Qt焦点事件

为了尝试得到Qt窗口得到或者失去焦点的事件，使用了两种方法尝试：
方法一：重载窗口的 focusInEvent 和 focusOutEvent。
.h

protected:    virtual void focusInEvent(QFocusEvent * event);    virtual void focusOutEvent(QFocusEvent * event);

.cpp

void ShapeWindow::focusInEvent(QFocusEvent *){    qDebug()<<"show";    show();}void ShapeWindow::focusOutEvent(QFocusEvent *){    qDebug()<<"hide";    hide();}

方法二：使用 eventFilter 过滤。
.h

public slots:    bool eventFilter(QObject *watched, QEvent *event);

.cpp
初始化时安装事件过滤：

    ui->widget_shape->installEventFilter(this);    ui->widget_thick->installEventFilter(this);

过滤函数：

bool MainWindow::eventFilter(QObject *watched, QEvent *event){    qDebug()<<"eventFilter"<<event->type()<<endl;    if(watched == ui->widget_shape)    {        qDebug()<<"eventFilter widget_shape "<<event->type()<<endl;        if(event->type() == QEvent::FocusIn)        {          qDebug()<<"eventFilter widget_shape FocusIn"<<endl;            ;        }        else if(event->type() == QEvent::FocusOut)        {            qDebug()<<"eventFilter widget_shape FocusOut"<<endl;            ui->widget_shape->hide();        }    }    else if(watched == ui->widget_thick)    {        qDebug()<<"eventFilter widget_thick "<<event->type()<<endl;        if(event->type() == QEvent::FocusIn)        {            qDebug()<<"eventFilter widget_thick FocusIn"<<endl;            ;        }        else if(event->type() == QEvent::FocusOut)        {            qDebug()<<"eventFilter widget_thick FocusOut"<<endl;            ui->widget_thick->hide();        }    }    return QMainWindow::eventFilter(watched,event);}

widget默认是没有焦点的，此时使用上边两种方法都无法获取到焦点事件，需要设置窗口的 focusPolicy 属性，并在widget显示之后 setFocus()

void MainWindow::on_btn_thick_clicked()    //粗细{    ui->widget_shape->hide();    ui->widget_thick->show();    ui->widget_thick->setFocus();}