[原创]如何在Qml和C++类之间进⾏交互（枚举，成员变量，成 员函数）
在QtQuick项⽬中，我们可能会⽤到Qt的各种库(QSettings, QtXml等)，这个时候就要我们去解决Qt库和Qml交互的问题，即C++和Qml的交互，特别当我们需要从Qml访问C++类的成员。要想在Qml中访问C++类，要分别在⼏个⽂件中做⼀些前提⼯作，下⾯⽤我在goodoffood项⽬中的代码作为⽰例：
Settings.h
// Settings继承Qt的QSettings类
// ⽤来存储程序运⾏时所需的数据信息（是否第⼀次启动isFristBoot，当前的语⾔currentLanguage等） class Settings: public QSettings {
Q_OBJECT
// 导出成员变量，供外部访问
// expose method to qml context
Q_PROPERTY (LanguageType currentLanguage READ getLanguage WRITE setLanguage NOTIFY languageChanged) // 导出currentLanguage及对应的get，set接⼝ Q_PROPERTY (bool firstBoot READ getFirstBoot WRITE setFirstBoot) // 导出firstBoot及对应的get，set接⼝
Q_PROPERTY (bool accept READ getAccept WRITE setAccept) // 导出accept及对应的get，set接⼝
Q_ENUMS(LanguageType) // 导出枚举类型
public:
enum LanguageType {
Null = 0,
LanguageZh,
LanguageTw,
LanguageEn,
LanguageDefault = LanguageEn
};
public:
Settings();
Settings(const QString &organization, const QString &application);
public:
void loadSettings();
LanguageType getLanguage() const;
void setLanguage(LanguageType language);
bool getFirstBoot() const;
void setFirstBoot(bool value);
bool getAccept() const;
void setAccept(bool value);
void setAppPath(const QString &folder);
// 导出成员函数，供外部调⽤
Q_INVOKABLE QString getXmlFilename(LanguageType language) const;
Q_INVOKABLE QString getSourceFilename(LanguageType language) const;
signals:
void languageChanged(LanguageType language);
private:
LanguageType currentLanguage; // save the language type
};
⼆、给C++类的包名（通过这个⽅法就可以在Qml中访问C++类）
main.cpp
qmlRegisterType<CSettings>("settings",1,0,"CSettings"); // 1,0为版本号的命名，第⼀个settings为路径名，第⼆个CSettings为类名
⽰例⽤法：
Language.qml:
// import QtQuick 1.0 // to target S60 5th Edition or Maemo 5
import QtQuick 1.1
kia.symbian 1.1
import settings 1.0 // 导⼊包名，有点类似Java
import ".."
import "../script/Logic.js"as Logic
Page {
Column {
id: buttonBox
spacing: 50
ToolButton {
text: "简体中⽂"
iconSource: "../images/languagezh.png"
onClicked: Logic.setCurrentLanguage(0)
platformStyle: ToolButtonStyle {acceptlanguage
buttonWidth: parent.width /2
}
}
...
...
...
} // end column
}
Logic.js:
function setCurrentLanguage(index)
{
switch (index) {
case0: {
Settings.currentLanguage = CSettings.LanguageZh; // 使⽤C++类的枚举值break;
}
case1: {
Settings.currentLanguage = CSettings.LanguageTw;
break;
}
case2: {
Settings.currentLanguage = CSettings.LanguageEn;
break;
}
default: break;
}
}
三、设置Qml上下⽂（通过此步骤就可以在Qml中访问C++类的对象）Settings settings("com.huistrong","goodoffood");
QmlApplicationViewer viewer;
⽰例⽤法
main.qml:
PageStackWindow {
id: appWindow
// Qml访问Settings类的成员变量currentLanguage
property int language: Settings.currentLanguage
...
...
}
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