Creating a Qt C++ Application

Completing the Source File

Now that the header file is complete, move on to the source file, textfinder.cpp.

1. In the Projects view, double-click the textfinder.cpp file to open it for editing.
2. Add code to load a text file using QFile, read it with QTextStream, and then display it on textEdit with setPlainText(). This is illustrated by the following code snippet:

    void TextFinder::loadTextFile()
    {
        QFile inputFile(":/input.txt");
        inputFile.open(QIODevice::ReadOnly);
   
        QTextStream in(&inputFile);
        QString line = in.readAll();
        inputFile.close();
   
        ui->textEdit->setPlainText(line);
        QTextCursor cursor = ui->textEdit->textCursor();
        cursor.movePosition(QTextCursor::Start, QTextCursor::MoveAnchor, 1);
    }

3. To use QFile and QTextStream, add the following #includes to textfinder.cpp:

    #include <QtCore/QFile>
    #include <QtCore/QTextStream>

4. For the on_findButton_clicked() slot, add code to extract the search string and use the find() function to look for the search string within the text file. This is illustrated by the following code snippet:

    void TextFinder::on_findButton_clicked()
    {
        QString searchString = ui->lineEdit->text();
        ui->textEdit->find(searchString, QTextDocument::FindWholeWords);
    }

5. Once both of these functions are complete, add a line to call loadTextFile() in the constructor, as illustrated by the following code snippet:

    TextFinder::TextFinder(QWidget *parent)
        : QWidget(parent), ui(new Ui::TextFinder)
    {
        ui->setupUi(this);
        loadTextFile();
    }

The on_findButton_clicked() slot is called automatically in the uic generated ui_textfinder.h file by this line of code:

 QMetaObject::connectSlotsByName(TextFinder);