Dialog_01

Dialog.pro

+QT       += core gui
+
+greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
+
+CONFIG += c++11
+
+# The following define makes your compiler emit warnings if you use
+# any Qt feature that has been marked deprecated (the exact warnings
+# depend on your compiler). Please consult the documentation of the
+# deprecated API in order to know how to port your code away from it.
+DEFINES += QT_DEPRECATED_WARNINGS
+
+# You can also make your code fail to compile if it uses deprecated APIs.
+# In order to do so, uncomment the following line.
+# You can also select to disable deprecated APIs only up to a certain version of Qt.
+#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0
+
+SOURCES += \
+    main.cpp \
+    dialog.cpp
+
+HEADERS += \
+    dialog.h
+
+FORMS += \
+    dialog.ui
+
+TRANSLATIONS += \
+    Dialog_zh_CN.ts
+
+# Default rules for deployment.
+qnx: target.path = /tmp/$${TARGET}/bin
+else: unix:!android: target.path = /opt/$${TARGET}/bin
+!isEmpty(target.path): INSTALLS += target

Dialog_zh_CN.ts

+<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE TS>
+<TS version="2.1" language="Dialog_zh_CN"></TS>

dialog.cpp

+#include "dialog.h"
+#include "ui_dialog.h"
+
+const static double PI=3.1416;
+
+Dialog::Dialog(QWidget *parent)
+    : QDialog(parent)
+    , ui(new Ui::Dialog)
+{
+    ui->setupUi(this);
+}
+
+Dialog::~Dialog()
+{
+    delete ui;
+}
+
+
+void Dialog::on_countBtn_clicked()
+{
+    bool ok;
+    QString tempStr;
+    QString valueStr=ui->radiusLineEdit->text();
+    int valueInt=valueStr.toInt(&ok);
+    double area=valueInt*valueInt*PI;
+    ui->areaLabel_2->setText(tempStr.setNum(area));
+}
+
+void Dialog::on_radiusLineEdit_textChanged(const QString &arg1)
+{
+    bool ok;
+    QString tempStr;
+    QString valueStr=ui->radiusLineEdit->text();
+    int valueInt=valueStr.toInt(&ok);
+    double area=valueInt*valueInt*PI;
+    ui->areaLabel_2->setText(tempStr.setNum(area));
+}

dialog.h

+#ifndef DIALOG_H
+#define DIALOG_H
+
+#include <QDialog>
+
+QT_BEGIN_NAMESPACE
+namespace Ui { class Dialog; }
+QT_END_NAMESPACE
+
+class Dialog : public QDialog
+{
+    Q_OBJECT
+
+public:
+    Dialog(QWidget *parent = nullptr);
+    ~Dialog();
+
+private slots:
+    void on_countBtn_clicked();
+
+    void on_radiusLineEdit_textChanged(const QString &arg1);
+
+private:
+    Ui::Dialog *ui;
+};
+#endif // DIALOG_H

dialog.ui

+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>Dialog</class>
+ <widget class="QDialog" name="Dialog">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>603</width>
+    <height>191</height>
+   </rect>
+  </property>
+  <property name="windowTitle">
+   <string>Dialog</string>
+  </property>
+  <widget class="QLabel" name="radiusLabel">
+   <property name="geometry">
+    <rect>
+     <x>50</x>
+     <y>50</y>
+     <width>91</width>
+     <height>31</height>
+    </rect>
+   </property>
+   <property name="text">
+    <string>半径</string>
+   </property>
+  </widget>
+  <widget class="QLabel" name="areaLabel_1">
+   <property name="geometry">
+    <rect>
+     <x>360</x>
+     <y>50</y>
+     <width>101</width>
+     <height>31</height>
+    </rect>
+   </property>
+   <property name="text">
+    <string>面积</string>
+   </property>
+  </widget>
+  <widget class="QLabel" name="areaLabel_2">
+   <property name="geometry">
+    <rect>
+     <x>450</x>
+     <y>50</y>
+     <width>101</width>
+     <height>31</height>
+    </rect>
+   </property>
+   <property name="frameShape">
+    <enum>QFrame::Panel</enum>
+   </property>
+   <property name="frameShadow">
+    <enum>QFrame::Sunken</enum>
+   </property>
+   <property name="text">
+    <string/>
+   </property>
+  </widget>
+  <widget class="QLineEdit" name="radiusLineEdit">
+   <property name="geometry">
+    <rect>
+     <x>160</x>
+     <y>50</y>
+     <width>121</width>
+     <height>31</height>
+    </rect>
+   </property>
+  </widget>
+  <widget class="QPushButton" name="countBtn">
+   <property name="geometry">
+    <rect>
+     <x>400</x>
+     <y>110</y>
+     <width>93</width>
+     <height>28</height>
+    </rect>
+   </property>
+   <property name="text">
+    <string>计算</string>
+   </property>
+   <property name="default">
+    <bool>false</bool>
+   </property>
+  </widget>
+ </widget>
+ <resources/>
+ <connections/>
+</ui>

main.cpp

+#include "dialog.h"
+
+#include <QApplication>
+
+int main(int argc, char *argv[])
+{
+    QApplication a(argc, argv);
+    Dialog w;
+    w.show();
+    return a.exec();
+}