画很多线很慢

Question

我想在3个表格上画很多线，但是当我调用这个方法时，它需要很多时间。 200 多行大约需要 1 秒。我做错了什么？

public void drawObjects()
{
    pAux = selectedPen;
    for (int i = 0; i < objects.Count; i++)
    {
        for(int ed = 0; ed < objects[i].getEdges().Count; ed++)
        {
            frontGraphics.DrawRectangle(recPen, (objects[i].getEdges()[ed].getPoint1().X + 332), -(objects[i].getEdges()[ed].getPoint1().Y - 170), 2, 2);
            rightGraphics.DrawRectangle(recPen, objects[i].getEdges()[ed].getPoint1().Z + 332, -(objects[i].getEdges()[ed].getPoint1().Y - 170), 2, 2);
            topGraphics.DrawRectangle(recPen, objects[i].getEdges()[ed].getPoint1().X + 332, -(objects[i].getEdges()[ed].getPoint1().Z - 170), 2, 2);

            if (objects[i].getEdges().Count > 0)
            {
                if (objects[i].selected == true)
                    pAux = selectedPen;
                else
                    pAux = linePen;
                frontGraphics.DrawLine(pAux, objects[i].getEdges()[ed].getPoint1().X + 332, -(objects[i].getEdges()[ed].getPoint1().Y -170), 
                                           objects[i].getEdges()[ed].getPoint2().X + 332, -(objects[i].getEdges()[ed].getPoint2().Y -170));
                rightGraphics.DrawLine(pAux, objects[i].getEdges()[ed].getPoint1().Z + 332, -(objects[i].getEdges()[ed].getPoint1().Y - 170),
                                            objects[i].getEdges()[ed].getPoint2().Z + 332, -(objects[i].getEdges()[ed].getPoint2().Y - 170));
                topGraphics.DrawLine(pAux, objects[i].getEdges()[ed].getPoint1().X + 332, -(objects[i].getEdges()[ed].getPoint1().Z - 170),
                                           objects[i].getEdges()[ed].getPoint2().X + 332, -(objects[i].getEdges()[ed].getPoint2().Z - 170));

            }
        }          
    }
}

Answer 1

不清楚您使用的是什么前端（WPF、WinForms），但您当前的代码可能会使用大量资源。 getEdges() and/or getPoint() 方法可能是昂贵的方法，并且您正在 多次调用这些方法.

如果有您要重用的方法的结果：将其存储在变量中。您的代码如下所示：

public void drawObjects()
{
    pAux = selectedPen;
    for (int i = 0; i < objects.Count; i++)
    {
        var currentObject = objects[i];
        var edges = currentObject.getEdges();

        for(int ed = 0; ed < edges.Count; ed++)
        {
            var currentEd = edges[ed];
            var edPoint1 = currentEd.getPoint1();
            var edPoint2 = currentEd.getPoint2();

            frontGraphics.DrawRectangle(recPen, (edPoint1.X + 332), -(edPoint1.Y - 170), 2, 2);
            rightGraphics.DrawRectangle(recPen, edPoint1.Z + 332, -(edPoint1.Y - 170), 2, 2);
            topGraphics.DrawRectangle(recPen, edPoint1.X + 332, -(edPoint1.Z - 170), 2, 2);

            pAux = currentObject.selected ? selectedPen : linePen;

            frontGraphics.DrawLine(pAux, edPoint1().X + 332, -(edPoint1().Y -170), edPoint2.X + 332, -(edPoint2.Y -170));
            rightGraphics.DrawLine(pAux, edPoint1.Z + 332, -(edPoint1.Y - 170), edPoint2.Z + 332, -(edPoint2.Y - 170));
            topGraphics.DrawLine(pAux, edPoint1.X + 332, -(edPoint1.Z - 170), edPoint2.X + 332, -(edPoint2.Z - 170));
        }          
    }
}

编辑：如@Hans Kesting所述，内循环中的这一行是多余的：

if (objects[i].getEdges().Count > 0)

自从您进入内部循环后，它将始终计算为 true。

PS: 请注意，这可能无法解决您所有的性能问题，但我相信这会有所帮助。

Answer 2

我用PICTURE BOX解决了这个问题，我画了一张位图，把位图设置为Picture box的图像。

画很多线很慢

Drawing a lot of lines is very slow

c#

forms

draw