[QT] QT 5 procedure: print documents

Qt 5 Medium Qt Print Support The module provides support for printing .

The simplest , Just use one QPrinter Class and a print dialog QPrintDialog Class can complete the printing operation of the document .

Next, the program can print documents 、 Print preview and production PDF Document and other operations .

More applications can be found in the help by Qt Print Support Keyword view .

1、 Create a new one Qt Widgets application , The project name can be customized （ for example ：printFile）

Class names and base classes keep MainWindow and QMainWindow unchanged . After completion , open printFile.pro file , Add the following line of code ：

QT       += printsupport

2、 Then go to the design mode and drag a... Into the interface Text Edit . Until then mainwindow.h Add the pre declaration of the class in the file first ：

class QPrinter;

3、 Then add several slot function declarations ：

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

4、 The following to mainwindow.cpp Add header file to file ：

#include <QPrinter>
#include <QPrintDialog>
#include <QPrintPreviewDialog>
#include <QFileDialog>
#include <QFileInfo>

5、 Define several actions in the constructor ：

    QAction * action_print = new QAction(tr(" Print "),this);
    QAction * action_printPreview = new QAction(tr(" Print preview "),this);
    QAction * action_pdf = new QAction(tr(" Generate  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);

6、 Then add those Slot function The definition of ：

void MainWindow::doPrint()                          // Print 
{
    
    QPrinter printer;                               // Create printer object 
    QPrintDialog dlg(&printer,this);                // Create printer dialog 
    // If there is a selected area in the editor , Print the selected area 
    if(ui->textEdit->textCursor().hasSelection())
        dlg.addEnabledOption(QAbstractPrintDialog::PrintSelection);
    if(dlg.exec() == QDialog::Accepted){
                // If the print button is pressed in the dialog box 
        ui->textEdit->print(&printer);              // Then execute the printing operation 
    }
}

Here we first establish QPrinter Class object , It represents a printing device . Then a print dialog is created , If there is a selected area in the editor , Then print the area , Otherwise, print the entire page .

void MainWindow::doPrintPreview()                    // Print preview 
{
    
    QPrinter printer;
    QPrintPreviewDialog preview(&printer,this);      // Create print preview dialog box 
    // When you want to generate a preview page , launch paintRequested() The signal 
    connect(&preview,&QPrintPreviewDialog::paintRequested,this,&MainWindow::printPreview);

    preview.exec();
}

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

Here, the print preview dialog box is mainly used for print preview , To associate it paintRequested() Signal to the customized slot , The print function of the editor must be called in the slot , And with the coming QPrinter Class takes an object pointer as a parameter .

void MainWindow::createPdf()                            // Generate PDF file 
{
    
    QString fileName = QFileDialog::getSaveFileName(this,tr(" export PDF file "),QString(),"*.pdf");

    if(!fileName.isEmpty()){
    
        if(QFileInfo(fileName).suffix().isEmpty())
            fileName.append(".pdf");                    // If the file suffix is empty , It is used by default .pdf
        QPrinter printer;
        printer.setOutputFormat(QPrinter::PdfFormat);   // Specify the output format as  pdf
        printer.setOutputFileName(fileName);
        ui->textEdit->print(&printer);
    }
}

It's generating PDF In the slot of the document , Use the file dialog box to get the path to save the file ; If the file name does not specify a suffix , Then add “.pdf” suffix . And then to QPrinter Object to specify the output format and file path , This will print the document as PDF Format .

7、 Finally, you can run the program , If the computer has a printer installed , Then you can test the actual printing effect , Otherwise, it can only be tested PDF Printing effect .

Print preview dialog effect ：