How to resolve the algorithm GUI enabling/disabling of controls step by step in the C++ programming language

Published on 7 June 2024 03:52 AM
#cpp

How to resolve the algorithm GUI enabling/disabling of controls step by step in the C++ programming language

Table of Contents

Problem Statement

In addition to fundamental GUI component interaction, an application should dynamically enable and disable GUI components, to give some guidance to the user, and prohibit (inter)actions which are inappropriate in the current state of the application.

Similar to the task GUI component interaction, write a program that presents a form with three components to the user:

The field is initialized to zero. The user may manually enter a new value into the field, increment its value with the "increment" button, or decrement the value with the "decrement" button. The input field should be enabled only when its value is zero. The "increment" button only as long as the field's value is less then 10: When the value 10 is reached, the button should go into a disabled state. Analogously, the "decrement" button should be enabled only as long as the value is greater than zero. Effectively, the user can now either increment up to 10, or down to zero. Manually entering values outside that range is still legal, but the buttons should reflect that and enable/disable accordingly.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm GUI enabling/disabling of controls step by step in the C++ programming language

Class Definition MyWidget:

  • A custom widget derived from QWidget. It contains the graphical user interface elements and the logic for handling user interactions.

Constructor MyWidget::MyWidget:

  • Initializes the custom widget.
  • Sets up the layout using QVBoxLayout and QHBoxLayout.
  • Creates labels, buttons, and a line edit widget for user input.
  • Establishes connections between GUI elements and defined slots (event handlers).

Slot MyWidget::buttonChange:

  • Called when the text in the line edit widget changes.
  • Checks if the entered text is a number between 1 and 10.
  • Enables or disables the "Increment" and "Decrement" buttons based on the entered number.

Slot MyWidget::addField:

  • Called when the "Increment" button is clicked.
  • Increments the number in the line edit widget.

Slot MyWidget::subtractField:

  • Called when the "Decrement" button is clicked.
  • Decrements the number in the line edit widget.

Main Function main:

  • Initializes the Qt application with QApplication.
  • Creates an instance of the custom widget MyWidget.
  • Shows the widget and starts the application event loop with app.exec().

Usage:

  • The widget displays an instruction label and a line edit widget for the user to enter a number between 1 and 10.
  • If the entered number is above 10, the "Decrement" button is enabled, and the "Increment" button is disabled.
  • If the entered number is below 1, the "Increment" button is enabled, and the "Decrement" button is disabled.
  • The "Increment" button increments the entered number by 1, while the "Decrement" button decrements it by 1.

Source code in the cpp programming language

#ifndef TASK_H
#define TASK_H

#include <QWidget>

class QPushButton ;
class QString ;
class QLineEdit ;
class QLabel ;
class QVBoxLayout ;
class QHBoxLayout ;

class MyWidget : public QWidget {
    
    Q_OBJECT
public:
   MyWidget( QWidget *parent = 0 ) ;
private slots:
   void buttonChange( const QString & ) ;
   void addField( ) ;
   void subtractField( ) ;
private :
   QVBoxLayout *thisWidgetLayout ;
   QLabel *instruction ;
   QPushButton *increment ;
   QPushButton *decrement ;
   QLineEdit *entryField ;
   QHBoxLayout *lowerPart ;
} ;
#endif


#include <QtGui>
#include <QString>
#include "task.h" 

MyWidget::MyWidget ( QWidget *parent ) 
   : QWidget( parent ) {
   thisWidgetLayout = new QVBoxLayout ( this )  ;
   instruction = new QLabel ;
   instruction->setText( "Enter a number between 1 and 10 ! Numbers above 10 are decremented, below 0 incremented!" ) ;
   instruction->setWordWrap( true ) ;
   lowerPart = new QHBoxLayout ;
   entryField = new QLineEdit( "0" ) ;
   increment = new QPushButton( "Increment" ) ;
   decrement = new QPushButton( "Decrement" ) ;
   increment->setDefault( true ) ;
   connect( entryField , SIGNAL ( textChanged ( const QString &  ) ) , 
	    this , SLOT ( buttonChange( const QString & )) ) ;
   connect( entryField , SIGNAL ( textEdited ( const QString &  ) ) , 
	    this , SLOT ( buttonChange( const QString & )) ) ;
   connect( increment , SIGNAL ( clicked( ) ) , this ,
	 SLOT ( addField( ) )) ;
   connect( decrement , SIGNAL ( clicked( ) ) , this ,
	 SLOT ( subtractField( ))) ;
   lowerPart->addWidget( entryField ) ;
   lowerPart->addWidget( increment ) ;
   lowerPart->addWidget( decrement ) ;
   thisWidgetLayout->addWidget( instruction ) ;
   thisWidgetLayout->addLayout( lowerPart ) ;
   setLayout( thisWidgetLayout ) ;
}

void MyWidget::buttonChange( const QString & text ) {
   bool ok ;
   increment->setEnabled( text.toInt( &ok, 10 ) < 10 ) ;
   increment->setDisabled( text.toInt( &ok, 10 ) > 9 ) ;
   decrement->setEnabled( text.toInt( &ok, 10 ) > 0 ) ;
   decrement->setDisabled( text.toInt( &ok, 10 ) <= 0 ) ;
   if ( ! ( text == "0" ) ) 
      entryField->setReadOnly( true ) ;
}

void MyWidget::addField( ) { 
   bool ok ;
   int number = entryField->text( ).toInt( &ok , 10 ) ;
   number++ ;
   entryField->setText( QString("%1").arg( number )) ;
}

void MyWidget::subtractField( ) {
   bool ok ;
   int number = entryField->text( ).toInt( &ok , 10 ) ;
   number-- ;
   entryField->setText( QString("%1").arg( number )) ;
}


#include <QApplication>
#include "task.h"

int main( int argc, char *argv[ ] ) {
   QApplication app( argc , argv ) ;
   MyWidget theWidget ;
   theWidget.show( ) ;
   return app.exec( ) ;
}

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