Qt拖放操作和打印操作的实现

    void dragEnterEvent(QDragEnterEvent *event);   //拖动进入事件
    void dropEvent(QDropEvent *event);             //放下事件

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QDragEnterEvent>
#include <QUrl>
#include <QFile>
#include <QtextStream>
#include <QMimeData>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    setAcceptDrops(true); //假如这行代码后，主窗口就可以接收放下事件了
}

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

//拖动进入事件
void MainWindow::dragEnterEvent(QDragEnterEvent *event)
{
    if(event->mimeData()->hasUrls())    //数据中是否包含URL
        event->acceptProposedAction();  //接收
    else
        event->ignore();                //忽略
}

//放下事件
void MainWindow::dropEvent(QDropEvent *event)
{
    const QMimeData * mimeData = event->mimeData(); //获取MIME数据
    if(mimeData->hasUrls())
    {
        QList<QUrl> urlList = mimeData->urls();
        QString fileName=urlList.at(0).toLocalFile();
        if(!fileName.isEmpty())
        {
            QFile file(fileName);   //建立QFile对象，以只读方式打开文件
            if(!file.open(QIODevice::ReadOnly))
                return;
            QTextStream in(&file);      //建立文本流对象
            ui->textEdit->setText(in.readAll());
        }
    }
}

protected:
    void mousePressEvent(QMouseEvent *event);       //鼠标按下事件
    void dragEnterEvent(QDragEnterEvent *event);    //拖动进入事件
    void dragMoveEvent(QDragMoveEvent *event);      //拖动事件
    void dropEvent(QDropEvent *event);              //放下事件

#include "mainwindow.h"
#include <QLabel>
#include "ui_mainwindow.h"
#include <QMouseEvent>
#include <QDrag>
#include <QDragEnterEvent>
#include <QDragMoveEvent>
#include <QDropEvent>
#include <QPainter>
#include <QMimeData>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    setAcceptDrops(true);                       //设置窗口部件可以接收拖入
    QLabel * label = new QLabel(this);
    QPixmap pix("..//imagedragdrop/loGo.png");
    label->setPixmap(pix);
    label->resize(pix.size());
    label->move(100,100);
    label->setAttribute(Qt::WA_DeleteOnClose);  //当窗口关闭时销毁图片
}

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

//鼠标按下事件
void MainWindow::mousePressEvent(QMouseEvent *event)
{
    //第1步：获取图片
    //将鼠标指针所在位置的部件强制转换为Label类型
    QLabel * child = static_cast<QLabel *>(childAt(event->pos()));
    if(!child->inherits("QLabel"))
        return;
    QPixmap pixmap = *child->pixmap();

    //第2步：自定义MIME类型
    QByteArray itemData;
    QDataStream dataStream(&itemData,QIODevice::WriteOnly);
    //将图片信息，位置信息输入到自己数组中
    dataStream<<pixmap<<QPoint(event->pos()-child->pos());

    //第3步：将数据放入QMimeData中
    QMimeData *mimeData = new QMimeData;
    //将字节数组放入QMimeData中，这里的MIME类型是我们自己定义的
    mimeData->setData("myimage/png",itemData);

    //第4步：将QMimeData数据放入QDrag中
    QDrag *drag = new QDrag(this);      //创建QDrag用来移动数据
    drag->setMimeData(mimeData);
    drag->setPixmap(pixmap);            //在移动过程中显示图片，若不设置则默认显示一个小矩形
    drag->setHotSpot(event->pos()-child->pos());    //拖动时鼠标指针的位置不变

    //第5步：给原图添加阴影
    QPixmap tempPixmap = pixmap;
    QPainter painter;
    painter.begin(&tempPixmap);
    //在图片的外接矩形中添加一层透明的淡黑色形成阴影效果
    painter.fillRect(pixmap.rect(),QColor(127,127,127,127));
    painter.end();
    child->setPixmap(tempPixmap);       //在移动图片过程中，让原图片有一层黑色阴影

    //第6步：执行拖放操作
    if(drag->exec(Qt::CopyAction|Qt::MoveAction,Qt::CopyAction)==Qt::MoveAction)
    {
        child->close();             //如果是移动操作，那么拖放完成后关闭原标签
    }
    else
    {
        child->show();              //如果是复制操作，那么拖放完成后显示标签
        child->setPixmap(pixmap);   //显示原图片，不再使用阴影
    }

