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) {
Paint nodeStyle = Paint()..color = nestConfig.nodeColor;
if (cursor.hovering && (nodeInfoList.length == nestConfig.nodeCount)) {
// cursor just entered
// add cursor to nodeInfoList
nodeInfoList.add(NodeInfo(cursor.x, cursor.y, 0, 0));
} else if (cursor.hovering &&
(nodeInfoList.length != nestConfig.nodeCount)) {
// cursor already entered
// replace node
nodeInfoList.removeLast();
nodeInfoList.add(NodeInfo(cursor.x, cursor.y, 0, 0));
} else if (!cursor.hovering &&
(nodeInfoList.length != nestConfig.nodeCount)) {
nodeInfoList.removeLast();
}
// for every node,
for (var node in nodeInfoList) {
// move node
node.x += node.xVector;
node.y += node.yVector;
// change direction of node if it hits the wall
node.xVector *= (node.x > screenSize.width) || (node.x < 0) ? -1 : 1;
node.yVector *= (node.y > screenSize.height) || (node.y < 0) ? -1 : 1;
canvas.drawCircle(Offset(node.x, node.y), nestConfig.nodeSize, nodeStyle);
// TODO: paint line between each node if distance is less than specified amount
// compare this node to every other node to
// draw line and
// simulate gravity
for (var otherNode in nodeInfoList) {
if (identical(node, otherNode)) {
// print('Same node instance, skipping');
continue;
}
// print('Different node instance');
// DRAW LINE
double xDist = node.x - otherNode.x;
double yDist = node.y - otherNode.y;
double dist = sqrt(xDist * xDist + yDist * yDist); // pythagoras
if (dist < nestConfig.maxLineDist) {
nestConfig.lineColor = Colors.grey
.withAlpha(200 - (200 * dist ~/ nestConfig.maxLineDist));
Paint lineStyle = Paint()..color = nestConfig.lineColor;
canvas.drawLine(Offset(node.x, node.y),
Offset(otherNode.x, otherNode.y), lineStyle);
}
// SIMULATE GRAVITY
// at fixed interval only
// and only for mouse node
if (cursor.hovering &&
identical(node, nodeInfoList.last) &&
(dist < nestConfig.maxLineDist &&
dist > nestConfig.maxLineDist / 2)) {
otherNode.x += nestConfig.gravity * xDist;
otherNode.y += nestConfig.gravity * yDist;
}
}
}
}