下面代码为什么不能画出方形？谢谢

[snowedforest]

void CPicTestDlg::OnButton2()
{
CDC*pdc=this->GetDC();
CDC*dc2=new CDC;
dc2->CreateCompatibleDC(pdc);
dc2->Rectangle(1,1,100,100);
pdc->StretchBlt(0,0,40,35,dc2,0,0,40,35,SRCCOPY );
pdc->DeleteDC();
dc2->DeleteDC();
delete dc2;

}

[zhuzhufox]

没有兼容位图。

[lanstar200]

pdc->DeleteDC();//改成ReleaseDC(pdc);

[快乐鹦鹉]

必须给兼容DC选入一副位图。就是先Create一个Bitmap

[hdqqq]

按照你的代码，要显示图像，需要不停地按 button2。

画图不是在这里的。

[lanstar200]

CDC*pdc=this->GetDC();
CDC*dc2=new CDC;
dc2->CreateCompatibleDC(pdc);
CBitmap bmp;
bmp.CreateCompatibleBitmap(pdc , 400 , 300);
CBitmap *oldbm = dc2->SelectObject(&bmp);
dc2->Rectangle(1,1,100,100);
pdc->StretchBlt(0,0,40,35,dc2,0,0,40,35,SRCCOPY );
dc2->SelectObject(oldbm);
bmp.DeleteObject();
ReleaseDC(pdc);
dc2->DeleteDC();
delete dc2;

[zhuzhufox]

CDC*pdc=this->GetDC();
CDC*dc2=new CDC;
CBitmap bmp,*pOldBitmap;
bmp.CreateCompatibleBitmap(pdc,200,200);
dc2->CreateCompatibleDC(pdc);
pOldBitmap = dc2->SelectObject(&bmp);
dc2->BitBlt(0,0,200,200,NULL,0,0,WHITENESS);
dc2->Rectangle(1,1,100,100);
pdc->StretchBlt(0,0,40,35,dc2,0,0,40,35,SRCCOPY );

dc2->SelectObject(pOldBitmap);
pdc->DeleteDC();
dc2->DeleteDC();
delete dc2;
Invalidate(FALSE);

[zhuzhufox]

Invalidate(FALSE);
也记得要加上