在 mousePressEvent 期间 Qt5/C++ 释放鼠标

Question

我有一个QGridLayout，其中每个单元格都包含我的自定义小部件QFrameExtended，定义如下：

在.h中：

#ifndef QFRAMEEXTENDED_H
#define QFRAMEEXTENDED_H

#include <QObject>
#include <QFrame>

class QFrameExtended : public QFrame
{
    Q_OBJECT

private:

public:
    int id;
    explicit QFrameExtended(QWidget *parent = 0);

signals:
    void mousePressEvent(QMouseEvent *);
    void mouseReleaseEvent(QMouseEvent *);
    void pressed(QFrameExtended *);
    void released(QFrameExtended *);

public slots:
    void on_mouse_press();
    void on_mouse_release();
};

#endif // QFRAMEEXTENDED_H

在 .cpp 中：

#include "qframe_extended.h"

QFrameExtended::QFrameExtended(QWidget *parent) : QFrame(parent)
{
    this->id = /* Imagine here there is a function to generate an id */ ;
    connect( this, SIGNAL( mousePressEvent(QMouseEvent*) ), this, SLOT( on_mouse_press() ) );
    connect( this, SIGNAL( mouseReleaseEvent(QMouseEvent*) ), this, SLOT( on_mouse_release() ) );
}

void QFrameExtended::on_mouse_press() {
    emit pressed(this);
}

void QFrameExtended::on_mouse_release() {
    emit released(this);
}

我的表单使用QFrameExtended 小部件创建QGridLayout，并为每个小部件定义一个事件处理程序：

/* ... */
/* This snippet of code is inside a loop that is creating frame objects */
connect(frame, &QFrameExtended::pressed, this, &MyForm::on_mouse_press);
connect(frame, &QFrameExtended::released, this, &MyForm::on_mouse_release);
/* ... */

最后是事件处理程序：

void MyForm::on_mouse_press(QFrameExtended *frame) {
    qDebug() << "Pressed here: " << frame->id << endl;
}

void MyForm::on_mouse_release(QFrameExtended *frame) {
    qDebug() << "Released here: " << frame->id << endl;
}

当我点击一个单元格（即 QFrameExtended 小部件）而不释放按钮时，我会看到控制台上打印了单元格的 id。在我将鼠标移到另一个单元格上后，当我释放按钮时，我会看到打印了第二个 id。

一个例子是这样的输出：

在这里按下：1

在这里发布：3

但实际情况是，当我在 QFrameExtended 上按下鼠标按钮时，他开始抓取所有鼠标事件，直到我释放按钮。这是预期的行为：

当在窗口小部件内按下鼠标按钮时，Qt 会自动抓取鼠标；小部件将继续接收鼠标事件，直到最后一个鼠标按钮被释放。

发件人：http://doc.qt.io/qt-4.8/qmouseevent.html

如何改变这种行为？如果你也能给我一个例子，我将不胜感激

Answer 1

好的，我按照 peppe 的提示解决了。我尝试扩展QGridLayout，但布局不支持鼠标事件，因为不继承自QWidget。所以，我扩展了包含布局的QWidget。

在.h中：

#ifndef QWIDGETEXTENDED_H
#define QWIDGETEXTENDED_H

#include <QWidget>
#include <QString>
#include <QMouseEvent>
#include "qframe_extended.h"

class QWidgetExtended : public QWidget
{
    Q_OBJECT
public:
    explicit QWidgetExtended(QWidget *parent = 0);

protected:
    virtual void mousePressEvent(QMouseEvent *);
    virtual void mouseReleaseEvent(QMouseEvent *);

signals:
    void pressed(QFrameExtended *);
    void released(QFrameExtended *);

};

#endif

在 .cpp 中：

#include "qwidget_extended.h"
#include "qframe_extended.h"

QWidgetExtended::QWidgetExtended(QWidget *parent) : QWidget(parent)
{

}

void QWidgetExtended::mousePressEvent(QMouseEvent *event) {
    QFrameExtended frame;
    QWidget *widget = this->childAt(event->pos());
    if (widget != NULL) {
        QString widgetClassName(widget->metaObject()->className());
        //I don't use explicitly the string because if one day someone changes the name of the class, the compiler will output an error
        QString className(frame.metaObject()->className());
        if (widgetClassName == className) {
            emit pressed(dynamic_cast<QFrameExtended*> (widget));
        }
    }
}

void QWidgetExtended::mouseReleaseEvent(QMouseEvent *event) {
    QFrameExtended frame;
    QWidget *widget = this->childAt(event->pos());
    if (widget != NULL) {
        QString widgetClassName(widget->metaObject()->className());
        //I don't use explicitly the string because if one day someone changes the name of the class, the compiler will output an error
        QString className(frame.metaObject()->className());
        if (widgetClassName == className) {
            emit released(dynamic_cast<QFrameExtended*> (widget));
        }
    }
}