Qt 6.6.1 Build Error: Cannot invoke "String.length()" because "<parameter1>" is null

[8Observer8]

Hi,

I wrote a simple example that just show an OpenGL version. It works on Windows:

But when I try to run it on Android physical device (Redmi 4X) it shows errors:

main.cpp

// #ifdef _WIN32
// #include <windows.h>
// extern "C" __declspec(dllexport) DWORD NvOptimusEnablement = 0x00000001;
// extern "C" __declspec(dllexport) DWORD AmdPowerXpressRequestHighPerformance = 0x00000001;
// #endif

#include <QtGui/QOpenGLFunctions>
#include <QtGui/QSurfaceFormat>
#include <QtOpenGLWidgets/QOpenGLWidget>
#include <QtWidgets/QApplication>
#include <QtWidgets/QLabel>
#include <QtWidgets/QVBoxLayout>
#include <QtWidgets/QWidget>

class OpenGLWidget : public QOpenGLWidget, private QOpenGLFunctions
{
    Q_OBJECT

signals:
    void showInfoSignal(const QString &openGLVersion, const QString &shadingVersion, const QString &vendor);

private:
    void initializeGL() override
    {
        initializeOpenGLFunctions();
        glClearColor(0.f, 1.f, 0.f, 1.f);
        QString version(QString("OpenGL version: %1").arg((const char*) glGetString(GL_VERSION)));
        QString shadingLanguageVersion(QString("GLSL version: %1").arg((const char*) glGetString(GL_SHADING_LANGUAGE_VERSION)));
        QString vendor(QString("Vendor: %1").arg((const char*) glGetString(GL_VENDOR)));
        emit showInfoSignal(version, shadingLanguageVersion, vendor);
    }

    void paintGL() override
    {
        glClear(GL_COLOR_BUFFER_BIT);
    }
};

class MainWindow : public QWidget
{
    Q_OBJECT
public:
    MainWindow()
    {
        setWindowTitle("OpenGL Version");
        resize(300, 300);

        m_openGLVersionLabel = new QLabel();
        m_shadingLanguageVersionLabel = new QLabel();
        m_vendorLabel = new QLabel();
        OpenGLWidget *openGLWidget = new OpenGLWidget();

        m_openGLVersionLabel->setSizePolicy(QSizePolicy::Policy::Fixed, QSizePolicy::Policy::Fixed);
        m_shadingLanguageVersionLabel->setSizePolicy(QSizePolicy::Policy::Fixed, QSizePolicy::Policy::Fixed);
        m_vendorLabel->setSizePolicy(QSizePolicy::Policy::Fixed, QSizePolicy::Policy::Fixed);

        QVBoxLayout *layout = new QVBoxLayout();
        layout->addWidget(m_openGLVersionLabel);
        layout->addWidget(m_shadingLanguageVersionLabel);
        layout->addWidget(m_vendorLabel);
        layout->addWidget(openGLWidget);
        setLayout(layout);

        connect(openGLWidget, &OpenGLWidget::showInfoSignal, this, &MainWindow::showInfoSlot);
    }

private slots:
    void showInfoSlot(const QString &openGLVersion, const QString &shadingVersion, const QString &vendor)
    {
        m_openGLVersionLabel->setText(openGLVersion);
        m_shadingLanguageVersionLabel->setText(shadingVersion);
        m_vendorLabel->setText(vendor);
    }

private:
    QLabel *m_openGLVersionLabel;
    QLabel *m_shadingLanguageVersionLabel;
    QLabel *m_vendorLabel;
};

#include "main.moc"

int main(int argc, char *argv[])
{
    // QApplication::setAttribute(Qt::ApplicationAttribute::AA_UseDesktopOpenGL);
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

pro

QT += core gui openglwidgets widgets

win32: LIBS += -lopengl32

CONFIG += c++17

SOURCES += \
    main.cpp

TARGET = app

[8Observer8]

I solved the problem! Qt6 doesn't work with jdk-21. I has jdk-17 and installed jdk-21 in additional. Qt Creator automatically changed jdk-17 to jdk-21. I changed it back:

It works. I use scrcpy to show the physical Android screen to computer:

[8Observer8]

