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Pushbutton crashed.



  • I'm a beginner, and I want button_clicked(). add and remove in lineEdit (). But the code I made is crashing.

    #include "test.h"  /  #include "ui_test.h"   /   #include "QMouseEvent"
    int value1= 0; int value2= 0; int value3= 0; int value4= 0;
    
    Test::Test(QWidget *parent) : QMainWindow(parent) , ui(new Ui::Test){
        ui->setupUi(this);
        ui->lineEdit1->setEnabled(false);
        ui->lineEdit2->setEnabled(false);
    
    }
    
    Test::~Test(){delete ui;}
    void Test::on_button1_clicked(){
        QMouseEvent *p= nullptr;
       if(p->button()==Qt::LeftButton){ui->lineEdit1->setText(QString::number(value1++));}
        else{if(p->button()==Qt::RightButton){ui->lineEdit1->setText(QString::number(value1--));}}
    }
    
    void Test::on_button2_clicked(){
        QMouseEvent *p= nullptr;
       if(p->button()==Qt::LeftButton){ui->lineEdit2->setText(QString::number(value2++));}
        else{if(p->button()==Qt::RightButton){ui->lineEdit2->setText(QString::number(value2--));}}
    }
    

    I tried to redeploy the tutorial code: https://forum.qt.io/topic/101957/check-if-button-was-right-clicked-or-left-clicked/11

    class CustomPushButton : public QPushButton{
        Q_OBJECT
    public:
        CustomPushButton(QWidget *parent = nullptr);
    
    protected:
       void	mousePressEvent(QMouseEvent *e) override;
       void mouseReleaseEvent(QMouseEvent *e) override;
    
    signals:
        void leftClicked();
        void rightClicked();
    };
    

    however I am confused if I connect leftclicked () with on_button1_clicked (); or if connect leftclicked()
    inside on_button1_clicked () that will check, where will send the value to lineEdit().
    This makes a simple check into a complex one in events... Can someone help me?


  • Lifetime Qt Champion

    @Gutks said in Pushbutton crashed.:

    QMouseEvent *p= nullptr;
    if(p->button()==Qt::LeftButton){ui->lineEdit1->setText(QString::number(value1++));}

    and you really expect that this will not crash? Dereferencing a nullptr will for sure not work - c++ basics.



  • @Christian-Ehrlicher Thanks for correcting, it worked here.

    Did not enter the block (if) and did not assign value in lineEdit(). Test using hitButton() to return pointer mouse, erro. ;--;

    QMouseEvent *e;
        if(hitButton(e->pos())==Qt::LeftButton){ui->lineEdit1->setText(QString::number(value1++));}}
    

    There is a way to check without using CONNECT()?
    How to CONNECT() would be like this?

    connect(ui->pushButton(),connect(leftClicked()),this,SLOT(mousePressEvent()));
    connect(ui->pushButton(),connect(rightClicked()),this,SLOT(mousePressEvent()));
    
    Object::connect No such signal Qpushbutton::rightClicked() 
    


  • @Gutks said in Pushbutton crashed.:

    connect(ui->pushButton(),connect(leftClicked()),this,SLOT(mousePressEvent()));

    This cant work either.

    What is ui->pushButton() in your case? () indicates a function... Does it return your unique instance of your CustomPushButton class? I dont think so :)

    2nd param must be SIGNAL(leftClicked()).
    In addition, I dont think that mousePressEvent is a slot, you can connect to.

    Edit:

    Where do you create the instances of your Pushbutton class? Would be helpful if you show your test.cpp and CustomPushButton.cpp

    Edit_2:

    Your signal definitions in your button class are correct. Now you need to emit them in your pushButton's mouseClickEvent/ mouseReleaseEvent (according to you logic). Inside your implementation of these two, you put your check, which mouse key was actually used. THEN you emit the corresponding signal.

    Inside your test widget class, where your pushButtons are placed, you make the standard connection to setup what will happen, if your button is clicked with left or right mouse key... (Two different slots for your actions)

    Something like:
    connect(pushbutton1, SIGNAL(leftClicked()), this, SLOT (btnLeftClicked()));

    And this slot is the place, where you put your code to increase your counter (lineEdit) or do something else.

