QML 的 Import语句及自定义类
首先应了解C++类的知识, 环境变量的概念和一点CMake和Javascript语法, 否则下面的解释可能有些难懂
Import语句, 共3种
1.import [] [as ]
例：import QtQuick 2.10 as Quick
这里QtQuick 2.10是一个模块(是一个类与头文件的组合, 后面会讨论)，Quick叫做namespace qualifier，用来引用QtQuick 2.10
还可以（这里“textwidgets"看起来应该是一个文件）：
import "../textwidgets" as MyModule
2.Directory Imports（也可以导目录）
import "" [as ]
3.JavaScript Resource Imports（javascript文件）
import "" as
上面例子中直接导入文件，那么这些文件在哪个目录呢?
根据帮助文档: QML Import Path
When an identified module is imported, the QML engine searches the import path for a matching module.
This import path, as returned by QQmlEngine::importPathList(), defines the default locations to be searched by the engine. By default, this list contains:
包括4种情况：
- The directory of the current file
- The location specified by QLibraryInfo::QmlImportsPath
- Paths specified by the QML_IMPORT_PATH environment variable
- The qrc:/qt-project.org/imports path inside the resources.
- 当前路径；
- QLibraryInfo::QmlImportsPath指定的路径；
- QML_IMPORT_PATH环境变量指定的路径；
- 资源文件中指定的路径：qrc:/qt-project.org/imports
#ifndef PERSON_H #define PERSON_H #include根据官方文档： C++ types are declared using the QML_ELEMENT and QML_NAMED_ELEMENT() macros and registered via the build system using QML_IMPORT_NAME and QML_IMPORT_MAJOR_VERSION. The import name and version given this way form a module that can be imported to access the types. This is most common in client applications which define their own QML object types in C++. 这里注意QML_ELEMENT, 它指明这个头文件对应的类是一个QML元素。根据帮助文档：原文如下： QML_ELEMENT：Declares the enclosing type or namespace to be available in QML, using its class or namespace name as the QML element name. 这里说明类名就是QML元素的名称。 NOTE: When classes have the same name but are located in different namespaces using QML_ELEMENT on both of them will cause a conflict. Make sure to use QML_NAMED_ELEMENT() for one of them instead. 如果有多个相同名称的类（处于不同命名空间），则使用QML_NAMED_ELEMENT() 宏来区分不同命名空间的类。 接下来在qml文件中引用它。 准备好了类，说明元素名已经确定了，import后面的模块如何确定呢？比如：#include //![0] class Person : public QObject { Q_OBJECT Q_PROPERTY(QString name READ name WRITE setName) Q_PROPERTY(int shoeSize READ shoeSize WRITE setShoeSize) QML_ELEMENT // 定义为QML元素 public: using QObject::QObject; QString name() const; void setName(const QString &); int shoeSize() const; void setShoeSize(int); private: QString m_name; int m_shoeSize = 0; }; //![0] #endif // PERSON_H
import People 1.0import这里会报错，说明找不到People这个模块：
Person { name: "Bob Jones" shoeSize: 12 }
这就需要使用构建工具 在CMake中加入：
qt_add_qml_module(adding // 添加目标--工程名 URI People // 类名 VERSION 1.0 QML_FILES example.qml NO_RESOURCE_TARGET_PATH )编译一次就没有问题了。 原理： https://doc.qt.io/qt-6/qtqml-syntax-imports.html https://doc.qt.io/qt-6/qtqml-syntax-directoryimports.html QML 引用C++类实例：https://code.qt.io/cgit/qt/qtdeclarative.git/tree/examples/qml/referenceexamples/adding?h=6.2