Question

void _drawBackground(Canvas canvas, Rect shapeBounds, Rect avatarBounds) {
  //1
  final paint = Paint()..color = color;

  //2
  final backgroundPath = Path()
    ..moveTo(shapeBounds.left, shapeBounds.top) //3
    ..lineTo(shapeBounds.bottomLeft.dx, shapeBounds.bottomLeft.dy) //4
    ..arcTo(avatarBounds, -pi, pi, false) //5
    ..lineTo(shapeBounds.bottomRight.dx, shapeBounds.bottomRight.dy) //6
    ..lineTo(shapeBounds.topRight.dx, shapeBounds.topRight.dy) //7
    ..close(); //8

  //9
  canvas.drawPath(backgroundPath, paint);
}

flutter .. 中的这个运算符是什么，这个运算符有什么用途。

Answer 1

它是一种 dart 符号，允许您对 dart 对象 执行一系列操作，而不会影响对象的返回类型。它被称为 cascaded notation。

这个

List<String> titles = [];
titles.add(title1);
titles.add(title2);
titles.add(title3);

可以写成

 List<String> titles = []
 ..add(title1)
 ..add(title2)
 ..add(title3);

关于这个 .. 颤振/飞镖中的操作员

1 个答案: