c++ - 在eventFilter触发之前发出对象的事件

Question

我想向对象添加事件。因此，我创建了一个实现eventFilter的类。

最小示例:

主窗口

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <iostream>

#include <QVBoxLayout>

#include "eventwatcher.cpp"
#include "mynewlineedit.cpp"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    QVBoxLayout *mainLay = new QVBoxLayout();

    MyNewLineEdit *lineEdit;

    for(int i = 0; i < 3; i++)
    {
        lineEdit = new MyNewLineEdit();
        mainLay->addWidget(lineEdit);
        new EventWatcher(lineEdit);
    }

    QWidget *centWid = new QWidget();
    centWid->setLayout(mainLay);

    setCentralWidget(centWid);
}



MainWindow::~MainWindow()
{
    delete ui;
}

eventwatcher.cpp:

#include <QWidget>
#include <QDebug>
#include <QKeyEvent>

#include <iostream>

class EventWatcher : public QObject
{
public:
   explicit EventWatcher(QWidget* parent = Q_NULLPTR) : QObject(parent)
   {
       if (parent)
       {
           parent->installEventFilter(this);
       }
   }

   virtual bool eventFilter(QObject*, QEvent* event) Q_DECL_OVERRIDE
   {
       if (event->type() == QEvent::KeyPress)
       {
           std::cout << "Pressed any key\n";
       }

       return false;
   }
};

mynewlineedit.cpp

#include <QLineEdit>
#include <iostream>

class MyNewLineEdit : public QLineEdit
{
public:
    MyNewLineEdit() : QLineEdit()
    {}

protected:
    void keyPressEvent(QKeyEvent *) Q_DECL_OVERRIDE
    {
        std::cout << "Event of the parent object\n";
    }
};

将 CONFIG += console添加到.pro文件

该项目是正常的Qt-Widgets-Application，其他所有文件均未修改。

结果如下:

Pressed any key

Event of the parent object

它本身的eventFilter可以正常工作。但是事件处理的顺序存在问题。

在触发父对象的KeyPressEvent之前执行eventFilter。但是对我来说，重要的是，事件过滤器在父对象的KeyPressEvent之后触发。

我想要得到的结果如下:

Event of the parent object

Pressed any key

有什么方法可以定义执行顺序？

Answer 1

这是我想出的解决方案:

将mynewlineedit.cpp重命名为mynewlineedit.h，随处更改

并将eventwatcher.cpp更改为此:

#include <QWidget>
#include <QDebug>
#include <QKeyEvent>

#include <iostream>
#include <mynewlineedit.h>
class EventWatcher : public QObject
{
    QWidget* m_parent;
public:
   explicit EventWatcher(QWidget* parent = Q_NULLPTR) : QObject(parent), m_parent(parent)
   {
       if (parent)
       {
           parent->installEventFilter(this);
       }
   }

   virtual bool eventFilter(QObject*, QEvent* event) Q_DECL_OVERRIDE
   {
       if (event->type() == QEvent::KeyPress)
       {
           if(m_parent)
           {
               dynamic_cast<MyNewLineEdit*>(m_parent)->keyPressEvent(dynamic_cast<QKeyEvent*>(event));
           }
           std::cerr << "Pressed any key\n";
           return true;
       }

        return false;
   }
};