Question

我从另一个类（带有实例）访问ui元素时遇到问题。我的应用程序中有第二个QMainWindow，我可以在secondWindow.cxx类中访问所有ui元素，但不能访问read.cxx类。我的代码如下所示。我的错误在哪里？谢谢你的帮助。

-------------------------------secondWindow.h------------------------------------

#ifndef __secondWindow_h
#define __secondWindow_h

#include "ui_secondwindow.h"

class secondWindow : public QMainWindow
{
    friend class read;
    igstkStandardClassBasicTraitsMacro(secondWindow, QMainWindow);
    Q_OBJECT

public:
    igstkStateMachineMacro();

    secondWindow();
    virtual ~secondWindow();
    void createSignalAndSlots();

public slots:
    void secondWindowTest();

protected:

private:
    Ui::secondMainWindow m_secondWindowUI;
};
#endif

-------------------------------secondWindow.cxx------------------------------------

#include "secondWindow.moc"
#include "secondWindow.h"
#include "read.h"

secondWindow::secondWindow() :m_StateMachine(this)
{
    m_secondWindowUI.setupUi(this);
    createSignalAndSlots();
}

void secondWindow::createSignalAndSlots()
{
    connect(m_secondWindowUI.pushButton1, SIGNAL(clicked()),this, SLOT(secondWindowTest()));

    connect(m_secondWindowUI.pushButton2, SIGNAL(clicked()), read::instance(), SLOT(readTest()));
}

void secondWindow::secondWindowTest()
{
    m_secondWindowUI.pushButton1->setEnabled(true); //OK
}

secondWindow::~secondWindow(){}


---------------------------------read.h--------------------------------------

#pragma once

#include "secondWindow.h"

class read : public QObject
{
    Q_OBJECT

public:
    static read *instance();
    read();
    virtual ~read() {}

public slots:
    void readTest();

protected:
    secondWindow    *m_readUI;
    static read     *m_read;

private:
};

---------------------------------read.cxx--------------------------------------
#include <read.moc>
#include "secondWindow.h"
#include "read.h"

read *read::m_read= NULL;

read::read()
{
    m_readUI = dynamic_cast<secondWindow*>( QApplication::instance() );
}

read *read::instance()
{
    if(m_read == NULL)
    m_read = new read();

    return m_read;
}

void read::readTest()
{
    m_readUI->m_secondWindowUI.qlabelTest->setText("test"); //segmentation fault
}

Answer 1

您正在投射QApplication::instance()，这是源自QApplication * QCoreApplication *的{{1}} QObject *。这不起作用，它不是secondWindow *，甚至不是QMainWindow *，甚至不是QWidget *。

除此之外，您的编码风格相当奇怪 - 在Qt中，习惯使用CamelCase用于类，而不是thisStuff通常适用于函数和方法。包括<read.moc>是错误的。为什么read::m_read是静态的？最后，两个窗口类之间的耦合是以一种奇怪的方式建立的（访问像QApplication这样的全局内容只是为了获得对另一个窗口的引用，这些代码都是丑陋的代码）。一种更好，更明显的方法是将所有窗口包装在父对象中或明确设置依赖关系，可能是这样的：

MainWindow *mainWindow = new MainWindow();
SecondWindow *second = new SecondWindow(mainWindow);
UtilityWindow *utilityWin = new UtilityWindow(second);

从另一个类c ++访问UI元素

1 个答案: