class Point
{
public:
int x;
int y;
};
class Line
{
public:
Point start;
Point end;
Line(const Point& start, const Point& end){
this->start = start;
this->end = end;
}
};
class Rect
{
public:
Point leftUp;
int width;
int height;
Rect(const Point& leftUp, int width, int height){
this->leftUp = leftUp;
this->width = width;
this->height = height;
}
};
//增加
class Circle{
};
class MainForm : public Form
{
private:
Point p1;
Point p2;
vector<Line> lineVector;
vector<Rect> rectVector;
//改变
vector<Circle> circleVector;
public:
MainForm()
{
//...
}
protected:
virtual void OnMouseDown(const MouseEventArgs& e);
virtual void OnMouseUp(const MouseEventArgs& e);
virtual void OnPaint(const PaintEventArgs& e);
};
void MainForm::OnMouseDown(const MouseEventArgs& e){
p1.x = e.X;
p1.y = e.Y;
//...
Form::OnMouseDown(e);
}
void MainForm::OnMouseUp(const MouseEventArgs& e){
p2.x = e.X;
p2.y = e.Y;
if (rdoLine.Checked){
Line line(p1, p2);
lineVector.push_back(line);
}
else if (rdoRect.Checked){
int width = abs(p2.x - p1.x);
int height = abs(p2.y - p1.y);
Rect rect(p1, width, height);
rectVector.push_back(rect);
}
//改变
else if (...){
//...
circleVector.push_back(circle);
}
//...
this->Refresh();
Form::OnMouseUp(e);
}
void MainForm::OnPaint(const PaintEventArgs& e){
//---------------------------------------------------------
//针对直线
for (int i = 0; i < lineVector.size(); i++){
e.Graphics.DrawLine(Pens.Red,
lineVector[i].start.x,
lineVector[i].start.y,
lineVector[i].end.x,
lineVector[i].end.y);
}
//针对矩形
for (int i = 0; i < rectVector.size(); i++){
e.Graphics.DrawRectangle(Pens.Red,
rectVector[i].leftUp,
rectVector[i].width,
rectVector[i].height);
}
//改变
//针对圆形
for (int i = 0; i < circleVector.size(); i++){
e.Graphics.DrawCircle(Pens.Red,
circleVector[i]);
}
//---------------------------------------------------------
//...
Form::OnPaint(e);
}
在OnPain中，画不同的图形，e.Graphics需要调用不同的画图函数，并且随着画的类型的增加，则需要不断地修改原先OnPain中的代码，利用类的多态性可以解决这个问题，用到了策略模式。
class Shape//创建一个虚基类，分别让不同的图形类继承于它，相当于提供了一个接口。
{
public:
virtual void Draw() = 0;
}
class Point{
public:
int x;
int y;
};
class Line:public Shape
{
public:
Point start;
Point end;
Line(const Point& start, const Point& end){
this->start = start;
this->end = end;
}
void Draw(const Graphics& g)
{
g.DrawLine(start,end);
}
};
class Rect:public Shape
{
private:
Point leftUp;
int width;
int height;
public:
Rect(const Point& leftUp, int width, int height){
this->leftUp = leftUp;
this->width = width;
this->height = height;
}
void Draw(const Graphics& g)
{
g.DrawRectangle(leftUp,width,height);
}
};
//增加
class Circle
{
private:
Point center;
int radius;
public:
Circle(const &_center, int _radius)
{
this->center = _center;
this->radius = radius;
}
void Draw(const Graphics &g)
{
g.DrawCircle(center,radius);
}
};
class MainForm : public Form {
private:
Point p1;
Point p2;
vector<Shape*> shapeVector;
public:
MainForm(){
//...
}
protected:
virtual void OnMouseDown(const MouseEventArgs& e);
virtual void OnMouseUp(const MouseEventArgs& e);
virtual void OnPaint(const PaintEventArgs& e);
};
void MainForm::OnMouseDown(const MouseEventArgs& e){
p1.x = e.X;
p1.y = e.Y;
//...
Form::OnMouseDown(e);
}
void MainForm::OnMouseUp(const MouseEventArgs& e){
p2.x = e.X;
p2.y = e.Y;
if (rdoLine.Checked){
Line *line = new line(p1, p2);
shapeVector->push_back(line);
}
else if (rdoRect.Checked){
int width = abs(p2.x - p1.x);
int height = abs(p2.y - p1.y);
Rect *rect = new Rect(p1, width, height);
shapeVector->push_back(rect);
}
//改变
else if (...){
//...
shapeVector->push_back(circle);
}
//...
this->Refresh();
Form::OnMouseUp(e);
}
void MainForm::OnPaint(const PaintEventArgs& e){
//针对直线
for (int i = 0; i < shapeVector.size(); i++){
shapeVector[i]->Draw(e.Graphics);
}
//...
Form::OnPaint(e);
}
可以看到，OnPaint函数简洁了很多，而且图形的类型增加，也不会影响这里的代码。
