Drag and drop : Drag Drop « Qt « C++






Drag and drop

  
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#ifndef DRAGWIDGET_H
#define DRAGWIDGET_H

#include <QByteArray>
#include <QFrame>
#include <QString>
#include <QStringList>

class QComboBox;
class QFrame;
class QLabel;
class QTextBrowser;

class DragWidget : public QFrame
{
    Q_OBJECT

public:
    DragWidget(QWidget *parent);
    void setData(const QString &mimetype, const QByteArray &newData);

signals:
    void dragResult(const QString &actionText);
    void mimeTypes(const QStringList &types);

protected:
    void dragEnterEvent(QDragEnterEvent *event);
    void dropEvent(QDropEvent *event);
    void mouseMoveEvent(QMouseEvent *event);
    void mousePressEvent(QMouseEvent *event);

private:
    QByteArray data;
    QLabel *dragDropLabel;
    QPoint dragStartPosition;
    QString mimeType;
};

#endif








#include <QtGui>

#include "dragwidget.h"

DragWidget::DragWidget(QWidget *parent)
    : QFrame(parent)
{
    setFrameStyle(QFrame::StyledPanel | QFrame::Sunken);
    dragDropLabel = new QLabel("", this);
    dragDropLabel->setAlignment(Qt::AlignHCenter);

    QHBoxLayout *layout = new QHBoxLayout(this);
    layout->addStretch(0);
    layout->addWidget(dragDropLabel);
    layout->addStretch(0);

    setAcceptDrops(true);
}

// Accept all actions, but deal with them separately later.

void DragWidget::dragEnterEvent(QDragEnterEvent *event)
{
    event->acceptProposedAction();
}



void DragWidget::dropEvent(QDropEvent *event)
{
    if (event->source() == this && event->possibleActions() & Qt::MoveAction)
        return;



    if (event->proposedAction() == Qt::MoveAction) {
        event->acceptProposedAction();
        // Process the data from the event.

        emit dragResult(tr("The data was moved here."));

    } else if (event->proposedAction() == Qt::CopyAction) {
        event->acceptProposedAction();
        // Process the data from the event.

        emit dragResult(tr("The data was copied here."));

    } else {
        // Ignore the drop.
        return;
    }

    // End of quote

    emit mimeTypes(event->mimeData()->formats());
    setData(event->mimeData()->formats()[0],
            event->mimeData()->data(event->mimeData()->formats()[0]));

}



void DragWidget::mousePressEvent(QMouseEvent *event)
{
    if (event->button() == Qt::LeftButton)
        dragStartPosition = event->pos();
}



void DragWidget::mouseMoveEvent(QMouseEvent *event)
{
    if (!(event->buttons() & Qt::LeftButton))
        return;
    if ((event->pos() - dragStartPosition).manhattanLength()
         < QApplication::startDragDistance())
        return;

    QDrag *drag = new QDrag(this);
    QMimeData *mimeData = new QMimeData;

    mimeData->setData(mimeType, data);
    drag->setMimeData(mimeData);

    Qt::DropAction dropAction = drag->exec(Qt::CopyAction | Qt::MoveAction);


    switch (dropAction) {
        case Qt::CopyAction:
            emit dragResult(tr("The text was copied."));
            break;
        case Qt::MoveAction:
            emit dragResult(tr("The text was moved."));
            break;
        default:
            emit dragResult(tr("Unknown action."));
            break;
    }

}


void DragWidget::setData(const QString &mimetype, const QByteArray &newData)
{
    mimeType = mimetype;
    data = QByteArray(newData);

    dragDropLabel->setText(tr("%1 bytes").arg(data.size()));

    QStringList formats;
    formats << mimetype;
    emit mimeTypes(formats);
}











#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QPixmap>
#include <QPoint>

class QComboBox;
class QLabel;
class QLineEdit;
class QMouseEvent;
class QTextEdit;
class DragWidget;

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);

public slots:
    void setDragResult(const QString &actionText);
    void setMimeTypes(const QStringList &types);

private:
    QComboBox *mimeTypeCombo;
    DragWidget *dragWidget;
};

#endif






#include <QtGui>

#include "dragwidget.h"
#include "mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    QFrame *centralWidget = new QFrame(this);

    QLabel *mimeTypeLabel = new QLabel(tr("MIME types:"), centralWidget);
    mimeTypeCombo = new QComboBox(centralWidget);

    QLabel *dataLabel = new QLabel(tr("Amount of data (bytes):"), centralWidget);
    dragWidget = new DragWidget(centralWidget);

    connect(dragWidget, SIGNAL(mimeTypes(const QStringList &)),
            this, SLOT(setMimeTypes(const QStringList &)));
    connect(dragWidget, SIGNAL(dragResult(const QString &)),
            this, SLOT(setDragResult(const QString &)));

    QVBoxLayout *mainLayout = new QVBoxLayout(centralWidget);
    mainLayout->addWidget(mimeTypeLabel);
    mainLayout->addWidget(mimeTypeCombo);
    mainLayout->addSpacing(32);
    mainLayout->addWidget(dataLabel);
    mainLayout->addWidget(dragWidget);

    statusBar();
    dragWidget->setData(QString("text/plain"), QByteArray("Hello world"));
    setCentralWidget(centralWidget);
    setWindowTitle(tr("Drag and Drop"));
}

void MainWindow::setDragResult(const QString &actionText)
{
    statusBar()->showMessage(actionText);
}

void MainWindow::setMimeTypes(const QStringList &types)
{
    mimeTypeCombo->clear();
    mimeTypeCombo->addItems(types);
}





#include <QtGui>

#include "mainwindow.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MainWindow *window1 = new MainWindow;
    MainWindow *window2 = new MainWindow;
    window1->show();
    window2->show();
    return app.exec();
}

   
    
  








Related examples in the same category

1.Drag and drop text
2.Drop action
3.Drop event
4.Drop rectangle
5.Drag Drop List Model
6.Port for drop event