计算器表单

使用表单的创建采用 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 子类。

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.

预备

The user interface for this example is designed completely using Qt 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
					

当构建工程时， uic will create a header file that lets us construct the form.

CalculatorForm 类定义

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"
					

定义 CalculatorForm 类通过子类化 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 类实现

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);
}
					

用户界面的设置是采用 setupUI() 函数。我们传递 this 作为自变量到此函数以使用 CalculatorForm 小部件本身作为用户界面容器。

槽 updateResult() 添加值并在 outputwidget 设置结果：

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.

范例工程 @ code.qt.io

内容

• 预备

• CalculatorForm 类定义

• CalculatorForm 类实现