Question

我正在尝试实现一个程序，当用户点击屏幕时，将从一个点到另一个点绘制线条。我有一个Polyline类，它是Freeform类的子类，它是Curve类的子类。 Curve超类的draw方法通常调用getPoint，它将获得该特定点的曲线的加权点。但是，对于Polyline的draw方法，我试图覆盖曲线类以获得用户点击的点（正如您所看到的，Polyline类的draw方法从不调用getPoint）。但是，当我调试代码时，我发现当我尝试绘制折线时仍然会调用getPoint。有什么建议吗？

class Curve {

public:
    virtual float2 getPoint(float t)=0;

    void draw(){

        glBegin(GL_LINE_STRIP);
        for (float i = 0; i < 1; i+=.01) {
            float2 point = getPoint(i);
            float x = point.x;
            float y = point.y;
            glVertex2d(x, y);

        }
        glEnd();
        }; 
    };

class Freeform : public Curve
{
protected:
    std::vector<float2> controlPoints;

public:
    virtual float2 getPoint(float t)=0;
    virtual void addControlPoint(float2 p)
    {
        controlPoints.push_back(p);
    }
    void drawControlPoints(){
        glBegin(GL_POINTS);
        for (float i = 0; i < controlPoints.size(); i++) {
            float2 point = controlPoints.at(i);
            float x = point.x;
            float y = point.y;
            glVertex2d(x, y);

        }
        glEnd();// draw points at control points
    }
};

class Polyline : public Freeform {
public:
    float2 getPoint(float t) {
        return float2(0.0, 0.0);
    }
    //we add a control point (in this case, control point is where mouse is clicked)
    void addControlPoint(float2 p)
    {
        controlPoints.push_back(p);
    }
    //trying to override Curve draw method
    void draw(){
        glBegin(GL_LINE_STRIP);
            for (float i = 0; i < controlPoints.size(); i++) {
            float2 point = controlPoints.at(i);
            float x = point.x;
            float y = point.y;
            glVertex2d(x, y);
        }
        glEnd();
    };
};

Answer 1

//trying to override Curve draw method

上面的评论几乎都说明了一切;您＆＃34;尝试＆＃34; 覆盖void Curve::draw ()，但由于先前未声明成员函数，因此无法执行此操作{{1} }。

解决方案

将virtual声明为void Curve::draw ()。
如果c++11或更高版本，请查看（并使用）关键字override。

发布覆盖绘制曲线的c ++类

1 个答案:

解决方案