldRepaint(MyTabIndicationPainter oldDelegate) => true;
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}
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