QVideoWidget的尺寸调整不佳

Question

I have a Qt application which simply captures from the default webcam and shows it on a QVideoWidget. In the ui, I have a simple MainWindow with a QGraphicsView inside a VerticalLayout:

ui design

My mainwindow.cpp=============================================

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    m_viewfinder = new QVideoWidget(ui->captureView);
    m_camera = new QCamera(QCameraInfo::defaultCamera());
    m_camera->setViewfinder(m_viewfinder);

    m_camera->start();
}

MainWindow::~MainWindow()
{
    m_camera->stop();
    delete m_viewfinder;
    delete m_camera;
    delete ui;
}

When I execute this, I get the application running, but the video contents do not scale according to the mainwindow size. Examples:

When I start the application

Resizing mainwindow down

Resizing mainwindow up

Is there some way to make the video content resize well and fit the available area? I have seen this answer: QVideoWidget: Video is cut off , but it doesn't offer any solution that works for me. When use the QGraphicsView-QGraphicsScene-QGraphicsVideoItem chain, I see nothing at all.

Answer 1

When you use the following instruction:

m_viewfinder = new QVideoWidget(ui->captureView);

You are setting as the parent of m_viewfinder to captureView , so the positions of m_viewfinder will be relative to captureView , but this does not indicate that it will be the same size as the parent.

One of the easiest ways to do this is to use a layout. Also, it is not necessary to create the QGraphicsWidget or the QVBoxLayout , so I recommend you to delete it and get the design as it was established by default:

and then we establish a layout that is placed in the centralWidget , and in this layout we add the QVideoWidget .

...
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    m_viewfinder = new QVideoWidget;
    QVBoxLayout *lay = new QVBoxLayout(ui->centralWidget);
    lay->addWidget(m_viewfinder);
    m_camera = new QCamera(QCameraInfo::defaultCamera());
    m_camera->setViewfinder(m_viewfinder);

    m_camera->start();
}
...

In the following link you can find the complete example.