QDropEvent

[addu]

Wysota

i have gone through the below link

http://www.qtsoftware.com/developer/...-23.4700087965..

same thing only i followed ...please i request you provide me one sample example


Thanks

Addu R

[wysota]

Learn, don't copy without thinking.

[addu]

I am trying to execute sample example.. while executing i am getting following errors

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QtGui/QMainWindow>
#include <QTreeWidgetItem>
#include <QMimeData>
 
namespace Ui
{
    class MainWindowClass;
}
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();
     bool dropMimeData(QTreeWidgetItem *parent, int index, const QMimeData *data, Qt::DropAction action);
     QMimeData *mimeData(const QList<QTreeWidgetItem *> items) const;
private:
    Ui::MainWindowClass *ui;
protected:
       void dragEnterEvent(QDragEnterEvent e);
        void dragMoveEvent(QDragMoveEvent e) ;
 
 
};
 
#endif // MAINWINDOW_H

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QtGui/QMainWindow>
#include <QTreeWidgetItem>
#include <QMimeData>

namespace Ui
{
    class MainWindowClass;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();
     bool dropMimeData(QTreeWidgetItem *parent, int index, const QMimeData *data, Qt::DropAction action);
     QMimeData *mimeData(const QList<QTreeWidgetItem *> items) const;
private:
    Ui::MainWindowClass *ui;
protected:
       void dragEnterEvent(QDragEnterEvent e);
        void dragMoveEvent(QDragMoveEvent e) ;


};

#endif // MAINWINDOW_H

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mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QMessageBox>
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindowClass)
{
    ui->setupUi(this);
    ui->treeWidget->setColumnCount(2);
    ui->treeWidget->setAcceptDrops( true );
        // The tree supports dragging of its own items
     ui->treeWidget->setDragEnabled(true);
      QTreeWidgetItem *itemOne = new QTreeWidgetItem(ui->treeWidget);
        QTreeWidgetItem *itemTwo = new QTreeWidgetItem(ui->treeWidget);
        QTreeWidgetItem *itemThree = new QTreeWidgetItem(ui->treeWidget);
 
        itemOne->setText(0, "John");
        itemTwo->setText(0, "Peter");
        itemThree->setText(0, "Kumar");
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
QMimeData *MainWindow::mimeData(const QList<QTreeWidgetItem *> items) const
{
        // Create a QByteArray to store the data for the drag.
        QByteArray text;
        // Create a data stream that operates on the binary data
        QDataStream ds(&text, QIODevice::WriteOnly);
        // Add each item's text for col 0 to the stream
        for (int i=0;i<items.size();i++)
               ds << items.at(i)->text(0);
        QMimeData *md = new QMimeData;
        // Set the data associated with the mime type foo/bar to ba
        md->setData("foo/bar", text);
        return md;
}
bool MainWindow::dropMimeData(QTreeWidgetItem *parent, int index, const
                                             QMimeData *data, Qt::DropAction action)
{
        if (parent) {
               // Create a QByteArray from the mimedata associated with foo/bar
               QByteArray text = data->data("foo/bar");
               // Create a data stream that operates on the binary data
               QDataStream ds(&text, QIODevice::ReadOnly);
               while (!ds.atEnd()) {
                      QString str;
                      // Read a byte from the stream into the string
                      ds >> str;
                      // Create a new item that has the item that is dropped on as a parent
 
                      QTreeWidgetItem *newItem = new QTreeWidgetItem(parent);
                      newItem->setText(0, str);
               }
        }
        return true;
}
void MainWindow::dragEnterEvent(QDragEnterEvent event)
{
    event.accept();
}
 
 
  void MainWindow::dragMoveEvent(QDragMoveEvent event)
  {
   event.accept();
  }

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QMessageBox>
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindowClass)
{
    ui->setupUi(this);
    ui->treeWidget->setColumnCount(2);
    ui->treeWidget->setAcceptDrops( true );
        // The tree supports dragging of its own items
     ui->treeWidget->setDragEnabled(true);
      QTreeWidgetItem *itemOne = new QTreeWidgetItem(ui->treeWidget);
        QTreeWidgetItem *itemTwo = new QTreeWidgetItem(ui->treeWidget);
        QTreeWidgetItem *itemThree = new QTreeWidgetItem(ui->treeWidget);

        itemOne->setText(0, "John");
        itemTwo->setText(0, "Peter");
        itemThree->setText(0, "Kumar");
}

