Qt4.4.3自带教程-一个变化牵扯其他的变化

#ifndef __LCDRANGE_H__ 
#define __LCDRANGE_H__ 
 
#include <QWidget> 
 
class QSlider; //new:提前声明一下 
 
class LCDRange :  public QWidget 
{ 
  Q_OBJECT 
public: 
        LCDRange(QWidget *parent = 0); 
         int value()  const; //new : 添加一个函数 
public slots: 
   void setValue( int value); 
signals: 
   void valueChanged( int newValue);     
private: 
  QSlider * slider; //new:改成成员变量 
}; 
 
#endif  // __LCDRANGE_H__

#include <QLCDNumber> 
#include <QSlider> 
#include <QVBoxLayout> 
 
 
#include  "lcdrange.h" 
 
LCDRange::LCDRange(QWidget *parent) 
        : QWidget(parent) 
{ 
   //LCD数字 
        QLCDNumber *lcd =  new QLCDNumber(2); 
        lcd->setSegmentStyle(QLCDNumber::Flat); 
 
   //Slider 
        slider =  new QSlider(Qt::Horizontal); 
        slider->setRange(0, 99); 
        slider->setValue(0); 
        connect(slider, SIGNAL(valueChanged( int)),lcd, SLOT(display( int))); 
         
         //new: 新加 
        connect(slider,SIGNAL(valueChanged( int)), this,SIGNAL(valueChanged( int))); 
 
   //布局 
        QVBoxLayout *layout =  new QVBoxLayout; 
        layout->addWidget(lcd); 
        layout->addWidget(slider); 
        setLayout(layout); 
} 
 
int LCDRange::value()  const 
{ 
   return slider->value(); 
} 
 
void LCDRange::setValue( int value) 
{ 
  slider->setValue(value); 
}

#ifndef __MYWIDGET_H__ 
#define __MYWIDGET_H__ 
#include <QWidget> 
 
class MyWidget :  public QWidget 
{ 
public: 
        MyWidget(QWidget *parent = 0); 
}; 
 
#endif  // __MYWIDGET_H__

#include <QApplication> 
#include <QPushButton> 
#include <QFont> 
#include <QGridLayout> 
 
#include  "lcdrange.h" 
#include  "mywidget.h" 
 
//MyWidget类实现部分 
MyWidget::MyWidget(QWidget *parent) 
        : QWidget(parent) 
{ 
   //创建quit按钮 
        QPushButton *quit =  new QPushButton(tr( "Quit")); 
        quit->setFont(QFont( "Times", 18, QFont::Bold)); 
        connect(quit, SIGNAL(clicked()), qApp, SLOT(quit())); 
         
        LCDRange* prevRange=0; 
 
   //网格布局 
        QGridLayout *grid =  new QGridLayout; 
         for ( int row = 0; row < 3; ++row) { 
                 for ( int column = 0; column < 3; ++column) { 
                        LCDRange *lcdRange =  new LCDRange; //创建LCD+Slider 
                        grid->addWidget(lcdRange, row, column); 
                                         
                         //new : 新增 
                         if(prevRange) 
                        { 
                           //如果存在前一个 
                          connect(lcdRange,SIGNAL(valueChanged( int)),prevRange,SLOT(setValue( int))); 
                        } 
                        prevRange=lcdRange;                         
                } 
        } 
 
        QVBoxLayout *layout =  new QVBoxLayout; 
        layout->addWidget(quit); 
        layout->addLayout(grid); //子布局 
         
        setLayout(layout); //设置布局 
} 

//主程序文件 
#include <QApplication> 
#include  "mywidget.h" 
 
int main( int argc,  char *argv[]) 
{ 
        QApplication app(argc, argv); 
         
         //创建MyWidget的一个实例 
        MyWidget widget; 
        widget.show(); 
         
         return app.exec(); 
}