如何使用自定义Qt类型与QML信号？ [英] How to use a custom Qt type with a QML signal?

问题描述

我在我的Qt 5.2 qml应用程序中创建了一个自定义类型

 类设置：public QObject 
 { 
 Q_OBJECT 
 Q_PROPERTY（QString key READ key WRITE setKey）
 Q_PROPERTY（QVariant value READ value WRITE setValue）
 
 public：
设置（QObject * parent = 0）; 
 
 QString key（）const; 
 void setKey（QString const& key）; 
 
 QVariant value（）const; 
 void setValue（QVariant const& value）; 
 
 private：
 QString m_key; 
 QVariant m_value; 
}; 
  

并在我的主函数中注册：

  int main（int argc，char * argv []）
 {
 QApplication app（argc，argv） 
 
 qmlRegisterType< Setting>（Setting，1,0，Setting）; 
 
 // ... 
} 
  

我想有一个按钮，其中有一个信号与我的自定义类型作为参数：

  import设置1.0 
 
 Button 
 {
 signal settingChanged（string，Setting）
 
 // ... 
} 
  
 
 
 
每次按下按钮，信号都会发出。
 
 
 
我的qml信号与我的C ++槽
  QObject :: connect（myButton，SIGNAL（settingChanged（QString，Setting） SLOT（settingChanged（QString，Setting）））; 
  
 Qt说
 code> QObject :: connect：没有这样的信号Button_QMLTYPE_41_QML_45 :: settingChanged（QString，Setting）in ... 
  
如果我从信号定义中删除我的自定义类型
 按钮
 {
信号settingChanged（string）
 
 // ... 
} 
  
并修改连接调用
  QObject :: connect（myButton，SIGNAL（settingChanged（QString）），this，SLOT （QString）））; 
  
连接调用工作。
 
 
 
可以在我的应用程序的qml部分中使用我的自定义qml类型设置。 
 
 
 
谢谢！
在我仔细阅读了Qt文档后，我在这里找到了答案。
 
 
 
 
  http：// qt-project。 org / doc / qt-5 / qtqml-cppintegration-interactqmlfromcpp.html＃connecting-to-qml-signals  
 
 
 
文档说
 
 
当使用QML对象类型作为信号参数时，参数 
 应该使用var作为类型，并且应该使用QVariant类型在C ++中接收该值 
 。
 
 
因此，设置的qml描述中的信号定义必须替换为 var 。
  import设置1.0 
 
按钮
 {
信号settingChanged（string，var）
 
 // ... 
} 
  
要连接qml信号与C ++槽，代码必须
  Object :: connect（myButton，SIGNAL（settingChanged（QString，QVariant） ），this，SLOT（settingChanged（QString，QVariant）））; 
  
此时连接工作正常！
 
 
 
为了使整个事情运行， QVariant 必须被投射到插槽内的正确类型。在我的情况下，一个设置类型。
  void Foo :: settingChanged （QString name，QVariant const& var）
 {
 Setting * setting = qobject_cast< Setting *>（var.value< QObject *> 
 
 // ... 
} 
  
 
I've created a custom type inside my Qt 5.2 qml application
class Setting : public QObject
{
    Q_OBJECT
    Q_PROPERTY(QString key READ key WRITE setKey)
    Q_PROPERTY(QVariant value READ value WRITE setValue)

public:
    Setting(QObject * parent = 0);

    QString key() const;
    void setKey(QString const & key);

    QVariant value() const;
    void setValue(QVariant const & value);

private:
    QString m_key;
    QVariant m_value;
};
and registered it in my main function:
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    qmlRegisterType<Setting>("Setting", 1,0, "Setting");

    // ...
}
In my application I would like to have a button that has a signal with my custom type as a parameter:
import Setting 1.0

Button
{
    signal settingChanged(string, Setting)

    // ...
}
Every time I hit the button the signal should be emitted.

If I try to connect my qml signal with my C++ slot
QObject::connect(myButton, SIGNAL(settingChanged(QString, Setting)), this, SLOT(settingChanged(QString, Setting)));
Qt says
QObject::connect: No such signal Button_QMLTYPE_41_QML_45::settingChanged(QString, Setting) in ...
If I remove my custom type from the signal definition
Button
{
    signal settingChanged(string)

    // ...
}
and modify the connect call
QObject::connect(myButton, SIGNAL(settingChanged(QString)), this, SLOT(settingChanged(QString)));
the connect call worked.

I could use my custom qml type Setting inside the qml part of my application. But what I do wrong if I would like to use it with my signal settingChanged?

Thanks!
解决方案
After I've readed the Qt documentation very carefully, I've found the answer here

http://qt-project.org/doc/qt-5/qtqml-cppintegration-interactqmlfromcpp.html#connecting-to-qml-signals

The documentation says

  
When a QML object type is used as a signal parameter, the parameter
  should use var as the type, and the value should be received in C++
  using the QVariant type.
So, the signal definition inside the qml description of Setting has to be replaced with var.
import Setting 1.0

Button
{
    signal settingChanged(string, var)

    // ...
}
To connect the qml signal with the C++ slot, the code has to be
Object::connect(myButton, SIGNAL(settingChanged(QString, QVariant)), this, SLOT(settingChanged(QString, QVariant)));
At this point the connection worked!

To make the whole thing running, the QVariant has to be casted to the right type inside the slot. In my case to a Setting type.
void Foo::settingChanged(QString name, QVariant const & var)
{
    Setting * setting = qobject_cast<Setting*>(var.value<QObject*>());

    // ...
}


                        
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