paint method
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:
-
Obtain an ImageStream, for example by calling ImageProvider.resolve on an AssetImage or NetworkImage object.
-
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.
-
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 x = [];
var points = [];
var n = (size.width - 100);
for (int i = 0; i < myData['x'].length; i++) {
DateTime dt = DateTime.parse(myData['x'][i]);
x.add(dt.hour * 3600 + dt.minute * 60 + dt.second);
}
var x11 = [];
for (int i = 0; i < x.length; i++) {
x11.add(x[i]);
}
x11.sort();
for (int i = 0; i < x.length; i++) {
x[i] = (x[i] - x11[0]) *
(size.width - 50 - 50) /
(x11[x11.length - 1] - x11[0]) +
50;
}
var l1 = [0], r1 = [0];
for (int i = 0; i < myData['y1'].length; i++) {
l1.add(myData['y1'][i]);
r1.add(myData['y2'][i]);
}
for (int i = 0; i < x.length; i++) {
points.add(Offset(
(x[i]),
size.height -
50 -
myData['y'][i] *
(size.height + 50 - l1[l1.length - 1]) /
l1[l1.length - 1]));
}
var paint = Paint()
..color = Colors.black
..strokeWidth = 3.0
..strokeCap = StrokeCap.round;
var l = [], r = [];
for (int i = 0; i <= myData['y1'].length; i++) {
l.add(l1[i] * (size.height + 50 - l1[l1.length - 1]) / l1[l1.length - 1]);
r.add(r1[i] * (size.height + 50 - l1[l1.length - 1]) / l1[l1.length - 1]);
}
Offset p1 = Offset(50, size.height - 80 - (l[l.length - 1]));
Offset p3 = Offset(size.width - 50, size.height - 50);
Offset p2 = Offset(50, size.height - 50);
Offset p4 = Offset(size.width - 50, size.height - 50);
Offset p5 = Offset(size.width - 50, size.height - 80 - (l[l.length - 1]));
canvas.drawLine(p4, p5, paint);
canvas.drawLine(p1, p2, paint);
canvas.drawLine(p3, p2, paint);
var color = [
Colors.lightGreen,
Colors.orange,
Colors.grey,
Colors.blueGrey,
Colors.blue,
Colors.orangeAccent
];
for (int i = 0; i < l.length - 1; i++) {
Offset point1 =
Offset(50 + 1.5, size.height - 50 - (l[i] + l[i + 1]) / 2);
Offset point2 = Offset(
size.width - 50 - 1.5, size.height - 50 - (l[i] + l[i + 1]) / 2);
canvas.drawLine(
point1,
point2,
Paint()
..color = color[i]
..strokeWidth = (l[i + 1] - l[i]) * (size.height + 1) / size.height
..style = PaintingStyle.stroke);
} //colors
for (int i = 0; i < l.length - 1; i++) {
Offset point =
Offset(size.width / 2, size.height - 50 - (l[i] + l[i + 1]) / 2);
TextSpan span = TextSpan(
style: const TextStyle(color: Colors.black87),
text: "Zone " + ((i + 1).toString()));
TextPainter tp =
TextPainter(text: span, textDirection: TextDirection.ltr);
tp.layout();
tp.paint(canvas, point);
} //Zones
for (int i = 0; i < l.length; i++) {
Offset point1 = Offset(50 - 25, size.height - 50 - l[i]);
Offset point2 = Offset(size.width - 25, size.height - 50 - l[i]);
canvas.drawLine(point1, point2, paint);
} //region lines
for (int i = 0; i < l.length - 1; i++) {
TextSpan span1 = TextSpan(
style: const TextStyle(color: Colors.black),
text: (l1[i + 1]).toString());
TextPainter tp =
TextPainter(text: span1, textDirection: TextDirection.ltr);
tp.layout();
Offset point3 = Offset(50 / 2 - 5, size.height - 50 - (l[i + 1]));
tp.paint(canvas, point3);
//left points
TextSpan span2 = TextSpan(
style: const TextStyle(color: Colors.black),
text: (r1[i + 1]).toString());
TextPainter tp2 =
TextPainter(text: span2, textDirection: TextDirection.ltr);
tp2.layout();
Offset point4 =
Offset(size.width - 50 + 5, size.height - 50 - (l[i + 1]));
tp2.paint(canvas, point4);
//right points
}
for (int i = 0; i < points.length - 1; i++) {
if (points[i].dx <= n + 50) {
canvas.drawLine(
points[i],
points[i + 1],
Paint()
..color = Colors.red
..strokeWidth = 3.0
..strokeCap = StrokeCap.round);
}
} //graph
var pl = [], b = [], a = [], x1 = [];
var numOfPoints = 0;
for (var i = 25; i <= n + 50; i += 50) {
numOfPoints += 1;
}
var count = 0;
for (var i = 25;
i < n + 50 && count <= numOfPoints + 1;
i += 50, count += 1) {
x1.add(i);
a.add((((count) * (x.length - 1) / (numOfPoints - 1))).round());
} //x-points
for (int i = 0; i < a.length; i++) {
pl.insert(i, Offset(double.parse(x1[i].toString()), size.height - 50));
b.add(myData['x'][a[i]].substring(11, 16));
TextSpan span =
TextSpan(style: const TextStyle(color: Colors.black), text: b[i]);
TextPainter tp =
TextPainter(text: span, textDirection: TextDirection.ltr);
tp.layout();
Offset point = pl[i];
tp.paint(canvas, point);
} //x-labels
var text = [
myData['y1label'],
myData['y2label'],
myData['xlabel'] + '--->',
myData['xlabel'] + '--->'
];
var plots = [
Offset(50 / 2 - 5, size.height - 80 - (l[l.length - 1])),
Offset(size.width - 45, size.height - 80 - (l[l.length - 1])),
Offset(size.width - 50 - text[3].length * 8, size.height - 25),
Offset(50, size.height - 25)
];
for (int i = 0; i < text.length; i++) {
TextSpan span = TextSpan(
style:
const TextStyle(color: Colors.black, fontWeight: FontWeight.bold),
text: text[i]);
TextPainter tp =
TextPainter(text: span, textDirection: TextDirection.ltr);
tp.layout();
Offset point = plots[i];
tp.paint(canvas, point);
}
TextSpan span = TextSpan(
style: const TextStyle(
color: Colors.teal, fontWeight: FontWeight.bold, fontSize: 30),
text: myData['title']);
TextPainter tp = TextPainter(text: span, textDirection: TextDirection.ltr);
tp.layout();
Offset point = Offset(
(size.width - 50 - 50) / 2, size.height - 80 - (l[l.length - 1]) - 25);
tp.paint(canvas, point);
}