如何单独捕捉QTreeWdiget鼠标点击事件

如何单独捕捉QTreeWdiget鼠标点击事件

首先肯定想到的是安装eventFilter

安装后发现收不到鼠标点击事件，很幸运有人解答了, 得用treewidget->viewport()安装事件过滤器。

.h

#ifndef OBSERVERMOUSECLICKED_H
#define OBSERVERMOUSECLICKED_H

#include <QWidget>

class ObserverMousePressed : public QWidget
{
    Q_OBJECT
public:
    explicit ObserverMousePressed(Qt::MouseButtons, QWidget *parent);

signals:
    void mousePressed();
public slots:

protected:
    virtual void mousePressEvent(QMouseEvent *event) override;
    virtual bool eventFilter(QObject *watched, QEvent *event) override;

private:
    QObject * m_pTarget = nullptr;
    Qt::MouseButtons m_buttons;
};

#endif // OBSERVERMOUSECLICKED_H

.cpp

#include <QMouseEvent>
#include "observermousepressed.h"

ObserverMousePressed::ObserverMousePressed(Qt::MouseButtons buttons,QWidget *parent) :
    QWidget(parent), m_pTarget(parent),m_buttons(buttons)
{
    Q_ASSERT(parent);
    parent->installEventFilter(this);
    this->setVisible(false);
}

void ObserverMousePressed::mousePressEvent(QMouseEvent *event)
{
    QWidget::mousePressEvent(event);
}

bool ObserverMousePressed::eventFilter(QObject *watched, QEvent *event)
{
    if(watched == m_pTarget)
    {
        if(event->type() == QEvent::MouseButtonPress)
        {
            if(reinterpret_cast<QMouseEvent *>(event)->buttons() == m_buttons )
            {
                emit mousePressed();
                QWidget::eventFilter(watched, event);
                return false;
            }
        }
    }
    return  QWidget::eventFilter(watched, event);
}

use case

ObserverMousePressed *pProjectTreeLeftButtonPressed 
= new ObserverMousePressed(Qt::LeftButton, ui->treeWidget_project->viewport());

如何得知鼠标点击的Item呢

我们知道eventFilter的调用位置是在事件函数之前的，这导致没法通过currentItem()方法得到当前点击的Item，因为currentItemchanged信号是在点击事件函数之后发出的，所以需要在eventFilter发出mousePressed信号后，获取鼠标点击处的Item。
这里有个小坑

   connect(pProjectTreeLeftButtonPressed, &ObserverMousePressed::mousePressed,[=](){
	 	ui->treeWidget_project->setCurrentItem(ui->treeWidget_project->itemAt(ui->treeWidget_project->viewport()->mapFromGlobal(QCursor::pos())));
	 	ui->treeWidget_project->currentItem();
	 	....
    });

有什么用

如构造函数 explicit ObserverMousePressed(Qt::MouseButtons, QWidget *parent);所示, 通过判断Qt::MouseButtons我们可以定向的检索到底是鼠标的哪些建点击的这个Item了;
因为QTreeWidget无论是左键点击还是右键点击, 都会触发currentItemChanged信号, 这会导致逻辑处理无法分化, 比如我们希望左键点击时刷新对应的属性视图, 右键单击时显示右键action菜单但是不刷新对应的属性视图,这种需求就无法实现.