关于c ++：如何在QScrollArea上绘制QImage？

How to draw QImage on QScrollArea? Did this, but have some minor problems QPainter::begin: Widget painting can only begin as a result of a paintEvent

好的，下面是我想要完成的：我想画出qimage，这样在图像太大的情况下窗口会有滚动条。首先，我有这样的东西：

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#include"imagewidget.h"
#include <QImage>
#include <QPainter>
#include <QGridLayout>
#include <QLabel>

ImageWidget::ImageWidget(QWidget* parent)
: QWidget(parent)
{
m_image = QImage();

scrollArea = new QScrollArea(this);

QGridLayout *gridLayout = new QGridLayout(this);
imgDisplayLabel = new QLabel(this);
imgDisplayLabel->setPixmap(QPixmap::fromImage(m_image));
imgDisplayLabel->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
imgDisplayLabel->setScaledContents(true);
imgDisplayLabel->adjustSize();

scrollArea->setWidget(imgDisplayLabel);

gridLayout->addWidget(scrollArea,0,0);
setLayout(gridLayout);

}

void ImageWidget::paintEvent(QPaintEvent* event)
{

QPainter paint(this);
if(!m_image.isNull())
paint.drawImage(0,0, m_image);

imgDisplayLabel->setPixmap(QPixmap::fromImage(m_image));
imgDisplayLabel->adjustSize();
imgDisplayLabel->setScaledContents(true);
}

void ImageWidget::setImage(QImage im)
{
m_image = im;
update();
}

void ImageWidget::removeImage()
{
m_image = QImage();
update();
}

但是，它并没有给我想要的效果：

enter image description here

当我把QPainter paint(this);改为QPainter paint(scrollArea);时，我收到了错误消息(或者，我猜是警告)：QPainter::begin: Widget painting can only begin as a result of a paintEvent但是我可以运行应用程序，打开/关闭图像。所以，这个程序实际上可以处理这个问题，但是这个错误消息让我很困扰，我想知道如何处理它。有了这一点，上面的SRC代码应用程序只有一行改变了，它可以正常工作并显示图像：

enter image description here