I tried to add the AA_UseOpenGLES attribute but I have the same errors above

int main(int argc, char *argv[])
{
    QApplication::setAttribute(Qt::ApplicationAttribute::AA_UseOpenGLES);
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

[8Observer8]

I wrote another example that shows one QOpenGLWidget without the MainWindow class and without signal/slots. It works on the Desktop but has the same errors when I try to build for Android:

main.cpp

#include <QtGui/QOpenGLFunctions>
#include <QtGui/QSurfaceFormat>
#include <QtOpenGLWidgets/QOpenGLWidget>
#include <QtOpenGL/QOpenGLBuffer>
#include <QtOpenGL/QOpenGLShaderProgram>
#include <QtWidgets/QApplication>

class OpenGLWidget : public QOpenGLWidget, private QOpenGLFunctions
{
public:
    OpenGLWidget()
    {
        resize(350, 350);
    }

private:
    void initializeGL() override
    {
        initializeOpenGLFunctions();
        glClearColor(0.4f, 0.8f, 0.9f, 1.f);

        qDebug() << "OpenGL Version:" << (const char*) glGetString(GL_VERSION);
        qDebug() << "GLSL Version:" << (const char*) glGetString(GL_SHADING_LANGUAGE_VERSION);
        qDebug() << "OpenGL Vendor:" << (const char*) glGetString(GL_VENDOR);

        QString vertexShaderSource =
            "attribute vec2 aPosition;\n"
            "void main()\n"
            "{\n"
            "    gl_Position = vec4(aPosition, 0.0, 1.0);\n"
            "}\n";

        QString fragmentShaderSource =
            "#ifdef GL_ES\n"
            "precision mediump float;\n"
            "#endif\n"
            "//out vec4 fragColor;\n"
            "void main()\n"
            "{\n"
            "    gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n"
            "}\n";

        m_program.addShaderFromSourceCode(QOpenGLShader::ShaderTypeBit::Vertex,
                                          vertexShaderSource);
        m_program.addShaderFromSourceCode(QOpenGLShader::ShaderTypeBit::Fragment,
                                          fragmentShaderSource);
        m_program.link();
        m_program.bind();

        float vertPositions[] = {
            -0.5f, -0.5f,
            0.5f, -0.5f,
            0.f, 0.5f
        };
        m_vertPosBuffer.create();
        m_vertPosBuffer.bind();
        m_vertPosBuffer.allocate(vertPositions, sizeof(vertPositions));
        m_program.setAttributeBuffer("aPosition", GL_FLOAT, 0, 2);
        m_program.enableAttributeArray("aPosition");
    }

    void paintGL() override
    {
        glClear(GL_COLOR_BUFFER_BIT);
        glDrawArrays(GL_TRIANGLES, 0, 4);
    }

private:
    QOpenGLShaderProgram m_program;
    QOpenGLBuffer m_vertPosBuffer;
};

int main(int argc, char *argv[])
{
    // QApplication::setAttribute(Qt::ApplicationAttribute::AA_UseDesktopOpenGL);
    QApplication::setAttribute(Qt::ApplicationAttribute::AA_UseOpenGLES);
    QApplication app(argc, argv);
    OpenGLWidget w;
    w.show();
    return app.exec();
}

pro

QT += core gui openglwidgets widgets

win32: LIBS += -lopengl32

CONFIG += c++17

SOURCES += \
    main.cpp

[8Observer8]

I solved the problem! Qt6 doesn't work with jdk-21. I has jdk-17 and installed jdk-21 in additional. Qt Creator automatically changed jdk-17 to jdk-21. I changed it back:

It works. I use scrcpy to show the physical Android screen to computer:

[swurl]

@8Observer8 Having the same issue on JDK 17. What SDK version do you have?

[8Observer8]

@swurl where to see the SDK version? I downloaded and installed it by clicking on the link a month ago:

When you click on the link above you will redirect to the Command Line Tools with this version:

[jsulm]

@8Observer8 said in Qt 6.6.1 Build Error: Cannot invoke "String.length()" because "<parameter1>" is null:

where to see the SDK version?

Maybe if you click on "SDK Manager"?

[8Observer8]