在C++中获取应用程序窗口的大小

Get Size of ApplicationWindow in C++

本文关键字：窗口 应用程序 C++ 获取      更新时间：2023-10-16

如何在C++中获取QML应用程序窗口的大小？

QQmlApplicationEngine engine;
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
if (engine.rootObjects().isEmpty())
return -1;
QObject *application_object = engine.rootObjects().first();
// Throws ApplicationWindow_QMLTYPE_11::height(int), no such signal
QObject::connect(application_object, SIGNAL(height(int)), &my_obj_here, SLOT(set_game_height(int)));
QObject::connect(application_object, SIGNAL(width(int)), &my_obj_here, SLOT(set_game_width(int)));
return app.exec();

我意识到我也没有获得应用程序窗口内容的大小(减去工具栏、菜单栏等(，但我如何访问它？

尝试使用property方法访问window_object上的window属性将返回 null 指针。

一种可能的解决方案是使用QQmlProperty来获取QQuickItem，然后heightChanged和widthChanged信号连接，这些信号只通知属性已更改但不指示值，因此必须使用方法height()和width()。

QObject *topLevel = engine.rootObjects().first();
QQuickItem *contentItem =qvariant_cast<QQuickItem *>(QQmlProperty::read(topLevel, "contentItem"));
if(contentItem){
QObject::connect(contentItem, &QQuickItem::heightChanged,
[&my_obj_here, contentItem](){
my_obj_here.set_game_height(contentItem->height());
});
QObject::connect(contentItem, &QQuickItem::widthChanged, 
[&my_obj_here, contentItem](){
my_obj_here.set_game_width(contentItem->width());
});
}

另一种解决方案是在QML端建立连接，为此您必须创建q-property：

class GameObject: public QObject{
Q_OBJECT
Q_PROPERTY(int game_width READ game_width WRITE set_game_width NOTIFY game_widthChanged)
Q_PROPERTY(int game_height READ game_height WRITE set_game_height NOTIFY game_heightChanged)
public:
using QObject::QObject;
int game_width() const{
return m_width;
}
void set_game_width(int width){
if(width == m_width)
return;
m_width = width;
emit game_widthChanged();
}
int game_height() const{
return m_height;
}
void set_game_height(int height){
if(height == m_height)
return;
m_height = height;
emit game_heightChanged();
}
signals:
void game_widthChanged();
void game_heightChanged();
private:
int m_width;
int m_height;
};

主.cpp

...
GameObject my_obj_here;
QQmlApplicationEngine engine;
engine.rootContext()->setContextProperty("my_obj_here", &my_obj_here);
...

主.qml

ApplicationWindow{

Connections{
target: contentItem
onHeightChanged:
my_obj_here.game_height = height
onWidthChanged:
my_obj_here.game_width = width
}
...
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