Qt：開啓拖動項

頭文件：

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

mylistwidget.h（基類繼承QListWidget 類型選擇QWidget）

#ifndef MYLISTWIDGET_H
#define MYLISTWIDGET_H

#include <QListWidget>
#include <QApplication>
#include <QtGui>

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

signals:

public slots:

private:
    void mousePressEvent(QMouseEvent *event);
    void mouseMoveEvent(QMouseEvent *event);
private:
    QPoint m_dragpoint;
    QListWidgetItem *m_dragItem;
};

#endif // MYLISTWIDGET_H

源文件：

main.cpp

#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    ui->listWidget->addItem("Bunfly");
    ui->listWidget->addItem("SuperMan");
    ui->listWidget->addItem("Apple");
}

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

mylistwidget.cpp

#include "mylistwidget.h"

MyListWidget::MyListWidget(QWidget *parent) :
    QListWidget(parent)
{
}

void MyListWidget::mousePressEvent(QMouseEvent *event)
{
    m_dragpoint = event->pos(); //記錄按下鼠標時的起始位
    m_dragItem = this->itemAt(event->pos());   //記錄拖動項

    QListWidget::mousePressEvent(event);      //調用父類函數保持原有的按鍵行爲
}

void MyListWidget::mouseMoveEvent(QMouseEvent *event)
{
    if(!(event->buttons() & Qt::LeftButton))
    {
        return;
    }
    //移動距離太近
    if((event->pos() - m_dragpoint).manhattanLength()
            < QApplication::startDragDistance())
    {
        return;
    }
    //沒選中項
    if(!m_dragItem)
    {
        return;
    }
    //建立拖動項
    QString txt = m_dragItem->text();
    QDrag *drag = new QDrag(this);

    QMimeData *mimedata = new QMimeData;

    mimedata->setText(txt);
    drag->setMimeData(mimedata);

    //拖動時的圖像顯示
    QPixmap drag_img(120,18);
    QPainter painter(&drag_img);

    painter.drawText(QRectF(0,0,120,18),txt,QTextOption(Qt::AlignVCenter));
    drag->setPixmap(drag_img);

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

    if(Qt::IgnoreAction != resulte) //檢查操作是否成功
    {
        //按住ctrl拖動：CopyAction;
        //否則：MoveAction
    }
    else
    {

    }
}

設計界面：（提升的自定義控件）

效果展示：