Drag and drop in QML [closed]

问题

How can I develop drag and drop functionality in QML? I want to drag and drop one image to another.

回答1:

At this point in time, you will probably need to use C++, especially if you want to accept drops from outside the QML application (e.g. the user drags a file from a file manager to your app). Here's an example component class to implement a DropArea item:

DropArea.h:

#ifndef DropArea_H
#define DropArea_H

#include <QDeclarativeItem>

/**
    An oversimplified prototype Item which accepts any drop that includes
    data with mime type of text/plain, and just emits the text.
*/
class DropArea : public QDeclarativeItem
{
    Q_OBJECT
    Q_PROPERTY(bool acceptingDrops READ isAcceptingDrops WRITE setAcceptingDrops NOTIFY acceptingDropsChanged)

public:
    DropArea(QDeclarativeItem *parent=0);
    bool isAcceptingDrops() const { return m_accepting; }
    void setAcceptingDrops(bool accepting);

signals:
    void textDrop(QString text);
    void acceptingDropsChanged();

protected:
    void dragEnterEvent(QGraphicsSceneDragDropEvent *event);
    void dragLeaveEvent(QGraphicsSceneDragDropEvent *event);
    void dropEvent(QGraphicsSceneDragDropEvent *event);

private:
    bool m_accepting;
};

#endif

DropArea.cpp:

#include <QGraphicsSceneDragDropEvent>
#include <QMimeData>
#include "DropArea.h"

DropArea::DropArea(QDeclarativeItem *parent)
        : QDeclarativeItem(parent),
    m_accepting(true)
{
    setAcceptDrops(m_accepting);
}

void DropArea::dragEnterEvent(QGraphicsSceneDragDropEvent *event)
{
    event->acceptProposedAction();
    setCursor(Qt::DragMoveCursor);
}

void DropArea::dragLeaveEvent(QGraphicsSceneDragDropEvent *event)
{
    unsetCursor();
}

void DropArea::dropEvent(QGraphicsSceneDragDropEvent *event)
{
    emit textDrop(event->mimeData()->text());
    unsetCursor();
}

void DropArea::setAcceptingDrops(bool accepting)
{
    if (accepting == m_accepting)
                return;

    m_accepting = accepting;
    setAcceptDrops(m_accepting);
    emit acceptingDropsChanged();
}

your QML:

DropArea {
    onTextDrop: ...
}

And you can implement a DragSourceArea similarly.

回答2:

I know it's been a while but I struggled so much with this I wanted to share the Qt5 version:

Based on ecloud an Michael's example:

DropArea.h:

#ifndef DropArea_H
#define DropArea_H

#include <QQuickItem>

/**
    An oversimplified prototype Item which accepts any drop that includes
    data with mime type of text/plain, and just emits the text.
*/
class DropArea : public QQuickItem
{
    Q_OBJECT
    Q_PROPERTY(bool acceptingDrops READ isAcceptingDrops WRITE setAcceptingDrops NOTIFY acceptingDropsChanged)

public:
    DropArea(QQuickItem *parent=0);
    bool isAcceptingDrops() const { return m_accepting; }
    void setAcceptingDrops(bool accepting);

signals:
    void textDrop(QString text);
    void acceptingDropsChanged();

protected:
    void dragEnterEvent(QDragEnterEvent *event);
    void dragLeaveEvent(QDragLeaveEvent *event);
    void dropEvent(QDropEvent *event);

private:
    bool m_accepting;
};

#endif

DropArea.cpp:

#include <QGraphicsSceneDragDropEvent>
#include <QMimeData>
#include "DropArea.h"

DropArea::DropArea(QQuickItem *parent)
        : QQuickItem (parent),
    m_accepting(true)
{
    setFlag(QQuickItem::ItemAcceptsDrops, m_accepting);
}

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

void DropArea::dragLeaveEvent(QDragLeaveEvent *event)
{
    unsetCursor();
}

void DropArea::dropEvent(QDropEvent *event)
{
    qDebug() << event->mimeData()->text();
    unsetCursor();
}

void DropArea::setAcceptingDrops(bool accepting)
{
    if (accepting == m_accepting)
                return;

    m_accepting = accepting;
    setFlag(QQuickItem::ItemAcceptsDrops, m_accepting);
    emit acceptingDropsChanged();
}

Qml:

Drop2 {
  id: myDropArea    
}

回答3:

QML: drag, drop and resize dynamic element, one simple example found in one KDE blog, The example is completely written in QML

http://kdeblog.mageprojects.com/2012/08/16/qml-drag-drop-and-resize-dynamic-element-followup/

来源：https://stackoverflow.com/questions/7618307/drag-and-drop-in-qml

标签

qml