QT中qmlRegisterType qmlRegisterSingletonType的区别

客官°小女子只卖身不卖艺 2022-08-21 04:15 149阅读 0赞

qmlRegisterType qmlRegisterSingletonType

了解设计模式的肯定知道单根模式，这个qmlRegisterSingletonType函数意思能就是注册一个单根类型到QML中，看看他们的完整声明：

int qmlRegisterSingletonType(const char \*uri, int versionMajor, int versionMinor, const char \*typeName, QJSValue(\* ) ( QQmlEngine \*, QJSEngine \* ) callback)

int qmlRegisterSingletonType(const char \*uri, int versionMajor, int versionMinor, const char \*typeName,

QObject \*(\* ) ( QQmlEngine \*, QJSEngine \* ) callback)

int qmlRegisterSingletonType(const QUrl &url, const char \*uri, int versionMajor, int versionMinor, const char \*qmlName)

前两个函数通过回调函数返回类型的实例，第三个函数通过URL生成实例

// First, define the singleton type provider function (callback).
      static QJSValue example_qjsvalue_singletontype_provider(QQmlEngine *engine, QJSEngine *scriptEngine)
      {
          Q_UNUSED(engine)
    
          static int seedValue = 5;
          QJSValue example = scriptEngine->newObject();
          example.setProperty("someProperty", seedValue++);
          return example;
      }
    
      // Second, register the singleton type provider with QML by calling this function in an initialization function.
      #include <QtQml>
      ...
      qmlRegisterSingletonType("Qt.example.qjsvalueApi", 1, 0, "MyApi", example_qjsvalue_singletontype_provider);
      ...

qml中这样使用

import QtQuick 2.0
      import Qt.example.qjsvalueApi 1.0 as ExampleApi
      Item {
          id: root
          property int someValue: ExampleApi.MyApi.someProperty
      }

未写完，待续