[Fahrenheit <=> Celsius] Temperature Converter Tutorial using Qt Designer, Qt Creator

Choose Qt Creator Menu | File |New File or Project… | Qt Widget Project | Qt Gui Application.

Widget	Property	Value
MainWindowTempConverter	windowTitle	[Fahrenheit <=> Celsius] Temperature Converter
lineEditFahrenheit	None	None
lineEditCelsius	None	None
labelFahrenheit	text	Fahrenheit value:
labelCelsius	text	Celsius value:

Right click widget | Go to slot… | “Go to slot” window pops up | Select signal: returnPressed()

Widget, Slot	Signal	Implementation
lineEditFahrenheit	returnPressed()	See code below
lineEditCelsius	returnPressed()	See code below

void MainWindow::on_lineEditFahrenheit_returnPressed()

{

    QString strFahrenheit = ui->lineEditFahrenheit->text();  //try 212F = 100C

    double fahrenheit = strFahrenheit.toDouble();

    double celsius = (fahrenheit - 32)*5.0/9;

    qDebug() << celsius << endl; //needs to "#include <QtDebug>"

    QString strCelsius;

    strCelsius.setNum(celsius, 'f', 0);

    //f format is without E/10^.

    //zero is the precision where zero number of digits after the decimal point.

    // Other valid character formats are 'e', 'E', 'f', 'g' and 'G'.

    // 'g' is after E and F, g uses either e or f format.

    ui->lineEditCelsius->setText(strCelsius);

}

void MainWindow::on_lineEditCelsius_returnPressed()

{

    QString strCelsius = ui->lineEditCelsius->text();

    double celsius = strCelsius.toDouble();

    double fahrenheit = 9/5.0*celsius + 32;

    qDebug() << fahrenheit << endl;

    QString strFahrenheit;

    strFahrenheit.setNum(fahrenheit, 'f', 0);

    ui->lineEditFahrenheit->setText(strFahrenheit);

}

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