Qt事件

原文链接：https://blog.csdn.net/yangyang031213/article/details/78584108

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);

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();
}