信号和插槽以及向主窗口发出信号答案

【问题标题】：Signal and Slot and emitting signal to mainwindow信号和插槽以及向主窗口发出信号
【发布时间】：2022-08-03 16:35:29
【问题描述】：

鼠标类在新线程中创建进程并运行evtest命令监听我的鼠标按钮按下。当我按下按钮时，鼠标类中的 ButtonReceived 逐行接收进程的输出。我添加了一些我得到的输出作为评论。现在我正在尝试根据输出向主窗口类发出信号。在主窗口类构造函数中，我创建了一个鼠标类并将其信号连接到我的 ButtonReceived 插槽，但它从不触发。我究竟做错了什么？

主文件

#include \"mainwindow.h\"

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;

    w.show();
    return a.exec();
}

主窗口.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QMessageBox>
#include <QObject>
#include \"mouse.h\"

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
    Mouse *m;
private slots:
    void ButtonReceived(const QString &);

};

#endif // MAINWINDOW_H

主窗口.cpp

#include \"mainwindow.h\"
#include \"./ui_mainwindow.h\"
#include \"mouse.h\"

MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow)
{

    qDebug() << \"MainWindow created\";
    ui->setupUi(this);

    m = new Mouse;     // new Mouse class then connect its signal to this class\'s slot but it\'s not working
    bool ctn = connect(p,SIGNAL(readyReadStandardOutput()),this,SLOT(ButtonPressed()));
    qDebug() << ctn;  //true

}
MainWindow::~MainWindow()
{
    qDebug() << \"MainWindow destroyed\";
    delete m;
    delete ui;
}

void MainWindow::ButtonReceived(const QString &btn)
{
   qDebug() << \"ButtonReceived\";
}

鼠标.h

#ifndef MOUSE_H
#define MOUSE_H

#include <QObject>
#include <QProcess>

using namespace std;

class Mouse : public QObject
{
    Q_OBJECT

public:
    explicit Mouse(QObject *parent = nullptr);
    ~Mouse();

private:
    QProcess *p;
    QThread *t;

private slots:
    void ButtonPressed();   // when evtest has output


signals:
    void ButtonPressedSignal(const QString&);


};

#endif // MOUSE_H

鼠标.cpp

#include \"mouse.h\"
#include <QDebug>
#include <QThread>

Mouse::Mouse(QObject *parent) : QObject{parent}
{
    t = new QThread;           // new Thread
    p = new QProcess();        // new Process
    p->moveToThread(t);        // run Process on Thread

    // connect process output to slot ButtonPressed
    connect(p,SIGNAL(readyReadStandardOutput()),this,SLOT(ButtonPressed()));

    // run evtest with mouse\'s device ID
    // TODO: find mouse ID with mouse name since ID can change
    p->startCommand(\"sudo evtest /dev/input/event24\");
    p->waitForFinished(-1);
    t->start();
}

Mouse::~Mouse()
{
    delete p;
    delete t;
}


void Mouse::ButtonPressed()
{
    QString out = p->readAllStandardOutput();
    if (out.indexOf(\"EV_KEY\") > 0 && out.indexOf(\"value 1\") > 0)
    {
        qDebug() << out;
/*
* Here I get output from the process like
\"Event: time 1658273579.607487, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90001\\nEvent: time 1658273579.607487, type 1 (EV_KEY), code 272 (BTN_LEFT), value 1\\n\"
\"Event: time 1658273581.285479, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90002\\nEvent: time 1658273581.285479, type 1 (EV_KEY), code 273 (BTN_RIGHT), value 1\\nEvent: time 1658273581.285479, -------------- SYN_REPORT ------------\\n\"
\"Event: time 1658273585.465477, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90003\\nEvent: time 1658273585.465477, type 1 (EV_KEY), code 274 (BTN_MIDDLE), value 1\\nEvent: time 1658273585.465477, -------------- SYN_REPORT ------------\\n\"
\"Event: time 1658273587.670479, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90004\\nEvent: time 1658273587.670479, type 1 (EV_KEY), code 275 (BTN_SIDE), value 1\\nEvent: time 1658273587.670479, -------------- SYN_REPORT ------------\\n\"
\"Event: time 1658273588.404471, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90005\\nEvent: time 1658273588.404471, type 1 (EV_KEY), code 276 (BTN_EXTRA), value 1\\nEvent: time 1658273588.404471, -------------- SYN_REPORT ------------\\n\"
\"Event: time 1658273591.211491, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90006\\nEvent: time 1658273591.211491, type 1 (EV_KEY), code 277 (BTN_FORWARD), value 1\\nEvent: time 1658273591.211491, -------------- SYN_REPORT ------------\\n\"
\"Event: time 1658273591.852480, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90007\\nEvent: time 1658273591.852480, type 1 (EV_KEY), code 278 (BTN_BACK), value 1\\nEvent: time 1658273591.852480, -------------- SYN_REPORT ------------\\n\"
\"Event: time 1658273593.851492, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90009\\nEvent: time 1658273593.851492, type 1 (EV_KEY), code 280 (?), value 1\\nEvent: time 1658273593.851492, -------------- SYN_REPORT ------------\\n\"
\"Event: time 1658273594.704493, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90008\\nEvent: time 1658273594.704493, type 1 (EV_KEY), code 279 (BTN_TASK), value 1\\nEvent: time 1658273594.704493, -------------- SYN_REPORT ------------\\n\"



