Painter在继承的QOpenGLWidget类上未激活

如何解决Painter在继承的QOpenGLWidget类上未激活

我想在Qt中非常有效地绘制基本的2D形状（正方形），因此我继承了 QOpenGLWidget ，如下所示：

WatorOpenGLWidget.hpp

#include <QOpenGLWidget>
#include <QPainter>
#include "Environment.hpp"

#ifndef WATOROPENGLWIDGET_HPP
#define WATOROPENGLWIDGET_HPP


class WatorOpenGLWidget : public QOpenGLWidget
{
private:
    Environment* environment;
public:
    WatorOpenGLWidget(QWidget* widget,Environment* environment);
    void initializeGL() override;
    void paintGL() override;
    void resizeGL(int w,int h) override;
    void setEnvironment(Environment *e) {this->environment = e;};
};

#endif // WATOROPENGLWIDGET_HPP

WatorOpenGLWidget.cpp

#include "WatorOpenGLWidget.hpp"
#include <iostream>

WatorOpenGLWidget::WatorOpenGLWidget(QWidget* widget,Environment* e): QOpenGLWidget(widget),environment(e){
}
void WatorOpenGLWidget::initializeGL() {
    glClearColor(0,1);
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_LIGHT0);
    glEnable(GL_LIGHTING);
    glColorMaterial(GL_FRONT_AND_BACK,GL_AMBIENT_AND_DIFFUSE);
    glEnable(GL_COLOR_MATERIAL);
}

void WatorOpenGLWidget::paintGL(){
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    QPainter painter(this);
    painter.setBrush(QBrush(Qt::blue));
    painter.drawRect(0,3 * environment->getWidth(),3 * environment->getHeight());

    std::vector<Agent*> agents = environment->getAgents();
    for(uint32_t i = 0; i < agents.size(); i++){
        painter.setBrush(agents[i]->getColor());
        painter.drawRect(agents[i]->getX() * 3,agents[i]->getY() * 3,3,3);
    }
}

void WatorOpenGLWidget::resizeGL(int w,int h){
    glViewport(0,w,h);
}

然后从mainwindow类创建我的自定义窗口小部件 WatorOpenGLWidget ：

#include "Mainwindow.hpp"
#include "ui_mainwindow.h"
#include "Environment.hpp"
#include "Fish.hpp"
#include "Shark.hpp"
#include <iostream>

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

    timer = new QTimer(this);
    connect(timer,SIGNAL(timeout()),this,SLOT(updateEnvironment()));
    timer->start(20);
    tick = 0;

    initializeEnvironment();
    opengl_widget = new WatorOpenGLWidget(nullptr,environment);
    opengl_widget->setFixedSize(3 * environment->getWidth(),3 * environment->getHeight());
    ui->scrollAreaWidgetContents->layout()->addWidget(opengl_widget);
    updateGUI();
}

void MainWindow::initializeEnvironment(){
    this->environment = new Environment(100,100,0);

    std::vector<Agent*> agents;
    for(uint32_t i = 0; i < 5000; i++){
        agents.push_back(new Fish());
    }

    for(uint32_t i = 0; i < 1000; i++){
        agents.push_back(new Shark());
    }

    this->environment->placeAgents(agents);
}

void MainWindow::updateEnvironment(){
    initializeEnvironment();
    std::vector<Agent*> agents = environment->getAgents();
    for(uint32_t i = 0; i < agents.size(); i++){
        agents[i]->decide();
    }

    updateGUI();
}

void MainWindow::updateGUI(){
    opengl_widget->setEnvironment(environment);
    opengl_widget->paintGL();
    tick++;
    std::string tick_text = "tick " + std::to_string(tick);
    ui->tickLabel->setText(QString::fromStdString(tick_text));
}

MainWindow::~MainWindow()
{
    delete timer;
    delete environment;
    delete ui;
}

每次计时器触发图形时，该图形都工作良好，但是在运行时会生成以下输出：

QPainter::begin: Paint device returned engine == 0,type: 1
QPainter::setBrush: Painter not active
QPainter::drawRects: Painter not active
QPainter::setBrush: Painter not active
QPainter::drawRects: Painter not active
QPainter::setBrush: Painter not active
QPainter::drawRects: Painter not active

我应该怎么做才能防止这种情况？另外，使用QPainter对象比使用OpenGL本机函数消耗更多的CPU吗？

解决方法

您不应直接调用paintGL()，而应调用update()方法，该方法将调用paintEvent()方法，而这又将调用paintGL()。

void MainWindow::updateGUI(){
    opengl_widget->setEnvironment(environment);
    opengl_widget->update();
    tick++;
    ui->tickLabel->setText(QString("tick %1").arg(tick));
}