以下Qt程序显示出来的结果为何坐标是负值？ [复制链接]

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离线ceiwei

新手上路

只看楼主倒序阅读楼主发表于: 2017-02-06

关键代码是：
    painter.drawText(20,1*50,tr("%1").arg((1*50)));

    painter.drawText(20,2*50,tr("%1").arg((2*50)))
按道理i增加了，应该是在更高的位置显示出来，而这里的位置更低;所有代码是：

#include "pieview.h"
#include <QPainter>

PieView::PieView(QWidget *parent) :
    QAbstractItemView(parent)
{
}

void PieView::paintEvent(QPaintEvent *)
{
    QPainter painter(viewport());
    painter.setPen(Qt::black);
    int x0=40;
    int y0=250;
    //y坐标轴
    painter.drawLine(x0,y0,40,30);
    painter.drawLine(38,32,40,30);
    painter.drawLine(40,30,42,32);
    painter.drawText(20,30,tr("销售数量"));
    painter.drawText(20,1*50,tr("%1").arg((1*50)));
    painter.drawText(20,2*50,tr("%1").arg((2*50)));

    //x 坐标轴
    painter.drawLine(x0,y0,540,250);
    painter.drawLine(538,248,540,250);
    painter.drawLine(540,250,538,252);
    painter.drawText(545,250,tr("品牌"));

    int pos=x0+20;
    int row;
    for(row=0;row<model()->rowCount(rootIndex());row++)
    {
        QModelIndex index=model()->index(row,0,rootIndex());
        QString dep=model()->data(index).toString();

        painter.drawText(pos,y0+20,dep);
        pos+=50;
    }
    int posN=x0+20;
    for(row=0;row<model()->rowCount(rootIndex());row++)
    {
        QModelIndex index=model()->index(row,1,rootIndex());
        int sell=model()->data(index).toDouble();

        int width=10;
        QModelIndex colorIndex = model()->index(row,0,rootIndex());
        QColor color = QColor(model()->data(colorIndex,Qt::DecorationRole).toString());
        if(selections->isSelected(index))
            painter.setBrush(QBrush(color,Qt::Dense3Pattern));
        else
            painter.setBrush(QBrush(color));

        painter.drawRect(QRect(posN,y0-sell*10,width,sell*10));
        QRegion regionM(posN,y0-sell*10,width,sell*10);
        RegionList<<regionM;

        posN+=50;
    }
}

void PieView::setSelectionModel(QItemSelectionModel *selectionModel)
{
    selections = selectionModel;
}

QRegion PieView::itemRegion(QModelIndex index)
{
    QRegion region;
    if (index.column() == 1)        // 销售数量
        region = RegionList[index.row()];
    return region;
}

QModelIndex PieView::indexAt(const QPoint &point) const
{
    QPoint newPoint(point.x(),point.y());
    QRegion region;
    foreach(region,RegionList)                // 销售数量列
    {
        if (region.contains(newPoint))
        {
            int row = RegionList.indexOf(region);
            QModelIndex index = model()->index(row,1,rootIndex());
            return index;
        }
    }
    return QModelIndex();
}

QRect PieView::visualRect(const QModelIndex &index) const{}
void PieView::scrollTo(const QModelIndex &index, ScrollHint hint){}
QModelIndex PieView::moveCursor(CursorAction cursorAction, Qt::KeyboardModifiers modifiers){}
int PieView::horizontalOffset()const{}
int PieView::verticalOffset()const{}
bool PieView::isIndexHidden(const QModelIndex &index) const{}
void PieView::setSelection(const QRect &rect, QItemSelectionModel::SelectionFlags command){}
QRegion PieView::visualRegionForSelection(const QItemSelection &selection) const{}

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离线firebolt

侠客

只看该作者 1楼发表于: 2017-02-06

坐标原点在窗口的左上角，x向右增长，y向下增长。你需要调整一下算法。

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以下Qt程序显示出来的结果为何坐标是负值？ [复制链接]