A simple Notepad (example) for QT programming

     Qt is a cross-platform, native development framework for all major operating systems, including Linux, Windows, Macs, Symbian, and Maemo. This article describes a simple notepad implemented under Windows with QT programming, which is interesting to learn about QT programming. I am also just in touch with QT programming, I think QT is relatively easy to learn in other languages.   This is my QT creator implementation of the simple Notepad: QQ mini version   local network chat software see QT Programming-my QQ (LAN available)-with the source code above the interface is implemented with QT  designer There is a small icon in front of the actionnew (new), moving in the toolbar, the above effect appears.           This just realizes a part of the function, you can look at the Mainwindow.h file

<span style = "font-size: 14px;"> # ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QFileDialog>
#include <QTextStream>
#include <QMessageBox>
#include <QDialog>
#include <QLineEdit>
#include <QPushButton>
#include <QVBoxLayout>
#include <QHBoxLayout>

namespace Ui {
    class MainWindow;
}

class MainWindow: public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow (QWidget * parent = 0);
    ~ MainWindow ();
    void changeTitle (const QString & filename);
    void openfile (const QString & filename);
    void savefile (const QString & filename);


private:
    Ui :: MainWindow * ui;
    QString curFile;
    QLineEdit * find_textLineEdit;

private slots:
    void show_findText ();
    void on_action_2_triggered (); // Find
    void on_plan_textEdit_copyAvailable (bool b);
    void on_plan_textEdit_textChanged ();
    void on_action_U_triggered (); // Undo
    void on_action_P_triggered (); // Paste
    void on_action_C_triggered (); // Copy
    void on_action_T_triggered (); // Cut
    void on_actionExit_triggered (); // Exit
    bool on_actionSave_triggered (); // Save
    bool on_actionSave_As_triggered (); // Save As
    void on_actionOpen_triggered (); // Open
    void on_actionNew_triggered (); // New
};

#endif // MAINWINDOW_H
</ span>

Main.h file

<span style= "FONT-SIZE:14PX;" > #include <QtGui/QApplication>
#include <QTextCodec>
#include "mainwindow.h"

int main ( int argc, char *argv[])
{
    qapplication A (argc, argv);

    Qtextcodec::setcodecforcstrings (Qtextcodec::codecforname ("GB2312"));
    Qtextcodec::setcodecforlocale (Qtextcodec::codecforname ("GB2312"));
    QTEXTCODEC::SETCODECFORTR (Qtextcodec::codecforname ("GB2312"));


    MainWindow W;
    W.show ();

    return a.exec ();
}
</span>

Mainwindow.cpp

<span style = "font-size: 14px;"> # include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QDebug>

MainWindow :: MainWindow (QWidget * parent):
    QMainWindow (parent),
    ui (new Ui :: MainWindow)
{
    ui-> setupUi (this);
    this-> changeTitle ("");
    this-> setCentralWidget (ui-> plan_textEdit);
    // Set the properties of the action
    ui-> action_T-> setEnabled (false);
    ui-> action_C-> setEnabled (false);
    // Set interface icon
  this-> setWindowIcon (QIcon (": / images / editor.png"));
}

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

void MainWindow :: savefile (const QString & filename)
{
    QFile file (filename);
    if (! file.open (QIODevice :: WriteOnly | QIODevice :: Text)) {
        QMessageBox :: warning (this, "Save",
                             tr ("Save, error?")
                             .arg (filename)
                            .arg (file.errorString ()));
        return;
    }
    QTextStream out (& file);
    out << ui-> plan_textEdit-> toPlainText ();
    file.close ();
}

void MainWindow :: openfile (const QString & filename)
{
    QFile file (filename);
    if (file.open (QIODevice :: ReadOnly | QIODevice :: Text)) {
        QMessageBox :: warning (this, "Open",
                             tr ("Save, error?")
                             .arg (filename)
                             .arg (file.errorString ()));
        return;
    }
    QTextStream in (& file);
    QString s = in.readAll ();
    ui-> plan_textEdit-> setPlainText (s);
}
void MainWindow :: changeTitle (const QString & filename)
{
    qDebug () << "***" << filename;
    if (filename.isEmpty ()) {
         this-> curFile = "";
         this-> setWindowTitle (tr ("Untitled.txt [*]-Notepad"));
    }
    else {
        this-> curFile = filename;
        QFileInfo fi (filename);
        QString name = fi.fileName ();
        this-> setWindowTitle (tr ("% 1 [*]-Notepad"). arg (name));
        qDebug () << "====" << name;
    }
    this-> setWindowModified (false);
    ui-> plan_textEdit-> document ()-> setModified (false);
}

