Question

我是Qt Creator和编码的新手，我正在尝试创建一个应用程序，其中我有一个颜色选项列表和一个区域，我可以拖动这些选项并创建一个图形项目我选择的颜色，这里是代码：

我创建了QListWidget并暂时添加了两个QListWidgetItem itens：

OptionList::OptionList(QWidget *parent) : QListWidget(parent)
{
this->setDragEnabled(true);
this->setDropIndicatorShown(true);
this->setSelectionMode(QAbstractItemView::SingleSelection);
this->setDefaultDropAction(Qt::CopyAction);
this->setViewMode(QListView::ListMode);

QListWidgetItem *blue = new QListWidgetItem;
blue->setText("Blue");
blue->setFlags(Qt::ItemIsEnabled | Qt::ItemIsSelectable | 
Qt::ItemIsDragEnabled);
addItem(blue);

QListWidgetItem *red = new QListWidgetItem;
red->setText("Red");
red->setFlags(Qt::ItemIsEnabled | Qt::ItemIsSelectable | 
Qt::ItemIsDragEnabled);
addItem(red);
}

我创建了一个QgraphicsPathItem，它接收一个字符串，具体取决于字符串，它会改变颜色

Block::Block(QString color, QGraphicsItem *parent) : QGraphicsPathItem(parent)
{
QPainterPath p;
p.addRoundedRect(0, 0, 150, 50, 2, 2);
setPath(p);
setPen(QPen(Qt::black));
if (color == "Blue")
{
    setBrush(Qt::blue);
}
else if (color == "Red")
{
    setBrush(Qt::red);
}
setFlag(QGraphicsItem::ItemIsMovable);
setFlag(QGraphicsItem::ItemIsSelectable);
}

然后，我创建了从MyScene派生的QGraphicsScene类，并重新实现了dragEnterEvent，dragMoveEvent和dropEvent

#include "myscene.h"

MyScene::MyScene()
{
setBackgroundBrush(Qt::lightGray);
}

void MyScene::dragEnterEvent(QGraphicsSceneDragDropEvent *event)
{
event->setAccepted(true);
}

void MyScene::dragMoveEvent(QGraphicsSceneDragDropEvent *event)
{
event->setAccepted(true);
}

void MyScene::dropEvent(QGraphicsSceneDragDropEvent *event)
{
QString color;
color = event->mimeData()->text();

Block *newBlock = new Block(color);

QPointF posView = event->scenePos();
newBlock->setPos(posView);

addItem(newBlock);
}

我尝试使用QString color; color = event->mimeData()->text();，但它没有工作

我知道它与QMimeData课程有关，但我不知道该怎么做

如何从列表中的项目中获取文本并将其传递给Block类以更改其颜色？

Answer 1

您必须对数据进行解码，因为QListWidget QAbstractItemView支持多选。

void MyScene::dragEnterEvent(QGraphicsSceneDragDropEvent *event){
    if(event->mimeData()->hasFormat("application/x-qabstractitemmodeldatalist"))
        event->setAccepted(true);
}
void MyScene::dragMoveEvent(QGraphicsSceneDragDropEvent *event){
    if(event->mimeData()->hasFormat("application/x-qabstractitemmodeldatalist"))
        event->setAccepted(true);
}
void MyScene::dropEvent(QGraphicsSceneDragDropEvent *event){

    QByteArray encoded = event->mimeData()->data("application/x-qabstractitemmodeldatalist");
    QDataStream stream(&encoded, QIODevice::ReadOnly);

    QStringList colors;

    while (!stream.atEnd())
    {
        int row, col;
        QMap<int,  QVariant> roleDataMap;
        stream >> row >> col >> roleDataMap;
        colors << roleDataMap[Qt::DisplayRole].toString();
    }
    QPointF posView = event->scenePos();
    for(const QString & color: colors){
        Block *newBlock = new Block(color);
        newBlock->setPos(posView);
        addItem(newBlock);
    }
}

Qt - 如何在QGraphicScene中拖放时从项目中获取文本？

1 个答案: