QT learning 08 set sail! First application instance

Qt Study 08 set sail ！ The first application example

Calculator program interface analysis

QLineEdit Components

• QLineEdit be used for Accept user input
• QLineEdit can Get user input string
• QLineEdit yes Functional components , The parent component is required as the container
• QLineEdit can Locate in the parent component

QWidget w;							//  Generate QWidget object , Top level components 
QLineEdit le(&w);					//  Generate QLineEdit object , Its parent component is QWidget
le.setAlignment(Qt::AlignRight);	//  Set the display string to the right 
le.move(10, 10);					//  Move to coordinates (10, 10)
le.resize(240, 30);					//  Set size width=240, height=30

Design and implementation

• Interface design

  • Define the spacing between components

    Space = 10px

  • Define the size of the button component

    Width = 40px,Height = 40px

  • Define the size of the text box component

    Width = 5 * 40px + 4 * 10px,Height = 30px

• The problem is
  • Calculator program Unwanted Maximize and minimize buttons
  • Calculator program window Should be Fixed size
  • The text box You cannot enter characters directly

#include <QtGui/QApplication>
#include <QWidget>
#include <QLineEdit>
#include <QPushButton>

int main(int argc, char *argv[])
{
    
    QApplication a(argc, argv);
    QWidget* w = new QWidget(NULL, Qt::WindowCloseButtonHint);
    QLineEdit* le = new QLineEdit(w);
    QPushButton* button[20] = {
    0};
    const char* btnText[20] =
    {
    
        "7", "8", "9", "+", "(",
        "4", "5", "6", "-", ")",
        "1", "2", "3", "*", "<-",
        "0", ".", "=", "/", "C",
    };
    int ret = 0;

    le->move(10, 10);
    le->resize(240, 30);
    le->setReadOnly(true);

    for(int i=0; i<4; i++)
    {
    
        for(int j=0; j<5; j++)
        {
    
            button[i*5 + j] = new QPushButton(w);
            button[i*5 + j]->resize(40, 40);
            button[i*5 + j]->move(10 + (10 + 40)*j, 50 + (10 + 40)*i);
            button[i*5 + j]->setText(btnText[i*5 + j]);
        }
    }

    w->show();
    w->setFixedSize(w->width(), w->height());
    
    ret = a.exec();

    delete w;

    return ret;
}

Summary

• GUI Before application development, you should The interface must be designed first
• GUI Application interface Every detail needs to be considered
  • The interface determines the end user experience
  • Interface details are GUI An important reflection of application quality
• Qt library Ability to achieve Various GUI Application requirements
  The interface must be designed first **
• GUI Application interface Every detail needs to be considered
  • The interface determines the end user experience
  • Interface details are GUI An important reflection of application quality
• Qt library Ability to achieve Various GUI Application requirements
• Qt Help document The use of is... For development It's very important Of