計算器錶單

Using a form created with Qt Designer in an application.

The Calculator Form Example shows how to use a form created with Qt Designer in an application by using the user interface information from a QWidget 子類。

Screenshot of the Calculator Form example

The example presents two spin boxes that are used to input integer values and a label that shows their sum. Whenever either of the spin boxes are updated, the signal-slot connections between the widgets and the form ensure that the label is also updated.

預備

The user interface for this example is designed completely using Qt Widgets Designer. The result is a UI file describing the form, the widgets used, any signal-slot connections between them, and other standard user interface properties.

To ensure that the example can use this file, we enable the CMAKE_AUTOUIC feature and list the UI file in the source files:

set(CMAKE_AUTOUIC ON)
qt_add_executable(calculatorform
    calculatorform.cpp calculatorform.h calculatorform.ui
    main.cpp
)

For qmake , we need to include a FORMS declaration in the example's project file:

FORMS       = calculatorform.ui

當構建工程時， uic will create a header file that lets us construct the form.

CalculatorForm 類定義

The CalculatorForm class uses the user interface described in the calculatorform.ui file. To access the form and its contents, we need to include the ui_calculatorform.h header file created by uic during the build process:

#include "ui_calculatorform.h"

定義 CalculatorForm 類通過子類化 QWidget because the form itself is based on QWidget :

class CalculatorForm : public QWidget
{
    Q_OBJECT
public:
    explicit CalculatorForm(QWidget *parent = nullptr);
private slots:
    void updateResult();
private:
    Ui::CalculatorForm ui;
};

Apart from the constructor, the class contains a private slot updateResult() that performs the calculation and updates the output widget accordingly. The private ui member variable refers to the form, and is used to access the contents of the user interface.

CalculatorForm 類實現

The constructor simply calls the base class's constructor, sets up the form's user interface and connects the signals QSpinBox::valueChanged () to the slot updateResult() .

CalculatorForm::CalculatorForm(QWidget *parent)
    : QWidget(parent)
{
    ui.setupUi(this);
    connect(ui.inputSpinBox1, &QSpinBox::valueChanged, this, &CalculatorForm::updateResult);
    connect(ui.inputSpinBox2, &QSpinBox::valueChanged, this, &CalculatorForm::updateResult);
}

用戶界麵的設置是采用 setupUI() 函數。我們傳遞 this 作為自變量到此函數以使用 CalculatorForm 小部件本身作為用戶界麵容器。

槽 updateResult() 添加值並在 outputwidget 設置結果：

void CalculatorForm::updateResult()
{
    const int sum = ui.inputSpinBox1->value() + ui.inputSpinBox2->value();
    ui.outputWidget->setText(QString::number(sum));
}

It is called whenever the value of one of the spin boxes changes.

範例工程 @ code.qt.io