76.QT槽的机制

• 按钮点击获取文本框输入

   void Dialog::on_pushButton_clicked()
   {
       //获取文本输入
       QString vstr = ui->lineEdit->text();
  
       //判断是否转换成功
       bool isok;
       //转换
       int value = vstr.toInt(&isok);
       double area = value*value*PI;
       QString tempstr;
       ui->lineEdit_2->setText(tempstr.setNum(area));
   }

• 文本框内容改变执行的操作

  void Dialog::on_lineEdit_textChanged(const QString &arg1)
  {
      this->on_pushButton_clicked();
  }

手动实现QT的界面

• dialog.h添加按钮,文本框,标签等头文件

   #include <QDialog>
   #include <QPushButton>
   #include <QLineEdit>
   #include <QLabel>

• 在dialog.h类中添加按钮,文本框,标签的指针,并添加按钮的触发函数

   private:
       Ui::Dialog *ui;
       //图形控件
       QLabel *label1,*label2;
       QLineEdit *edit1,*edit2;
       QPushButton *button;
  
   //触发机制
   private slots:
       void showit();

• 在dialog.cpp中初始化,并创建布局
• 创建布局头文件

   #include "QGridLayout"//布局

• 初始化

   //加上this显示在当前窗口
       button = new QPushButton(this);
       button->setText(tr("计算"));
       //button->show();
       button->resize(,);
  
       edit1 = new QLineEdit(this);
  
       edit2 = new QLineEdit(this);
  
       label1 = new QLabel(this);
  
       label1->setText("输入半径:");
  
       label2 = new QLabel(this);
  
       label2->setText("输出面积:");

• 创建布局

    //网格布局
       QGridLayout *mylayout = new QGridLayout(this);
       mylayout->addWidget(label1,,);
       mylayout->addWidget(label2,,);
       mylayout->addWidget(edit1,,);
       mylayout->addWidget(edit2,,);
       mylayout->addWidget(button,,);

• 关联按钮的函数或者文本框变化的函数

    //clicked触发         关联
       connect(button,SIGNAL(clicked(bool)),this,SLOT(showit()));
       connect(edit1,SIGNAL(textChanged(QString)),this,SLOT(showit()));

• 按钮点击函数实现

   void Dialog::showit()
   {
       //获取文本输入
       QString vstr = edit1->text();
  
       //判断是否转换成功
       bool isok;
       //转换
       int value = vstr.toInt(&isok);
       double area = value*value*PI;
       QString tempstr;
       edit2->setText(tempstr.setNum(area));
   }

---

完整代码:

• dialog.h

   #ifndef DIALOG_H
   #define DIALOG_H
  
   #include <QDialog>
   #include <QPushButton>
   #include <QLineEdit>
   #include <QLabel>
  
   namespace Ui {
   class Dialog;
   }
  
   class Dialog : public QDialog
   {
       Q_OBJECT
  
   public:
       explicit Dialog(QWidget *parent = );
       ~Dialog();
  
   private:
       Ui::Dialog *ui;
       //图形控件
       QLabel *label1,*label2;
       QLineEdit *edit1,*edit2;
       QPushButton *button;
  
   //触发机制
   private slots:
       void showit();
   };
  
   #endif // DIALOG_H

• dialog.cpp

   #include "dialog.h"
   #include "ui_dialog.h"
   #include "QGridLayout"//布局
   #define PI 3.14159
  
   Dialog::Dialog(QWidget *parent) :
       QDialog(parent),
       ui(new Ui::Dialog)
   {
       //加上this显示在当前窗口
       button = new QPushButton(this);
       button->setText(tr("计算"));
       //button->show();
       button->resize(,);
  
       edit1 = new QLineEdit(this);
  
       edit2 = new QLineEdit(this);
  
       label1 = new QLabel(this);
  
       label1->setText("输入半径:");
  
       label2 = new QLabel(this);
  
       label2->setText("输出面积:");
  
       //网格布局
       QGridLayout *mylayout = new QGridLayout(this);
       mylayout->addWidget(label1,,);
       mylayout->addWidget(label2,,);
       mylayout->addWidget(edit1,,);
       mylayout->addWidget(edit2,,);
       mylayout->addWidget(button,,);
  
       //clicked触发         关联
       connect(button,SIGNAL(clicked(bool)),this,SLOT(showit()));
       connect(edit1,SIGNAL(textChanged(QString)),this,SLOT(showit()));
       ui->setupUi(this);
   }
  
   Dialog::~Dialog()
   {
       delete ui;
   }
  
   void Dialog::showit()
   {
       //获取文本输入
       QString vstr = edit1->text();
  
       //判断是否转换成功
       bool isok;
       //转换
       int value = vstr.toInt(&isok);
       double area = value*value*PI;
       QString tempstr;
       edit2->setText(tempstr.setNum(area));
   }

• main.cpp

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