MainWindow::~MainWindow()
{
    delete ui;
}
QMimeData *MainWindow::mimeData(const QList<QTreeWidgetItem *> items) const
{
        // Create a QByteArray to store the data for the drag.
        QByteArray text;
        // Create a data stream that operates on the binary data
        QDataStream ds(&text, QIODevice::WriteOnly);
        // Add each item's text for col 0 to the stream
        for (int i=0;i<items.size();i++)
               ds << items.at(i)->text(0);
        QMimeData *md = new QMimeData;
        // Set the data associated with the mime type foo/bar to ba
        md->setData("foo/bar", text);
        return md;
}
bool MainWindow::dropMimeData(QTreeWidgetItem *parent, int index, const
                                             QMimeData *data, Qt::DropAction action)
{
        if (parent) {
               // Create a QByteArray from the mimedata associated with foo/bar
               QByteArray text = data->data("foo/bar");
               // Create a data stream that operates on the binary data
               QDataStream ds(&text, QIODevice::ReadOnly);
               while (!ds.atEnd()) {
                      QString str;
                      // Read a byte from the stream into the string
                      ds >> str;
                      // Create a new item that has the item that is dropped on as a parent

                      QTreeWidgetItem *newItem = new QTreeWidgetItem(parent);
                      newItem->setText(0, str);
               }
        }
        return true;
}
void MainWindow::dragEnterEvent(QDragEnterEvent event)
{
    event.accept();
}


  void MainWindow::dragMoveEvent(QDragMoveEvent event)
  {
   event.accept();
  }

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errors:
error: `event' has incomplete type
error: forward declaration of `struct QDragEnterEvent'
error: invalid use of undefined type `struct QDragEnterEvent'
error: forward declaration of `struct QDragEnterEvent'
error: `event' has incomplete type

[wysota]

You didn't include proper files so the compiler complains about it.

[addu]

Hi wysota

In above example .. when running the application mimedata, Dropmimedata is never invoked..

I put the QmessageBox and qDebug() statement there.. But i didn't get any responce from that functions..


Thanks

Yuvaraj R

[wysota]

It will never be invoked because you're overriding the whole drag&drop mechanism present in Item Views. And you still didn't bother to read the docs...

[addu]

Hi wysota..

I have been reading the doc and right now i am referring the item/view based Puzzle example...

whenever make drag the data are stored at time mime data function will be called ..

whenver we dropping the item that time dropmime data function will be called..

if i don't override drag and drop functions also that two functions are not invoking...



Thanks

Addu R

[wysota]

You only need to override mimeData() and dropMimeData(), nothing more.

[addu]

Dear Wysota

I over ride the drag and drop function by setting the QTreeWidget class as a parent..

sample code

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QTreeWidgetItem>
#include <QtGui/QMainWindow>
#include <QDropEvent>
namespace Ui
{
    class MainWindowClass;
}
 
class MainWindow : public QMainWindow,public QTreeWidget
{
    Q_OBJECT
 
public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();
       bool dropMimeData(QTreeWidgetItem *parent, int index, const QMimeData *data, Qt::DropAction action);
     QMimeData *mimeData(const QList<QTreeWidgetItem *> items) const;
     void dragEnterEvent(QDragEnterEvent *e);
     void dragMoveEvent(QDragMoveEvent *e) ;
private:
    Ui::MainWindowClass *ui;
 
};
 
#endif // MAINWINDOW_H

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QTreeWidgetItem>
#include <QtGui/QMainWindow>
#include <QDropEvent>
namespace Ui
{
    class MainWindowClass;
}

class MainWindow : public QMainWindow,public QTreeWidget
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();
       bool dropMimeData(QTreeWidgetItem *parent, int index, const QMimeData *data, Qt::DropAction action);
     QMimeData *mimeData(const QList<QTreeWidgetItem *> items) const;
     void dragEnterEvent(QDragEnterEvent *e);
     void dragMoveEvent(QDragMoveEvent *e) ;
private:
    Ui::MainWindowClass *ui;

};

#endif // MAINWINDOW_H

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mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QMessageBox>
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent),QTreeWidget(parent), ui(new Ui::MainWindowClass)
{
    ui->setupUi(this);
    ui->treeWidget->setColumnCount(1);
    ui->treeWidget->setAcceptDrops( true );
    // The tree supports dragging of its own items
    ui->treeWidget->setDragEnabled(true);
    QTreeWidgetItem *itemOne = new QTreeWidgetItem(ui->treeWidget);
    QTreeWidgetItem *itemTwo = new QTreeWidgetItem(ui->treeWidget);
    QTreeWidgetItem *itemThree = new QTreeWidgetItem(ui->treeWidget);
    itemOne->setText(0, "John");
    itemTwo->setText(0, "Peter");
    itemThree->setText(0, "Kumar");
}
QMimeData *MainWindow::mimeData(const QList<QTreeWidgetItem *> items) const
{
    QMessageBox::information(0,"",QString("Drag and Drop"));
    // Create a QByteArray to store the data for the drag.
    QByteArray text;
    // Create a data stream that operates on the binary data
    QDataStream ds(&text, QIODevice::WriteOnly);
    // Add each item's text for col 0 to the stream
    for (int i=0;i<items.size();i++)
        ds << items.at(i)->text(0);
    QMimeData *md = new QMimeData;
    // Set the data associated with the mime type foo/bar to ba
    md->setData("foo/bar", text);
    return md;
}
bool MainWindow::dropMimeData(QTreeWidgetItem *parent, int index, const
                              QMimeData *data, Qt::DropAction action)
{
 
