Whats' wrong with this "connect“ ？

[Geng.Y]

I wanna connect several signals with several slots, but why the first "connect" works while the second one doesn't? Wish you can help me with this!

//minidraw.h

#ifndef MINIDRAW_H
#define MINIDRAW_H

#include <QtWidgets/QMainWindow>
#include "ui_minidraw.h"
#include "viewwidget.h"
#include <QMessageBox>

class MiniDraw : public QMainWindow
{
	Q_OBJECT

public:
	MiniDraw(QWidget *parent = 0);
	~MiniDraw();

	void Init();
	void About();
private:
	Ui::MiniDrawClass ui;

	QMenu *pMenu1,*pMenu2;
	QAction *pAction0,*pAction1,*pAction2,*pAction3,*pAction4,*pAction5,*pAction6;
	QToolBar *pToolbar1,*pToolbar2,*pToolbar3,*pToolbar4,*pToolbar5,*pToolbar6;

	ViewWidget *view_widget_;
	
};

#endif // MINIDRAW_H

//minidraw.cpp

#include "minidraw.h"


MiniDraw::MiniDraw(QWidget *parent)
	: QMainWindow(parent)
{
	ui.setupUi(this);

	Init();

}

MiniDraw::~MiniDraw()
{

}

void MiniDraw::Init()
{
	pMenu1 = menuBar()->addMenu(tr("&Menu"));
	pMenu2 = menuBar()->addMenu((tr("&About")));

	pAction0 = new QAction(tr("&About"),this);
	pAction1 = new QAction(tr("&Line"),this);
	pAction2 = new QAction(tr("&Rectangle"),this);
	pAction3 = new QAction(tr("Ellipse"),this);
	
	pToolbar1 = addToolBar(tr("&Line"));
	pToolbar2 = addToolBar(tr("&Rectangle"));
	pToolbar3 = addToolBar(tr("&Ellipse"));

	pToolbar1->addAction(pAction1);
	pToolbar2->addAction(pAction2);
	pToolbar3->addAction(pAction3);

	pMenu1->addAction(pAction1);
	pMenu1->addAction(pAction2);
	pMenu1->addAction(pAction3);
	pMenu2->addAction(pAction0);
	
	connect(pAction0,&QAction::triggered,this,&MiniDraw::About);
	connect(pAction1,&QAction::triggered,this,&ViewWidget::setType_Line); // **It dosen't work!!!**
	view_widget_ = new ViewWidget();
	setCentralWidget(view_widget_);
}

void MiniDraw::About()
{
	QMessageBox::about(this,tr("About"),tr("Demo of MiniDraw\n  by Geng.Y"));
}

//viewwidget.h

#ifndef VIEWWIDGET_H
#define VIEWWIDGET_H

#include <QWidget>
#include <QMouseEvent>
#include <QPainter>
#include <vector>
#include "ui_viewwidget.h"
#include "Figure.h"

using namespace std;

enum FigureType
{
	kDefault = 0,
	kLine = 1,
	kEllipse = 2,
};

class ViewWidget : public QWidget
{
	Q_OBJECT

public:
	ViewWidget(QWidget *parent = 0);
	~ViewWidget();

	void mousePressEvent(QMouseEvent *event);
	void mouseMoveEvent(QMouseEvent * event);
	void mouseReleaseEvent(QMouseEvent* event);
	void paintEvent(QPaintEvent *);

	void setType_Line();
	void setType_Ellipse();

private:
	Ui::ViewWidget ui;

	bool draw_status;
	QPoint mStartpoint;
	QPoint mEndPoint;

	vector<Figure*> figure_array;
	FigureType figure_type;
	
};

#endif // VIEWWIDGET_H

//viewwidget.cpp

#include "viewwidget.h"

ViewWidget::ViewWidget(QWidget *parent)
	: QWidget(parent)
{
	ui.setupUi(this);

	draw_status = false;
}

ViewWidget::~ViewWidget()
{
	for (int i=0;i<figure_array.size();i++)
	{
		if (figure_array[i])
		{
			delete figure_array[i];
			figure_array[i] = NULL;
		}
	}
}

void ViewWidget::mousePressEvent(QMouseEvent *event)
{
	if (Qt::LeftButton==event->button())
	{
		draw_status = true;

		mStartpoint = mEndPoint = event->pos();
	}
}

void ViewWidget::mouseMoveEvent(QMouseEvent * event)
{
	if (draw_status)
	{
		mEndPoint = event->pos();
	}
}

void ViewWidget::mouseReleaseEvent(QMouseEvent *evnet)
{
	draw_status = false;
}

void ViewWidget::paintEvent(QPaintEvent *)
{
	QPainter painter(this);
	painter.begin(this);
	//painter.drawLine(mStartpoint,mEndPoint);
	//painter.drawEllipse(mStartpoint.rx(),mStartpoint.ry(),mEndPoint.rx()-mStartpoint.ry(),mEndPoint.ry()-mStartpoint.ry());
	painter.end();

	update();
}

void ViewWidget::setType_Line()
{
	figure_type = kLine;
}

void ViewWidget::setType_Ellipse()
{
	figure_type = kEllipse;
}

[Vinod Kuntoji]

@Geng-Y ,

You should create the ViewWidget object before the connect statement,

view_widget_ = new ViewWidget();
connect(pAction0,&QAction::triggered,this,&MiniDraw::About);
connect(pAction1,&QAction::triggered,view_widget_,&ViewWidget::setType_Line);

[Geng.Y]

Thank you very much!

[Vinod Kuntoji]

@Geng.Y

Hi,

Please mark your issue as solved.