    Edit_3:

    Are your value vars global variables? Better put them in your test header as member vars.



  • @Pl45m4 said in Pushbutton crashed.:

    Thanks for responding and sorry for the delay.

    Pl45m4: "What is ui->pushButton() in your case?" - And I typed it wrong, thanks for correcting. ui->pushButton1.

    CustomPushButton.cpp, I tried to use macro const Q_Q(QAbstractButton),
    error: use of undeclared identifier 'q_func'.

    Not being able to access the emitPressed() and emitRelease(), class scope QAbstractButton.

    So my mousePressEvent and mouseReleaseEvent, stayed like this:
    customushbutton.cpp

    #include "custompushbutton.h"
    
    CustomPushButton::CustomPushButton(QWidget *parent){}
    void CustomPushButton::mousePressEvent(QMouseEvent *e){
        QAbstractButton *p;
        if(e->button()==Qt::LeftButton){p->click();emit pressed();}
        else{if(e->button()==Qt::RightButton){p->click();emit pressed();}else{e->ignore();return;}}
    }
    
    void CustomPushButton::mouseReleaseEvent(QMouseEvent *e){
        QAbstractButton *p;
        //Q_Q(QAbstractButton);
        if(e->button()==Qt::LeftButton){p->click();emit pressed();}
        else{if(e->button()==Qt::RightButton){p->click();emit pressed();}else{e->ignore();return;}}
    }
    

    test.cpp

    #include "test.h"
    #include "ui_test.h"
    #include "QMouseEvent"
    
    int value1= 0;
    int value2= 0;
    int value3= 0;
    int value4= 0;
    
    Test::Test(QWidget *parent) : QMainWindow(parent) , ui(new Ui::Test){
        ui->setupUi(this);
        ui->lineEdit1->setEnabled(false);
        ui->lineEdit2->setEnabled(false);
    
        connect(ui->button1, SIGNAL(leftClicked()) , this, SLOT(btnLeftClicked()))   ;
        connect(ui->button1, SIGNAL(rightClicked()), this, SLOT (btnRightClecked())) ;
    
        connect(ui->button2, SIGNAL(leftClicked()) , this, SLOT(btnLeftClicked()))   ;
        connect(ui->button2, SIGNAL(rightClicked()), this, SLOT(btnRightClicked()))  ;
    }
    

    QObject::connect: No such signal QPushButton::leftClicked()
    The connect and increment should be inside the on_button_clicked()?

    Yes, I put it as global, to facilitate the test. If I did it as a member of the class (seters and geters),

    I would have work to get the value of the line edit and convert string to number, and so do the increment
    and decrement.



  • @Gutks said in Pushbutton crashed.:

    Not being able to access the emitPressed() and emitRelease(), class scope QAbstractButton.

    Why not? Your own pushbutton class inherits QPushbutton and you have added some signals on your own... Just emit these.
    (emit pressed() is the wrong signal after all. You named you signals in your button class differenta and these are the ones, you need to use inside your mouse event)

    And again my question :)
    Where do you create (new) your button instances button1 and button2?
    ui->button1 only works, if you've created your button with QtDesigner (or if they are part of your ui_classname.h at least).

    Edit:

    Do you make use of widget promotion? If yes, it may work like this, but if you don't, you'll need to instantiate your buttons first, in order to connect something to them.

    @Gutks said in Pushbutton crashed.:

    QObject::connect: No such signal QPushButton::leftClicked()

    This indicates, that your ui->button1 is currently not your custom button. I would say, these are still pointers to your basic QPushButtons.
    Read about "Promoting Widgets in Qt" (Link) or create your CustomPushbuttons by code and add them to you layout manually.

    Your QAbstractButton *p inside your mouseEvents also does nothing and is not necessary. What do you expect from doing this? :)

    @Gutks said in Pushbutton crashed.:

    I would have work to get the value of the line edit and convert string to number, and so do the increment
    and decrement.

