drawHelpItem method

Implementation

drawHelpItem(HelpItem item) {
  Paint paint = Paint()
    ..color = item.color
    ..style = PaintingStyle.stroke
    ..strokeWidth = 1;

  // 绘制箭头
  bool upArrow = item.endPoint!.dy < item.arrowPoint!.dy;
  Offset arrowPoint1 = Offset(item.arrowPoint!.dx - 5,
      upArrow ? item.arrowPoint!.dy - 5 : item.arrowPoint!.dy + 5);
  Offset arrowPoint2 = Offset(item.arrowPoint!.dx + 5,
      upArrow ? item.arrowPoint!.dy - 5 : item.arrowPoint!.dy + 5);
  this.drawLine(arrowPoint1, item.arrowPoint!, paint);
  this.drawLine(arrowPoint2, item.arrowPoint!, paint);

  // 绘制曲线
  Offset center1 = Offset(
      item.endPoint!.dx, (item.endPoint!.dy + item.arrowPoint!.dy) / 2);
  Offset center2 = Offset(
      item.arrowPoint!.dx, (item.endPoint!.dy + item.arrowPoint!.dy) / 2);
  Line line = Line(
      points: [item.endPoint!, center1, center2, item.arrowPoint!],
      smoothLevel: 20);
  Path path = PathExtra.line(line);

  this.drawPath(path, paint);

  // 绘制文本
  ui.ParagraphBuilder pb = ui.ParagraphBuilder(ui.ParagraphStyle());
  pb.pushStyle(ui.TextStyle(color: Colors.white, fontSize: 22));
  pb.addText(item.text!);
  pb.pop();
  ui.Paragraph pg = pb.build();
  pg.layout(ui.ParagraphConstraints(width: 200));
  print('item ${item.text} ${pg.width}');
  final textOffset = upArrow
      ? Offset(max(10, item.endPoint!.dx - 10), item.endPoint!.dy - 25)
      : Offset(max(10, item.endPoint!.dx - 10), item.endPoint!.dy);
  print('text offset $textOffset');
  this.drawParagraph(pg, textOffset);
}