[提问]runtime erro [复制链接]

为什么我编写的程序，运行会出现runtime erro，而且这个错误有时出现，有时不会出现

运行错误，好办。
运行你的程序，逐项操作功能，看看哪个功能那里出问题，
在可能出问题的地方调试，逐行执行代码，就能找到
问题在哪里了。

我知道哪边有bug，但是有时运行不会报错，有时就报错。
出错代码如下：
void MyCanvas::addSelectedBox(PTBaseClass drawCellArray){
    //存储要添加选中的位置
    left=drawCellArray->cellPosition.left-4;
    right=drawCellArray->cellPosition.right-4;
    top=drawCellArray->cellPosition.top-4;
    bottom=drawCellArray->cellPosition.bottom-4;

    //添加选中框
    rect1=ownmain->mycanvas->addRect(drawCellArray->cellPosition.left-4,drawCellArray->cellPosition.top-4,6,6,QPen(QColor(255,255,255)),QBrush(QColor(0,128,0)));
    rect2=ownmain->mycanvas->addRect(drawCellArray->cellPosition.left-4,drawCellArray->cellPosition.bottom-4,6,6,QPen(QColor(255,255,255)),QBrush(QColor(0,128,0)));
    rect3=ownmain->mycanvas->addRect(drawCellArray->cellPosition.left-4,(drawCellArray->cellPosition.top+drawCellArray->cellPosition.bottom)/2-4,6,6,QPen(QColor(255,255,255)),QBrush(QColor(0,128,0)));

    rect4=ownmain->mycanvas->addRect((drawCellArray->cellPosition.left+drawCellArray->cellPosition.right)/2-4,drawCellArray->cellPosition.top-4,6,6,QPen(QColor(255,255,255)),QBrush(QColor(0,128,0)));
    rect5=ownmain->mycanvas->addRect((drawCellArray->cellPosition.left+drawCellArray->cellPosition.right)/2-4,drawCellArray->cellPosition.bottom-4,6,6,QPen(QColor(255,255,255)),QBrush(QColor(0,128,0)));

    rect6=ownmain->mycanvas->addRect(drawCellArray->cellPosition.right-4,drawCellArray->cellPosition.top-4,6,6,QPen(QColor(255,255,255)),QBrush(QColor(0,128,0)));
    rect7=ownmain->mycanvas->addRect(drawCellArray->cellPosition.right-4,(drawCellArray->cellPosition.top+drawCellArray->cellPosition.bottom)/2-4,6,6,QPen(QColor(255,255,255)),QBrush(QColor(0,128,0)));
    rect8=ownmain->mycanvas->addRect(drawCellArray->cellPosition.right-4,drawCellArray->cellPosition.bottom-4,6,6,QPen(QColor(255,255,255)),QBrush(QColor(0,128,0)));

    selected=true;
  }

//清除选中框
if(left!=0 && right!=0 && top!=0 && bottom!=0){
             QGraphicsItem *item1=ownmain->mycanvas->rect1;
             ownmain->mycanvas->removeItem(item1);
             QGraphicsItem *item2=ownmain->mycanvas->rect2;
             ownmain->mycanvas->removeItem(item2);
             QGraphicsItem *item3=ownmain->mycanvas->rect3;
             ownmain->mycanvas->removeItem(item3);
             QGraphicsItem *item4=ownmain->mycanvas->rect4;
             ownmain->mycanvas->removeItem(item4);
             QGraphicsItem *item5=ownmain->mycanvas->rect5;
             ownmain->mycanvas->removeItem(item5);
             QGraphicsItem *item6=ownmain->mycanvas->rect6;
             ownmain->mycanvas->removeItem(item6);
             QGraphicsItem *item7=ownmain->mycanvas->rect7;
             ownmain->mycanvas->removeItem(item7);
             QGraphicsItem *item8=ownmain->mycanvas->rect8;
             ownmain->mycanvas->removeItem(item8);

              selected=false;
              pt_selected=false;
              connect_selected=false;
          }