    No, you dont. Only if you want to access these values from "outside". If you use them only their own class, you dont need getter / setter. In addition, you could make use of signals & slots to change the values, but if these are just counters, you dont even need to do that.



  • @Pl45m4

    NameProjet= Test;
    classe1= customPushButton.h ; customPushButton;
    Classe2= test.h ; test.cpp = ( Widget, ui->classe)
    other= main.cpp;

    I tried to use this logic similar to the previous tutorial, however, Macro ( Q_Q() ),
    it is not stated, when I try to instantiate q->emitPressed(). return error: use of undeclared identifier 'q_func';

    I tried to change the 'Q' for 'D' ( Q_D), equal to the situation below, returns another.
    error: cannot initialize a variable of type 'QAbstractButtonPrivate *const' with an rvalue of type 'QPushButtonPrivate'
    Q_D(Class)

    void QAbstractButton::mousePressEvent(QMouseEvent *e){
        Q_D(QAbstractButton);
        if (e->button() != Qt::LeftButton) {
            e->ignore();
            return;
        }
        if (hitButton(e->pos())) {
            setDown(true);
            d->pressed = true;
            repaint();
            d->emitPressed();
            e->accept();
        } else {
            e->ignore();
        }
    }
    

    Ok, I'm going to make the right sign and study the custom widgets with Qt Designer. Thank you for the patience, using google translation . I return with possible results or errors.



  • @Gutks
    Especially if you are a beginner, why are you trying to use macros like Q_D() and Q_Q() at all? So far as I know they are for internal Qt code. I have never used them in any user code I have written, why do you think you need them?



  • @JonB In order to instantiate: emitPressed(); emitRelease(); equal example
    of the QAbstractButton class.



  • @Gutks said in Pushbutton crashed.:

    instantiate: emitPressed(); emitRelease();

    Mmm, strange that you need to "instantiate" what seems to be signals...



  • @Gutks
    Yes, but why are you doing so, given that emitPressed() is not documented and private to the innards of QAbstractButton? Which is why you are running into the compilation errors.... My question is: why are trying to do anything like this? The fact that it's in QAbstractButtonPrivate should give you a clue.



  • @JonB

    The implementation of this function is accessing Q_D, since I am re-implementing it, I thought I could do the same.

    void QAbstractButton::mousePressEvent(QMouseEvent *e)
    

    I will study the qt designer, to try to solve, otherwise, I will create an Auxiliary button to remove in the edit line. I think it's simpler than using events



  • @Gutks
    But why are you "re-implementing" it at all? Usually a user class sub-classes, not re-implements. Re-implementing is fraught, e.g. what happens if the internals change over time. Since you say "I'm a beginner" I cannot see why you would want to do such a thing, when 99.9% of other users do not.

    I keep saying the same thing, so I'll leave it to you now.



  • @JonB
    Okay, thanks for trying to help. I will search for a solution to my problem.



  • @Gutks

    I already gave you an almost step by step manual how to solve your problem... You dont need Q_Q or reimplement any signals.



  • @Gutks
    Both @Pl45m4 & I are trying to say you don't need to go down the route you are on....



  • @Gutks said in Pushbutton crashed.:

    if(p->button()==Qt::LeftButton){ui->lineEdit1->setText(QString::number(value1++));}
    
    else{if(p->button()==Qt::RightButton){ui->lineEdit1->setText(QString::number(value1--));}
    

    From your requirements it's apparent you need a custom QPushButton that extends existing one by adding just the rightclicked() signal, and nothing else. So you'll have both signals (existing left click) and new one (right click) to connect as you wish.

    Please take a look at this SO question & answers.



  • @Gutks
    If what @Pablo-J-Rogina has discerned is correct --- you just want a left-/right-click to increment/decrement a number in a QLineEdit, is that right? --- then you would be better just using a QSpinBox, which is for entering numbers, and you wouldn't have any of this.....



  • @JonB said in Pushbutton crashed.:

    then you would be better just using a QSpinBox,

    I think the goal here is the rightclicked() signal, what you connect that to is not relevant at this point



  • @Pablo-J-Rogina
    Oh, I see. You may be right. Or it just might turn out the user was going to use a left-/-right-click on a button to inc/dec a number, you never know... :)

    On a different tone, it's "unusual" to have the user right-click on a button. Possible, but possibly not intuitive. A "rocker" pushbutton (click at left/right for different behaviour, but with left mouse) might be another possibility.



