Qt Quick快速入门之qml与C++交互
C++中使用qml对象,直接使用findChild获取qml对象,然后调用setProperty方法设置属性,当然必须在加载qml之后才能使用,不然findChild找不到对象,用法如下。
engine.load(QUrl(QStringLiteral("qrc:/main.qml"))); QObject * text_Msg = engine.rootObjects()[0]->findChild<QObject*>("text_Msg"); text_Msg->setProperty("color","red");
qml使用C++对象,这也是Qt中Model/View的实现方法,下面是一个例子。
首先,类需要继承自QObejct
class User:public QObject { Q_OBJECT Q_PROPERTY(QString Name READ Name WRITE setName NOTIFY NameChanged) Q_PROPERTY(int Age READ Age WRITE setAge NOTIFY AgeChanged) Q_PROPERTY(QString Message READ Message WRITE setMessage NOTIFY MessageChanged) public: User(); User(string name,int age); QString Name(); void setName(QString name); int Age(); void setAge(int age); QString Message(); void setMessage(QString message); signals: void NameChanged(); void AgeChanged(); void MessageChanged(); public slots: void editOk(); private : QString m_name; int m_age; QString m_message; };
User::User() { this->setName(""); this->setAge(0); } User::User(string name, int age) { QString q_name = QString::fromStdString(name); this->setName(q_name); this->setAge(age); } QString User::Name() { return m_name; } void User::setName(QString name) { m_name = name; emit NameChanged(); setMessage(QString("名称改变为:%1").arg(name)); } int User::Age() { return m_age; } void User::setAge(int age) { m_age = age; emit AgeChanged(); setMessage(QString("年龄改变为:%1").arg(age)); } QString User::Message() { return m_message; } void User::setMessage(QString message) { m_message = message; emit MessageChanged(); } void User::editOk() { setMessage("您点击了确定按钮"); }
然后,需要向qml中注册这个类,这样我们在qml中就可以导入这个类了
qmlRegisterType<User>("Models.User",1,0,"UserModel");
import Models.User 1.0
通常,直接将对象设置到qml对象的上下文,然后在qml中使用C++对象的属性
QQmlApplicationEngine engine; QQmlContext* context = engine.rootContext(); User* userModel = new User("测试",20); context->setContextProperty("testUserModel",userModel);
GridLayout{ anchors.centerIn: parent width:300 columnSpacing: 10 rowSpacing: 10 rows:4 columns:2 Item{ Layout.row: 0 Layout.column: 0 width:100 height:30 Text{ text:"Name:" anchors.centerIn: parent } } Item{ Layout.row: 0 Layout.column: 1 Layout.fillWidth: true height:30 TextField{ anchors.verticalCenter: parent.verticalCenter width:parent.width height:24 id:textfield_Name text: testUserModel.Name onEditingFinished: { testUserModel.Name = textfield_Name.text; } } } Item{ Layout.row: 1 Layout.column: 0 width:100 height:30 Text{ text:"Age:" anchors.centerIn: parent } } Item{ Layout.row: 1 Layout.column: 1 Layout.fillWidth: true height:30 TextField{ anchors.verticalCenter: parent.verticalCenter width:parent.width height:24 id:textfield_Age text:testUserModel.Age onEditingFinished: { testUserModel.Age = textfield_Age.text; } } } Item{ Layout.row: 2 Layout.column: 0 Layout.fillWidth: true height: 50 Layout.columnSpan: 2 RowLayout{ anchors.centerIn: parent Button{ id:button_OK text:"确定" action: button_OK_Action onClicked:{ testUserModel.editOk(); } } Button{ id:button_Cancel text:"取消" onClicked: { Qt.quit(); } } } } Item{ Layout.row: 3 Layout.column: 0 Layout.fillWidth: true height: 30 Layout.columnSpan: 2 Text { id: text_Msg objectName: "text_Msg" text: testUserModel.Message anchors.fill: parent verticalAlignment: Qt.AlignVCenter } } }
在qml中绑定C++对象的属性时,其实是执行C++对象属性的READ方法;而设置属性时,则是执行WRITE方法;C++属性的NOTIFY方法用于属性变更通知,当我们调用该方法时(通常在前面加上emit表示这是个信号方法),qml中的属性绑定就会再次执行READ方法。
下面是效果,编辑框失去焦点时,就会设置属性,进而调用C++对象的WRITE方法,然后在WRITE方法中更新其他属性。