Question

我想在Qt（Qt 5.9.0- MinGW 32位）画一条线，但只是页面是蓝色的。这个程序运行较旧的QT。我试图改变我的程序，但它没有用。

当我将Qt + = opengl添加到专业文件Qt显示错误并最终将库添加到专业文件时。

QT       += core gui
QT += opengl

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = DrawLine
TEMPLATE = app


SOURCES += main.cpp\
        mainwindow.cpp \
    glwidget.cpp

HEADERS  += mainwindow.h \
    glwidget.h

FORMS    += mainwindow.ui
LIBS += -lopengl32

函数opengl的类窗口小部件。

#ifndef GLWIDGET_H
#define GLWIDGET_H

#include <QtWidgets>
#include <QGLWidget>  //QT  +=  opengl
#include <QOpenGLFunctions>  //QT  +=  gui


class GLWidget : public QGLWidget, protected QOpenGLFunctions
{
    Q_OBJECT

public:
    explicit GLWidget(QWidget *parent = 0, QGLWidget *shareWidget = 0);
    ~GLWidget();

protected:
    void initializeGL()override;
    void paintGL()override;
    void resizeGL(int width, int height)override;

    void keyPressEvent(QKeyEvent *e);

private:
    int sample;
};

我写了这段代码，但只有蓝屏没有出现。

#include "glwidget.h"

GLWidget::GLWidget(QWidget *parent, QGLWidget *shareWidget)
    : QGLWidget(parent, shareWidget)
{
    sample = 0;
}

GLWidget::~GLWidget()
{
}

void GLWidget::initializeGL()
{
    initializeOpenGLFunctions();
//    glClearColor(0.0, 0.0, 102.0/255.0, 0.0);
//          glMatrixMode(GL_PROJECTION);
//          glLoadIdentity();
//          glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
}

void GLWidget::paintGL()
{

   glClearColor(0.1,0.6,0.7,1);
    glClear(GL_COLOR_BUFFER_BIT);
  //  glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    switch (sample)
    {
    case 0:
        glColor3f(0.1, 0.1, 0.1);
        glBegin(GL_LINE);
        glVertex2f(-50, 0);
        glVertex2f(50, 0);
        glEnd();
        break;
        //--------------------------------
    case 1:
        glBegin(GL_LINES);
        glColor3f(1, 0, 0);
        glVertex2f(-50, 0);
        glColor3f(0, 0, 1);
        glVertex2f(50, 0);
        glEnd();
        break;
        //--------------------------------
    case 2:
        glBegin(GL_LINES);
        glVertex2f(-50, 0);
        glVertex2f(50, 0);

        glVertex2f(0, -50);
        glVertex2f(0, 50);
        glEnd();
        break;
        //--------------------------------
    case 3:
        glBegin(GL_LINE_STRIP);
        glColor3f(0, 1, 0);
        glVertex2f(0, 0);
        glVertex2f(50, 0);
        glVertex2f(50, 50);
        glVertex2f(-50, 50);
        glEnd();
        break;
        //--------------------------------
    case 4:
        glColor3f(0, 0, 1);
        glBegin(GL_LINE_LOOP);
        glVertex2f(0, 0);
        glVertex2f(50, 0);
        glVertex2f(50, 50);
        glVertex2f(-50, 50);
        glEnd();
        break;
        //--------------------------------
    case 5:
        glLineWidth(5);
        glBegin(GL_LINE_STRIP);
        glVertex2f(0, 0);
        glVertex2f(50, 0);
        glVertex2f(50, 50);
        glVertex2f(-50, 50);
        glEnd();
        glLineWidth(1);
        break;
    }
}

void GLWidget::resizeGL(int width, int height)
{
    glViewport(0, 0, width, height);//set viewport, don't rely on default values

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-width/2, width/2, -height/2, height/2, -1, 1);
}


void GLWidget::keyPressEvent(QKeyEvent *e)
{
    switch(e->key())
    {
    case 'A':
        sample  = sample < 5 ? sample + 1 : sample;
        break;
    case 'S':
        sample  = sample > 0 ? sample - 1 : sample;
    };

    ((QMainWindow*)this->parent())->setWindowTitle(QString::number(sample));

    updateGL();
}

在这里，我创建了一个新的布局，以便在页面中显示我的小部件。

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

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

    glW = new GLWidget(0, 0);
    QGridLayout *layout1 = new QGridLayout();
    QWidget *centralWidget1 = new QWidget(this);
    centralWidget1->setLayout(layout1);

    layout1->addWidget(glW);
    setCentralWidget(centralWidget1);
    //this->layout()->addWidget(glW);

  //  glW->setGeometry(0, 0, 640, 480);
  //  glW->setFocus();
}

MainWindow::~MainWindow()
{
    delete ui;
    delete glW;
}

Answer 1

导致其中一个问题是因为QGLWidget无法处理焦点，因此当您按下一个键时，您永远不会调用keyPressEvent，解决方案是使用setFocusPolicy()设置焦点策略：

GLWidget::GLWidget(QWidget *parent, QGLWidget *shareWidget)
    : QGLWidget(parent, shareWidget)
{
    sample = 0;
    setFocusPolicy(Qt::StrongFocus);
}

注意：

GL_LINE仅用作使用glPolygonMode的参数，因此该指令不会绘制任何行。

在以下link中，您可以找到完整的示例。

在Qt中绘制线条

1 个答案: