Qt6中如何接收触摸事件？多触点无响应问题排查

一、初始触摸事件启用尝试及编译错误 #

• 尝试在main.cpp中设置应用属性以启用触摸事件：

  QApplication::setAttribute(Qt::ApplicationAttribute::WA_AcceptTouchEvents);
  

  编译报错：error: no member named 'WA_AcceptTouchEvents' in 'Qt::ApplicationAttribute'
  IntelliSense索引显示该属性存在，但实际编译不通过，怀疑Qt Creator索引异常

• 调整代码省略枚举类限定：

  QApplication::setAttribute(Qt::WA_AcceptTouchEvents);
  

  编译报错：error: cannot initialize a parameter of type 'Qt::ApplicationAttribute' with an rvalue of type 'Qt::WidgetAttribute'

• 尝试在QOpenGLWindow构造函数中调用setAttribute：
  构造函数代码：

  OpenGLWindow::OpenGLWindow()
  {
      setTitle("OpenGL ES 2.0, Qt6, C++");
      resize(350, 350);
      setAttribute(Qt::WA_AcceptTouchEvents);
  }
  

  编译报错：error: use of undeclared identifier 'setAttribute'; did you mean 'QInputMethodEvent::Attribute'?

二、项目pro文件配置 #

QT += core gui opengl widgets

CONFIG += c++17

# You can make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
# disables all the APIs deprecated before Qt 6.0.0
# DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000

SOURCES += \
    main.cpp \
    opengl_window.cpp

HEADERS += \
    opengl_window.h

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

三、重写touchEvent后多触摸失效问题 #

根据Qt官方文档说明：

Unlike widgets, QWindows receive touch events always, there is no need to opt in. When working directly with a QWindow, it is enough to reimplement QWindow::touchEvent()

重写touchEvent代码如下：

void OpenGLWindow::touchEvent(QTouchEvent *event)
{
    switch (event->type())
    {
        case QEvent::TouchBegin:
            qDebug() << "counter = " << m_counter;
            m_counter++;
            break;
    }
}

真机运行时出现异常：单指触摸屏幕会打印counter = 0，但按住一根手指再用另一根手指触摸时，不会触发counter = 1的打印，多触摸功能未生效。

内容的提问来源于stack exchange，提问作者8Observer8