void MainWindow :: on_actionNew_triggered () // New
{
    QTextDocument * document = ui-> plan_textEdit-> document ();
    if (! document-> isModified ()) {
        ui-> plan_textEdit-> setPlainText ("");
        this-> changeTitle ("");
        return;
    }
    int ret = QMessageBox :: question (this, "Save?",
                                  "disSave, Save",
                                  QMessageBox :: Save | QMessageBox :: Discard | QMessageBox :: Cancel);
    switch (ret)
    {
    case QMessageBox :: Cancel:

        break;
    case QMessageBox :: Discard:
        ui-> plan_textEdit-> setPlainText ("");
        this-> changeTitle ("");
        break;
    case QMessageBox :: Save:
          if (! on_actionSave_triggered ())
                 return;
          ui-> plan_textEdit-> setPlainText ("");
          this-> changeTitle ("");
          break;
         }

}

void MainWindow :: on_actionOpen_triggered () // Open
{
    QTextDocument * document = ui-> plan_textEdit-> document ();
    if (document-> isModified ()) {
        int ret = QMessageBox :: question (this, "Save?",
                                      "disSave, Save",
                                      QMessageBox :: Save | QMessageBox :: Discard | QMessageBox :: Cancel);
        if (ret == QMessageBox :: Cancel) {
            return;
        }
        else if (ret == QMessageBox :: Save) {

        }
    }
    // No modification Normal save Abandon save
    QString filename = QFileDialog :: getOpenFileName (this);
    if (filename.isEmpty ())
        return;
    this-> openfile (filename);
    this-> changeTitle (filename);
}

bool MainWindow :: on_actionSave_As_triggered () // Save as
{
    QString fileName = QFileDialog :: getSaveFileName (this, tr ("Save File"));
    if (fileName.isEmpty ())
        return false;
    this-> savefile (fileName);
    this-> changeTitle (fileName);
    return true;
}


bool MainWindow :: on_actionSave_triggered () // Save
{
    if (this-> curFile.isEmpty ())
     // qDebug () << "+++";
            return on_actionSave_As_triggered ();

    else
    {
        savefile (this-> curFile);
      this-> setWindowModified (false);
    }
    return true;
}

void MainWindow :: on_actionExit_triggered () // Exit
{
    this-> close ();
}

void MainWindow :: on_action_T_triggered () // cut
{
    this-> ui-> plan_textEdit-> cut ();
}

void MainWindow :: on_action_C_triggered () // Copy
{
    this-> ui-> plan_textEdit-> copy ();
}

void MainWindow :: on_action_P_triggered () // paste
{
    this-> ui-> plan_textEdit-> paste ();
}


void MainWindow :: on_action_U_triggered () // Undo
{
   this-> ui-> plan_textEdit-> undo ();
}

void MainWindow :: on_plan_textEdit_textChanged ()
{
    // qDebug () << "niaho";
    this-> setWindowModified (true);
}

void MainWindow :: on_plan_textEdit_copyAvailable (bool b)
{
    ui-> action_T-> setEnabled (b);
    ui-> action_C-> setEnabled (b);

}
// This part is implemented by coding, you can see what is different from the interface design
void MainWindow :: on_action_2_triggered () // Find
{
   QDialog * findDlg = new QDialog (this);
   findDlg-> setWindowTitle (tr ("Find!"));
   find_textLineEdit = new QLineEdit (findDlg);
   QPushButton * find_Bth = new QPushButton (tr ("Find next"), findDlg);

   QHBoxLayout * layout = new QHBoxLayout (findDlg);
   layout-> addWidget (find_textLineEdit);
   layout-> addWidget (find_Bth);

   findDlg-> show ();

    connect (find_Bth, SIGNAL (clicked ()), this, SLOT (show_findText ()));
}
void MainWindow :: show_findText ()
{
     QString findText = find_textLineEdit-> text ();
     if (! ui-> plan_textEdit-> find (findText, QTextDocument :: FindBackward))
     {
         QMessageBox :: warning (this, tr ("Find"), tr ("Cannot find% 1"). Arg (findText));
     }
}
</ span>

In fact, there is a part of the function is not realized, interested in the words can pay attention to my next article.