  • @Gutks

    Button.h

    #ifndef LR_CLICKBUTTON_H
    #define LR_CLICKBUTTON_H
    
    #include <QPushButton>
    
    class LR_ClickButton: public QPushButton
    {
        Q_OBJECT
    public:
    
        LR_ClickButton(QWidget *parent = nullptr);
    
    
    protected:
       void	mousePressEvent(QMouseEvent *e) override;
       void mouseReleaseEvent(QMouseEvent *e) override;
    
    signals:
        // Not needed, since one signal which sends MouseEvent to get handled in slot
        //void leftClicked();
        //void rightClicked();
    
        void myClicked(QMouseEvent *e);
    };
    
    #endif // LR_CLICKBUTTON_H
    

    Button.cpp

    #include "lr_clickbutton.h"
    #include <QMouseEvent>
    #include <QDebug>
    LR_ClickButton::LR_ClickButton(QWidget *parent):
        QPushButton(parent)
    {
    
    }
    
    void LR_ClickButton::mousePressEvent(QMouseEvent *e)
    {
        QPushButton::mousePressEvent(e);
    }
    
    void LR_ClickButton::mouseReleaseEvent(QMouseEvent *e)
    {
        if(e->button() == Qt::LeftButton)
        {
            qDebug() << "Left";
            emit myClicked(e);
        }
        else if (e->button() == Qt::RightButton) {
    
            qDebug() << "Right";
            emit myClicked(e);
    
        }
            QPushButton::mouseReleaseEvent(e);
    }
    

    MainWindow.h

    public slots:
        void myButtonClicked(QMouseEvent *e);
    

    MainWindow.cpp

    // #########  C'TOR  #####################
        LR_ClickButton *button1 = new LR_ClickButton(this);
    
        centralWidget()->layout()->addWidget(button1);
    
        connect(button1, &LR_ClickButton::myClicked, this, &MainWindow::myButtonClicked);
    
    // ######################################
    
    
    void MainWindow::myButtonClicked(QMouseEvent *e)
    {
        if(e->button() == Qt::LeftButton)
        {
            // Of course you can put anything you want here
            int val = ui->spinBox->value();
            ui->spinBox->setValue(val + 1);
        }
        else if (e->button() == Qt::RightButton) {
    
            // or here
            int val = ui->spinBox->value();
            ui->spinBox->setValue(val - 1);
        }
    }
    
    
    

    Wasn't that hard, right? :)

    Result:

    3 left-clicks increase value by 3.
    Bildschirmfoto vom 2020-08-19 15-13-02.png

    2 right-clicks decrease value by 2 again.
    Bildschirmfoto vom 2020-08-19 15-13-33.png



  • @JonB said in Pushbutton crashed.:

    On a different tone, it's "unusual" to have the user right-click on a button. Possible, but possibly not intuitive

    Might not be the most intuitive solution but this is actually used a lot in games (with a hint to this behavior ofc)



  • @Pl45m4
    Point taken! Not in any of the games I play that I can think of, though most of mine are 2D turn-based from the last millennium... ;-)



  • @Christian-Ehrlicher @Pl45m4 @JonB @Pablo-J-Rogina

    Thank you very much, you don't know how it helped me. Otherwise, I would have to create an internal storage system for each button between the tabs and remove it when editing the line.

    Yes, and a tool I am creating to help the 1 game community. How does it activate as resolved?
    Captura de tela de 2020-08-19 08-05-11.png



  • @Gutks said in Pushbutton crashed.:

    How does it activate as resolved

    Either at bottom of page Topic Tools button, or if you feel a particular post answered it the vertical ... button at the right on that post.



  • @JonB

    This is exactly what I was expecting and what I thought of.... These type of games, where you have ingame shops and a lot of inventories... If you left-click an item, you probably buy it from shop or use it, if you right-click, you drop it or sell it :)


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