What's wrong with this information?

[Geng.Y]

I've checked this code for an hour and couldn't find anything wrong. Wish you can help me with this!

//annotation.h

#ifndef ANNOTATION_H
#define ANNOTATION_H

#include <QtWidgets/QMainWindow>
#include "ui_annotation.h"
#include "imagewidget.h"

class Annotation : public QMainWindow
{
	Q_OBJECT

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

	void Init();

private:
	Ui::AnnotationClass ui;

	QMenu *menu_file;
	QToolBar *toolbar_open;
	QToolBar *toolbar_save;
	QAction *action_open;
	QAction *action_save;

	ImageWidget *image_widget;

};

#endif // ANNOTATION_H

//annotation.cpp

#include "annotation.h"

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

	Init();
}

Annotation::~Annotation()
{

}

void Annotation::Init()
{
	menu_file = menuBar()->addMenu(tr("&File"));
	action_open = new QAction(tr("Open"),this);
	action_save = new QAction(tr("Save"),this);
	toolbar_open = addToolBar(tr("Open"));
	toolbar_save = addToolBar(tr("Save"));
	
	menu_file->addAction(action_open);
	menu_file->addAction(action_save);
	toolbar_open->addAction(action_open);
	toolbar_save->addAction(action_save);

	connect(action_open,&QAction::triggered,image_widget,&ImageWidget::Open);
	connect(action_save,&QAction::triggered,image_widget,&ImageWidget::Save);

	image_widget = new ImageWidget();
	setCentralWidget(image_widget);
}

//imagewidget.h

#ifndef IMAGEWIDGET_H
#define IMAGEWIDGET_H

#include <QWidget>
#include <QImage>
#include <QPainter>
#include <QFileDialog>
#include "ui_imagewidget.h"

class ImageWidget : public QWidget
{
	Q_OBJECT

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

public slots:
	void Open();
	void Save();
	void ReadXml();
	void paintEvent(QPaintEvent *);

private:
	Ui::ImageWidget ui;

	QImage *ptr_image;
};

#endif // IMAGEWIDGET_H

//imagewidget.cpp

#include "imagewidget.h"

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

	ptr_image = new QImage();
}

ImageWidget::~ImageWidget()
{

}

void ImageWidget::Open()
{
	QString fileName = QFileDialog::getOpenFileName(this,tr("Read Image"),".",tr("Image(*.bmp *.png *.jpg)"));

	if (!fileName.isEmpty())
	{
		ptr_image->load(fileName);
	}

	update();
}

void ImageWidget::Save()
{

}

void ImageWidget::ReadXml()
{

}

void ImageWidget::paintEvent(QPaintEvent *)
{
	QPainter painter(this);
	QRect image_rect(0,0,ptr_image->width(),ptr_image->height());

	painter.begin(this);
	painter.drawImage(image_rect,*ptr_image);

	update();

}

[taedium]

@Geng.Y said in What's wrong with this information?:

connect(action_open,&QAction::triggered,image_widget,&ImageWidget::Open);
connect(action_save,&QAction::triggered,image_widget,&ImageWidget::Save);

image_widget = new ImageWidget();

You are connecting to a dangling pointer here. Interchange image_widget definition and connect() calls.

[Geng.Y]

Thank you very much! I was so careless！

[taedium]

Also calling update() inside paintEvent will cause an infinte loop.