1 介绍
事件过滤器是一种机制,当某个QObject没有所需要的事件功能时,可将其委托给其它QObject,通过eventFilter成员函数来过滤实现功能。
2 主要构成
委托:
ui->QObject1->installEventFilter(QObject2);eventFilter声明
virtual bool eventFilter(QObject *watched, QEvent *event) override;
在Qt creator中,可以使用如下步骤简化实现:
a)右键widget
b)选择insert Virtual。。。:
c)选择eventFilter,并勾选如下,稍后将定义粘贴到对应的.cpp文件中即可
3 示例代码:使用事件过滤器对label实现单双击事件响应
widget.cpp
#include "widget.h"
#include "ui_widget.h"
#include <QEvent>
Widget::Widget(QWidget *parent)
: QWidget(parent)
, ui(new Ui::Widget)
{
ui->setupUi(this);
//将label委托给widget
ui->labelSC->setText("单击我");
ui->labelSC->installEventFilter(this);
ui->labelDC->installEventFilter(this);
}
Widget::~Widget()
{
delete ui;
}
bool Widget::eventFilter(QObject *watched, QEvent *event)
{
if(watched == ui->labelSC)
{
if(event->type() == QEvent::Enter)
ui->labelSC->setStyleSheet("background-color:rgb(170,255,255)");
else if(event->type() == QEvent::Leave)
{
ui->labelSC->setText("单击我");
ui->labelSC->setStyleSheet("");
}
else if(event->type() == QEvent::MouseButtonPress)
ui->labelSC->setText("MouseButtonPress");
else if(event->type() == QEvent::MouseButtonRelease)
ui->labelSC->setText("MouseButtonRelease");
}
if(watched == ui->labelDC)
{
if(event->type() == QEvent::Enter)
ui->labelDC->setStyleSheet("background-color:rgb(170,0,255)");
else if(event->type() == QEvent::Leave)
{
ui->labelDC->setText("双击我");
ui->labelDC->setStyleSheet("");
}
else if(event->type() == QEvent::MouseButtonDblClick)
ui->labelDC->setText("MouseButtonDblClick");
else if(event->type() == QEvent::MouseButtonRelease)
ui->labelDC->setText("MouseButtonRelease");
}
return QWidget::eventFilter(watched, event);
}
widget.h
#ifndef WIDGET_H
#define WIDGET_H
#include <QWidget>
QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE
class Widget : public QWidget
{
Q_OBJECT
public:
Widget(QWidget *parent = nullptr);
~Widget();
private:
Ui::Widget *ui;
// QObject interface
public:
virtual bool eventFilter(QObject *watched, QEvent *event) override;
};
#endif // WIDGET_H
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