    if (parent) {
        // Create a QByteArray from the mimedata associated with foo/bar
        QByteArray text = data->data("foo/bar");
        // Create a data stream that operates on the binary data
        QDataStream ds(&text, QIODevice::ReadOnly);
        while (!ds.atEnd()) {
            QString str;
            // Read a byte from the stream into the string
            ds >> str;
            // Create a new item that has the item that is dropped on as a parent
 
            QTreeWidgetItem *newItem = new QTreeWidgetItem(parent);
            newItem->setText(0, str);
        }
    }
    return true;
}
void MainWindow::dragEnterEvent(QDragEnterEvent *e)
{
    e->accept();
}
 
 
  void MainWindow::dragMoveEvent(QDragMoveEvent *e)
  {
    e->accept();
  }
 
MainWindow::~MainWindow()
{
    delete ui;
}

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QMessageBox>
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent),QTreeWidget(parent), ui(new Ui::MainWindowClass)
{
    ui->setupUi(this);
    ui->treeWidget->setColumnCount(1);
    ui->treeWidget->setAcceptDrops( true );
    // The tree supports dragging of its own items
    ui->treeWidget->setDragEnabled(true);
    QTreeWidgetItem *itemOne = new QTreeWidgetItem(ui->treeWidget);
    QTreeWidgetItem *itemTwo = new QTreeWidgetItem(ui->treeWidget);
    QTreeWidgetItem *itemThree = new QTreeWidgetItem(ui->treeWidget);
    itemOne->setText(0, "John");
    itemTwo->setText(0, "Peter");
    itemThree->setText(0, "Kumar");
}
QMimeData *MainWindow::mimeData(const QList<QTreeWidgetItem *> items) const
{
    QMessageBox::information(0,"",QString("Drag and Drop"));
    // Create a QByteArray to store the data for the drag.
    QByteArray text;
    // Create a data stream that operates on the binary data
    QDataStream ds(&text, QIODevice::WriteOnly);
    // Add each item's text for col 0 to the stream
    for (int i=0;i<items.size();i++)
        ds << items.at(i)->text(0);
    QMimeData *md = new QMimeData;
    // Set the data associated with the mime type foo/bar to ba
    md->setData("foo/bar", text);
    return md;
}
bool MainWindow::dropMimeData(QTreeWidgetItem *parent, int index, const
                              QMimeData *data, Qt::DropAction action)
{

    if (parent) {
        // Create a QByteArray from the mimedata associated with foo/bar
        QByteArray text = data->data("foo/bar");
        // Create a data stream that operates on the binary data
        QDataStream ds(&text, QIODevice::ReadOnly);
        while (!ds.atEnd()) {
            QString str;
            // Read a byte from the stream into the string
            ds >> str;
            // Create a new item that has the item that is dropped on as a parent

            QTreeWidgetItem *newItem = new QTreeWidgetItem(parent);
            newItem->setText(0, str);
        }
    }
    return true;
}
void MainWindow::dragEnterEvent(QDragEnterEvent *e)
{
    e->accept();
}


  void MainWindow::dragMoveEvent(QDragMoveEvent *e)
  {
    e->accept();
  }

MainWindow::~MainWindow()
{
    delete ui;
}

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I have one doubt .,Mainwindow class having two sub classes.which sub class drag enter & drag move functions it will take..

please clear me

Thanks

Addu R

[nish]

hey man.. u cannot inherit from both QMainWindow and QTreeWidget. make seperate classes for both of them.. ..
tomoro if i get the Fkin time i will read your posts and problems..

[wysota]

class MainWindow : public QMainWindow,public QTreeWidget

class MainWindow : public QMainWindow,public QTreeWidget

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Ah man.... did you even try to compile this code?

At moments like this I'm beginning to think if we're even remotely close to managing to educate people here...

Maybe we should get some programming certification scheme here or something...

[nish]

what i found is many ppl know c++ but do not know one of these concepts 1. inheritance 2. virtual 3. pointers. And they jump into Qt. This where all starts to mess up.

[wysota]

what i found is many ppl know c++ but do not know one of these concepts 1. inheritance 2. virtual 3. pointers.

It's like "they know how to drive but only on the first gear and only straight ahead". It's hard to call it "knowing how to drive" then... But that you don't know how to program is not a big deal. It starts to be a deal when you're not learning and still continue to bang your head against the wall.

[faldzip]

...but do not know one of these concepts...

and sometimes not only one :P