Qt中事件的传递

• 新建Qt Gui项目，基类选择QWidget
• 添加新文件，基于C++类，类名MyLineEdit
• mylineedit.h中代码：
• #ifndef MYLINEEDIT_H
  #define MYLINEEDIT_H
  
  #include <QLineEdit>
  
  class MyLineEdit : public QLineEdit
  {
      Q_OBJECT
  public:
      explicit MyLineEdit(QWidget *parent = 0);
      bool event(QEvent *event);
      
  signals:
      
  public slots:
  protected:
      void keyPressEvent(QKeyEvent *event);
      
  };
  //void MyLineEdit::keyPressEvent()
  
  #endif // MYLINEEDIT_H
  
  
  
• mylineedit.cpp中代码：

#include "mylineedit.h"
#include <QDebug>
#include <QKeyEvent>

MyLineEdit::MyLineEdit(QWidget *parent) :
    QLineEdit(parent)
{
}

void MyLineEdit::keyPressEvent(QKeyEvent *event)
{
    //qDebug()<<tr("MyLineEdit键盘按下事件");
    QLineEdit::keyPressEvent(event);
    event->ignore();
}
bool MyLineEdit::event(QEvent *event)
{
    if(event->type()==QEvent::KeyPress)
        qDebug()<<tr("MyLineEdit的event函数");
    return QLineEdit::event(event);
}

• widget.h中代码：

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>

class MyLineEdit;
namespace Ui {
class Widget;
}

class Widget : public QWidget
{
    Q_OBJECT
    
public:
    explicit Widget(QWidget *parent = 0);
    ~Widget();
    bool eventFilter(QObject *obj,QEvent *event);

protected:
    void keyPressEvent(QKeyEvent *event);
    
private:
    Ui::Widget *ui;
    MyLineEdit *lineEdit;
};

#endif // WIDGET_H

• widget.cpp中代码：

#include "widget.h"
#include "ui_widget.h"
#include "mylineedit.h"
#include <QKeyEvent>
#include <QDebug>

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
    lineEdit=new MyLineEdit(this);
    lineEdit->move(100,100);
    lineEdit->installEventFilter(this);//在widget上为lineEdit安装事件过滤器

}
void Widget::keyPressEvent(QKeyEvent *event)
{
    qDebug()<<tr("Widget键盘按下事件");
}

bool Widget::eventFilter(QObject *obj,QEvent *event)
{
    if(obj==lineEdit)
        {
        if(event->type()==QEvent::KeyPress)
           qDebug()<<tr("widget的事件过滤器");
    }
    return QWidget::eventFilter(obj,event);
}
Widget::~Widget()
{
    delete ui;
}

• main.cpp中代码：

#include <QtGui/QApplication>
#include "widget.h"
#include <QTextCodec>

int main(int argc, char *argv[])
{
    QTextCodec::setCodecForTr(QTextCodec::codecForLocale());
    QApplication a(argc, argv);
    Widget w;
    w.show();    
    return a.exec();
}