拖曳QTextEdit QListWidget

#ifndef TEXTEDIT_H
#define TEXTEDIT_H

#include <QTextEdit>

class TextEdit : public QTextEdit
{
    Q_OBJECT
public:
    explicit TextEdit(QWidget *parent = 0);

protected:
    void dragEnterEvent(QDragEnterEvent *);
    void dropEvent(QDropEvent *);

private:
    bool readFile(const QString &filename);
};

#endif // TEXTEDIT_H

#include "textedit.h"
#include <QtWidgets>

TextEdit::TextEdit(QWidget *parent) :
    QTextEdit(parent)
{
}

void TextEdit::dragEnterEvent(QDragEnterEvent *event)
{
    if (event->mimeData()->hasFormat("text/uri-list")) {
        event->acceptProposedAction();
    }
}

void TextEdit::dropEvent(QDropEvent *event)
{
    QList<QUrl> urls = event->mimeData()->urls();
    if (urls.isEmpty()) {
        qDebug() << "dropEvent urls";
        return;
    }

    QString filename = urls.first().toLocalFile();
    if (filename.isEmpty()) {
        qDebug() << "dropEvent filename:" << filename;
        return;
    }

    readFile(filename);
}

bool TextEdit::readFile(const QString &filename)
{
    QFile file(filename);
    if (file.open(QFile::ReadOnly)) {
        QTextStream stream(&file);
        this->setText(stream.readAll());
        return true;
    }
    return false;
}

#ifndef LISTWIDGET_H
#define LISTWIDGET_H

#include <QListWidget>

class ListWidget : public QListWidget
{
    Q_OBJECT
public:
    explicit ListWidget(QWidget *parent = 0);

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


private:
    void performDrag();
    QPoint startPos_;
};

#endif // LISTWIDGET_H

#include "listwidget.h"
#include <QtWidgets>

ListWidget::ListWidget(QWidget *parent) :
    QListWidget(parent)
{
    this->setAcceptDrops(true);
}

void ListWidget::mousePressEvent(QMouseEvent *event)
{
    if (event->button() == Qt::LeftButton) {
        startPos_ = event->pos();
    }
    QListWidget::mousePressEvent(event);
}

void ListWidget::mouseMoveEvent(QMouseEvent *event)
{
    if (event->buttons() & Qt::LeftButton) {
        int distance = (event->pos() - startPos_).manhattanLength();
        if (distance >= QApplication::startDragDistance()) {
            performDrag();
        }
    }
    QListWidget::mouseMoveEvent(event);
}

void ListWidget::dragEnterEvent(QDragEnterEvent *event)
{
    ListWidget *source = qobject_cast<ListWidget*>(event->source());
    if (source && source != this) {
        event->setDropAction(Qt::MoveAction);
        event->accept();
    }
}

void ListWidget::dragMoveEvent(QDragMoveEvent *event)
{
    ListWidget *source = qobject_cast<ListWidget*>(event->source());
    if (source && source != this) {
        event->setDropAction(Qt::MoveAction);
        event->accept();
    }
}

void ListWidget::dropEvent(QDropEvent *event)
{
    ListWidget *source = qobject_cast<ListWidget*>(event->source());
    if (source && source != this) {
        this->addItem(event->mimeData()->text());
        event->setDropAction(Qt::MoveAction);
        event->accept();
    }
}

void ListWidget::performDrag()
{
    QListWidgetItem *item = this->currentItem();
    if (item) {
        QMimeData *mimeData = new QMimeData;
        mimeData->setText(item->text());

        QDrag *drag = new QDrag(this);
        drag->setMimeData(mimeData);
        if (drag->exec(Qt::MoveAction) == Qt::MoveAction) {
            delete item;
        }
    }
}