![我如何将它们连接到C]( "我如何将它们连接到C")
本文介绍了我有多个通过StackView推送的qml文件.我如何将它们连接到C ++的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我的项目包含6个qml文件:main.qml打开一个新的ApplicationWindow并声明工具栏.它还使用initalItem homescreen.qml来初始化StackView.在主屏幕上，我有不同的按钮，可通过stack.push("URL")打开不同的qml文件.除main.qml外，所有文件均以Item {}开头.我已经能够连接来自main.qml和home.qml的信号.但是我一直无法访问堆栈中较深的对象.我不知道是否要更改.cpp代码以访问其他对象，还是应该更改StackView的Initalization，以便在开始时就可以加载和访问所有文件.这是代码，细分为最基本的内容:
-
main.qml
ApplicationWindow {
Rectangle{
id: homeButton
objectName: "homeButton"
signal qmlSignal(string msg)
MouseArea {
onClicked: {stack.push({item:"qrc:/home.qml}); homeButton.qmlSignal("Hello")}
}
}
StackView{
initalItem: "qrc:/home.qml"
}
}
-
secondframe.qml//主屏幕后出现一个随机w qml文件
Item {
Rectangle{
id: test
objectName: "test"
signal qmlSignal(string msg)
MouseArea {
onClicked: {stack.push({item:"qrc:/thirdframe.qml}); test.qmlSignal("Hello")}
}
}
}
-
main.cpp
QApplication app (argc, argv);
QQmlEngine enigne;
QQmlComponent component(&engine, QUrl(QStringLiteral("qrl:/main.qml")));
QObject *object = componet.create();
QQmlComponent newcomponent(&engine, QUrl(QStringLiteral("qrl:/secondframe.qml")));
QObject *newobject = newcomponet.create();
MyClass myClass
QObject *home = object->findChild<QObject*>("homeButton"); // I'm able to connect to every Object in the main.qml or home.qml
QObject::connect(home,SIGNAL(qmlSignal(Qstring)), &myClass, SLOT(cppSlot(QString)));
QObject *test = newobject->findChild<QObject*>("test"); // Can't connect to the Objects in secondframe.qml
QObject::connect(test,SIGNAL(qmlSignal(Qstring)), &myClass, SLOT(cppSlot(QString)));
解决方案
一种比进入QML树并提取可能存在或可能不存在的对象更好的方法是为QML提供基于C ++的API.
>
-
创建一个基于QObject的类，该类具有QML需要能够作为插槽或Q_INVOKABLE
调用的方法class MyAPI : public QObject
{
Q_OBJECT
public slots:
void cppSlot(const QString &text);
};
-
创建该实例并将其公开给QML
MyAPI myApi;
QQmlEngine engine;
engine.rootContext()->setContextProperty("_cppApi", &myApi);
-
在QML中使用，就像"_cppApi"是对象ID一样
MouseArea {
onClicked: {stack.push({item:"qrc:/thirdframe.qml}); _cppApi.cppSlot("Hello")}
}
My Projects contains 6 qml Files: The main.qml opens a new ApplicationWindow and declares the toolbar. It also initalizes StackView with the initalItem homescreen.qml. On the Home Screen I have different buttons which open different qml Files, via stack.push("URL"). Besides the main.qml all Files start with Item{}.I've been able to connect signals from the main.qml and the home.qml. But I've been unable to access Objects that are deeper in the stack. I don't know if I hvae to change my .cpp code to access the other objects, or if I should change the Initalization of StackView, so that all Files are loaded and accessible at the beginning.Here is the code, broke down to the very basics:
main.qml
ApplicationWindow {
Rectangle{
id: homeButton
objectName: "homeButton"
signal qmlSignal(string msg)
MouseArea {
onClicked: {stack.push({item:"qrc:/home.qml}); homeButton.qmlSignal("Hello")}
}
}
StackView{
initalItem: "qrc:/home.qml"
}
}
secondframe.qml // A randomw qml File that comes after the Home Screen
Item {
Rectangle{
id: test
objectName: "test"
signal qmlSignal(string msg)
MouseArea {
onClicked: {stack.push({item:"qrc:/thirdframe.qml}); test.qmlSignal("Hello")}
}
}
}
main.cpp
QApplication app (argc, argv);
QQmlEngine enigne;
QQmlComponent component(&engine, QUrl(QStringLiteral("qrl:/main.qml")));
QObject *object = componet.create();
QQmlComponent newcomponent(&engine, QUrl(QStringLiteral("qrl:/secondframe.qml")));
QObject *newobject = newcomponet.create();
MyClass myClass
QObject *home = object->findChild<QObject*>("homeButton"); // I'm able to connect to every Object in the main.qml or home.qml
QObject::connect(home,SIGNAL(qmlSignal(Qstring)), &myClass, SLOT(cppSlot(QString)));
QObject *test = newobject->findChild<QObject*>("test"); // Can't connect to the Objects in secondframe.qml
QObject::connect(test,SIGNAL(qmlSignal(Qstring)), &myClass, SLOT(cppSlot(QString)));
解决方案
A way better approach than to reach into the QML tree and pull out objects that might or might not be there is to provide C++ based API to QML.
Create a QObject based class that has the methods QML needs to be able to call as slots or Q_INVOKABLE
class MyAPI : public QObject
{
Q_OBJECT
public slots:
void cppSlot(const QString &text);
};
Create an instance of that and expose it to QML
MyAPI myApi;
QQmlEngine engine;
engine.rootContext()->setContextProperty("_cppApi", &myApi);
Use in QML as if "_cppApi" is an object id
MouseArea {
onClicked: {stack.push({item:"qrc:/thirdframe.qml}); _cppApi.cppSlot("Hello")}
}
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