so that works
now I want to emit a signal to my mainwindow



*/
        if (out.indexOf(\"BTN_LEFT\") > 0)
            emit ButtonPressedSignal(\"Left\");
        if (out.indexOf(\"BTN_RIGHT\") > 0)
            emit ButtonPressedSignal(\"Right\");
        if (out.indexOf(\"BTN_EXTRA\") > 0)
            emit ButtonPressedSignal(\"G4\");
        if (out.indexOf(\"BTN_SIDE\") > 0)
            emit ButtonPressedSignal(\"G3\");
        if (out.indexOf(\"BTN_BACK\") > 0)
            emit ButtonPressedSignal(\"G6\");
        if (out.indexOf(\"BTN_FORWARD\") > 0)
            emit ButtonPressedSignal(\"G5\");
        if (out.indexOf(\"BTN_TASK\") > 0)
            emit ButtonPressedSignal(\"G7\");
        if (out.indexOf(\"?\") > 0)
            emit ButtonPressedSignal(\"G8\");
        if (out.indexOf(\"BTN_MIDDLE\") > 0)
            emit ButtonPressedSignal(\"Middle\");
    }
}

CM-1207 我不知道为什么它说 p 但它在我的源代码中说 m ，但我把它改成了你所拥有的

我之前试过这个，但是在连接参数中添加了 const 和 & 但我得到了这个错误

变化

在 mainwindow.cpp

MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow)
{

    qDebug() << \"MainWindow created\";
    ui->setupUi(this);

    m = new Mouse;
    bool ctn = connect(m,SIGNAL(ButtonPressedSignal(const QString&)),this,SLOT(ButtonReceived(const QString&)));
    qDebug() << \"MainWindow connection: \" << ctn;

}

在鼠标.cpp

Mouse::Mouse(QObject *parent) : QObject{parent}
{
    t = new QThread;           // new Thread
    p = new QProcess();        // new Process
    p->moveToThread(t);        // run Process on Thread

    // connect process output to slot ButtonPressed
    bool ctn = connect(p,SIGNAL(readyReadStandardOutput()),this,SLOT(ButtonPressed()));
    qDebug() << \"Mouse connection: \" << ctn;

    // run evtest with mouse\'s device ID
    // TODO: find mouse ID with mouse name since ID can change
    p->startCommand(\"sudo evtest /dev/input/event24\");
    p->waitForFinished(-1);
    t->start();
}

我认为我的错误出在鼠标类中，但我不确定如何解决。我永远有 p->waitForFinished ，因为每次我永远按下按钮或直到我终止它时，进程都会运行并输出。这对我来说似乎是必要的，因为没有 p->waitForFinished 永远 QProcess 会超时并死掉。但是，这会阻塞主窗口。我将 QProcess 放在一个线程中，认为它会永远异步运行，但它仍然会阻止 mainwindow 甚至显示。

标签： c++ qt

【解决方案1】：

这个项目可以编译吗？数据成员p 在Mouse 类中被声明为私有，但是如何在MainWindow 类中访问它并且没有Mouse 对象呢？

我认为这段代码会帮助你：

MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new ui::MainWindow)
{
    ...
    m = new Mouse;
    bool ctn = connect(m, SIGNAL(ButtonPressedSignal(const QString&)), this, SLOT(ButtonReceived(const QString&)));
    ... 
}

在这里，如果由*m.p 管理的进程的标准输出可用，由于在Mouse 构造函数中完成的连接Mouse::ButtonPressed 插槽被调用为m，如果其逻辑合适，它会发出Mouse::ButtonPressedSignal。由于在上面的构造函数代码中，此信号连接到构造 MainWindow 的 MainWindow::ButtonReceived 插槽，因此按预期调用此插槽。

【讨论】：

m=新鼠标；（）不见了？没有编译器错误？
不，没有。甚至没有注意到。谢谢