QtQGraphicsScene中显⽰⽹格QGraphicsLineItem
直接添加 QGraphicsLineItem 类型的item即可，在scene中拖动或者缩放时候，⽹格不会变形和模糊。QPen pen2(QColor(128, 128, 128, 50));
for (float x = 0.5 * MAP_SCALE; x <= GRID_RANGE * MAP_SCALE; x += 0.5 * MAP_SCALE)
{
QLineF line(x, 0, x, GRID_RANGE * MAP_SCALE);
QGraphicsLineItem* tmpVertical = new QGraphicsLineItem(line);
tmpVertical->setPen(pen2);
gridItermVec.push_back(tmpVertical);
if (show_grid_)
{
addItem(tmpVertical);
}
}
//现在添加⽔平线
for (float y = 0.5 * MAP_SCALE; y <= GRID_RANGE * MAP_SCALE; y += 0.5 * MAP_SCALE)
{
QLineF line(0, y, GRID_RANGE * MAP_SCALE, y);
QGraphicsLineItem* tmpHorizontal = new QGraphicsLineItem(line);
tmpHorizontal->setPen(pen2);
gridItermVec.push_back(tmpHorizontal);
if (show_grid_)
{
addItem(tmpHorizontal);
}
}
显⽰效果如下
QPixmap
1. QGraphicsScene继承类中的构造函数
2.重写类的虚函数  void drawBackground(QPainter *painter, const QRectF &rect);
QPolygonF myPolygon1;
myPolygon1 << QPointF(0, 10) << QPointF(20, 10);
QPolygonF myPolygon2;
myPolygon2 << QPointF(10, 0) << QPointF(10, 20);
QPixmap pixmap(20, 20);
pixmap.fill(Qt::transparent);
QPainter painter(&pixmap);
QVector<qreal> dashes;//line style--虚线
qreal space = 2;
dashes << 2 << space << 2 << space;
QPen pen(Qt::lightGray, 1);
pen.setDashPattern(dashes);
pen.setWidth(1);
painter.setPen(pen);
painter.drawPolyline(myPolygon1);
painter.drawPolyline(myPolygon2);
this->setBackgroundBrush(pixmap);*/
或者如下代码
QPolygonF mypolygon1, mypolygon2;
mypolygon1 << QPointF(0, 5) << QPointF(10, 5);
mypolygon2 << QPointF(5, 0) << QPointF(5, 10);
QPixmap pix(10, 10);
pix.fill(Qt::transparent);
QPainter painter(&pix);
QVector <qreal> dashes;
dashes << 2 << 2 << 2 << 2;
QPen pen(Qt::darkCyan, 0.2);
pen.setDashPattern(dashes);
painter.setPen(pen);
painter.drawPolyline(mypolygon1);
painter.drawPolyline(mypolygon2);
this->setBackgroundBrush(pix);vertical怎么读
⼆者没有本质区别都是⽤Qpixmap 作为背景实现的栅格，但是在QGraphicsScene 中拖动⿏标时候会造成重影，⽬前不知道怎么消除。

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