}

//拖入事件
void MainWindow::dragEnterEvent(QDragEnterEvent *event)
{
    if(event->mimeData()->hasFORMat("myimage/png"))
    {
        event->setDropAction(Qt::MoveAction);
        event->accept();
    }
    else
    {
        event->ignore();
    }
}

//拖动事件
void MainWindow::dragMoveEvent(QDragMoveEvent *event)
{
    if(event->mimeData()->hasFormat("myimage/png"))
    {
        event->setDropAction(Qt::MoveAction);
        event->accept();
    }
    else
    {
        event->ignore();
    }
}

//放下事件
void MainWindow::dropEvent(QDropEvent *event)
{
    if(event->mimeData()->hasFormat("myimage/png"))
    {
        QByteArray itemData = event->mimeData()->data("myimage/png");
        QDataStream dataStream(&itemData,QIODevice::ReadOnly);
        QPixmap pixmap;
        QPoint offset;
        dataStream>>pixmap>>offset;
        QLabel * newLabel = new QLabel(this);
        newLabel->setPixmap(pixmap);
        newLabel->resize(pixmap.size());
        newLabel->move(event->pos()-offset);
        newLabel->show();
        newLabel->setAttribute(Qt::WA_DeleteOnClose);  //当窗口关闭时销毁图片
        event->setDropAction(Qt::MoveAction);
        event->accept();
    }
    else
    {
        event->ignore();
    }
}

QT += printsupport

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
class QPrinter;

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private:
    Ui::MainWindow *ui;

private slots:
    void doPrint();
    void doPrintPreview();
    void printPreview(QPrinter *printer);
    void createpdf();

};

#endif // MAINWINDOW_H

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QPrinter>
#include <QPrintDialog>
#include <QPrintPreviewDialog>
#include <QFileDialog>
#include <QFileInfo>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    QAction *action_print = new QAction(tr("打印"),this);
    QAction *action_printPreview = new QAction(tr("打印预览"),this);
    QAction *action_pdf = new QAction(tr("生成pdf"),this);
    connect(action_print,SIGNAL(triggered()),this,SLOT(doPrint()));
    connect(action_printPreview,SIGNAL(triggered()),this,SLOT(doPrintPreview()));
    connect(action_pdf,SIGNAL(triggered()),this,SLOT(createPdf()));
    ui->mainToolBar->addAction(action_print);
    ui->mainToolBar->addAction(action_printPreview);
    ui->mainToolBar->addAction(action_pdf);

}

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

void MainWindow::doPrint()                    // 打印
{
    QPrinter printer;                         // 创建打印机对象
    QPrintDialog dlg(&printer, this);         // 创建打印对话框
    // 如果编辑器中有选中区域，则打印选中区域
    if (ui->textEdit->textCursor().hasSelection())
        dlg.addEnabledOption(QAbstractPrintDialog::PrintSelection);
    if (dlg.exec() == QDialog::Accepted) {    // 如果在对话框中按下了打印按钮
        ui->textEdit->print(&printer);        // 则执行打印操作
    }
}

void MainWindow::doPrintPreview()                    // 打印预览
{
    QPrinter printer;
    QPrintPreviewDialog preview(&printer, this);     // 创建打印预览对话框
    // 当要生成预览页面时，发射paintRequested()信号
    connect(&preview, &QPrintPreviewDialog::paintRequested,
            this, &MainWindow::printPreview);
    preview.exec();
}

void MainWindow::printPreview(QPrinter *printer)
{
    ui->textEdit->print(printer);
}

void MainWindow::createPdf()                // 生成PDF文件
{
    QString fileName = QFileDialog::getSaveFileName(this, tr("导出PDF文件"),
                                                    QString(), "*.pdf");
    if (!fileName.isEmpty()) {
        if (QFileInfo(fileName).suffix().isEmpty())
            fileName.append(".pdf");        // 如果文件后缀为空，则默认使用.pdf
        QPrinter printer;
        printer.setOutputFormat(QPrinter::PdfFormat);    // 指定输出格式为pdf
        printer.setOutputFileName(fileName);
        ui->textEdit->print(&printer);
    }
}