paint method

@override void paint(Canvas canvas, Size size)

Called whenever the object needs to paint. The given Canvas has its coordinate space configured such that the origin is at the top left of the box. The area of the box is the size of the size argument.

Paint operations should remain inside the given area. Graphical operations outside the bounds may be silently ignored, clipped, or not clipped. It may sometimes be difficult to guarantee that a certain operation is inside the bounds (e.g., drawing a rectangle whose size is determined by user inputs). In that case, consider calling Canvas.clipRect at the beginning of paint so everything that follows will be guaranteed to only draw within the clipped area.

Implementations should be wary of correctly pairing any calls to Canvas.save/Canvas.saveLayer and Canvas.restore, otherwise all subsequent painting on this canvas may be affected, with potentially hilarious but confusing results.

To paint text on a Canvas, use a TextPainter.

To paint an image on a Canvas:

1. Obtain an ImageStream, for example by calling ImageProvider.resolve on an AssetImage or NetworkImage object.

2. Whenever the ImageStream's underlying ImageInfo object changes (see ImageStream.addListener), create a new instance of your custom paint delegate, giving it the new ImageInfo object.

3. In your delegate's paint method, call the Canvas.drawImage, Canvas.drawImageRect, or Canvas.drawImageNine methods to paint the ImageInfo.image object, applying the ImageInfo.scale value to obtain the correct rendering size.

Implementation

@override
void paint(Canvas canvas, Size size) {
  var center = Offset(size.width / 2, size.height / 2);
  var radius = min(size.width / 2, size.height / 2);

  // main circle
  Paint mainCircleBrush = Paint()..color = const Color(0xFF414673);

  // white circle in center
  Paint littleCircleBrush = Paint()..color = Colors.white;

  // border of clock
  Paint clockBorderBrush = Paint()
    ..color = Colors.white
    ..style = PaintingStyle.stroke
    ..strokeWidth = 10;

  // second hand of clock
  Paint secondBrush = Paint()
    ..color = const Color(0xFFF9B94B)
    ..style = PaintingStyle.stroke
    ..strokeCap = StrokeCap.round
    ..strokeWidth = 6;

  // minute hand of clock
  Paint minuteBrush = Paint()
    ..color = const Color(0xFF709BEC)
    ..style = PaintingStyle.stroke
    ..strokeCap = StrokeCap.round
    ..strokeWidth = 10;

  // hour hand of clock
  Paint hourBrush = Paint()
    ..color = const Color(0xFFE66C6C)
    ..style = PaintingStyle.stroke
    ..strokeCap = StrokeCap.round
    ..strokeWidth = 14;

  // draw main circle
  canvas.drawCircle(center, radius, mainCircleBrush);

  // draw clock border
  canvas.drawCircle(center, radius, clockBorderBrush);

  // draw hour hand
  var hourHandX = center.dx +
      radius *
          0.5 *
          cos((dateTime.hour % 12 + dateTime.minute / 60) * 30 * pi / 180);
  var hourHandY = center.dy +
      radius *
          0.5 *
          sin((dateTime.hour % 12 + dateTime.minute / 60) * 30 * pi / 180);
  canvas.drawLine(center, Offset(hourHandX, hourHandY), hourBrush);

  // draw minute hand
  var minuteHandX =
      center.dx + radius * 0.7 * cos(dateTime.minute * 6 * pi / 180);
  var minuteHandY =
      center.dy + radius * 0.7 * sin(dateTime.minute * 6 * pi / 180);
  canvas.drawLine(center, Offset(minuteHandX, minuteHandY), minuteBrush);

  // draw second hand
  var secondHandX =
      center.dx + radius * 0.9 * cos(dateTime.second * 6 * pi / 180);
  var secondHandY =
      center.dy + radius * 0.9 * sin(dateTime.second * 6 * pi / 180);
  canvas.drawLine(center, Offset(secondHandX, secondHandY), secondBrush);

  // draw center dot
  canvas.drawCircle(center, 10, littleCircleBrush);

  var dashBrush = Paint()
    ..color = const Color(0xFFEAECFF)
    ..style = PaintingStyle.stroke
    ..strokeCap = StrokeCap.round
    ..strokeWidth = 1;
  var centerX = size.width / 2;
  var outerCircleRadius = radius;
  var innerCircleRadius = radius - 14;
  for (double i = 0; i < 360; i += 12) {
    var x1 = centerX + outerCircleRadius * cos(i * pi / 180);
    var y1 = centerX + outerCircleRadius * sin(i * pi / 180);

    var x2 = centerX + innerCircleRadius * cos(i * pi / 180);
    var y2 = centerX + innerCircleRadius * sin(i * pi / 180);
    canvas.drawLine(Offset(x1, y1), Offset(x2, y2), dashBrush);
  }
}