[英]Getting 'unregistered datatype' error in QML when Q_GADGET struct is in a separate header file
[英]How to create new instance of a Q_GADGET struct in QML?
我可以发出带有Q_GADGET标记的结构信号,从C ++到QML。
是否有可能将这样的结构从QML发送到C ++插槽? 我的代码在第一步失败:在QML中创建实例。
这段代码在第一行失败了......
var bs = new BatteryState()
bs.percentRemaining = 1.0
bs.chargeDate = new Date()
DataProvider.setBatteryState(bs)
......有错误:
qrc:///main.qml:34: ReferenceError: BatteryState is not defined
我可以从C ++向QML发出一个BatteryStatus结构,但是我想将一个参数作为单个参数发送回一个插槽。
这是BatteryState.h和BatteryState.cpp:
// BatteryState.h
#pragma once
#include <QDate>
#include <QMetaType>
struct BatteryState
{
Q_GADGET
Q_PROPERTY(float percentRemaining MEMBER percentRemaining)
Q_PROPERTY(QDate date MEMBER date)
public:
explicit BatteryState();
BatteryState(const BatteryState& other);
virtual ~BatteryState();
BatteryState& operator=(const BatteryState& other);
bool operator!=(const BatteryState& other) const;
bool operator==(const BatteryState& other) const;
float percentRemaining;
QDate date;
};
Q_DECLARE_METATYPE(BatteryState)
// BatteryState.cpp
#include "BatteryState.h"
BatteryState::BatteryState()
: percentRemaining(), date(QDate::currentDate())
{}
BatteryState::BatteryState(const BatteryState& other)
: percentRemaining(other.percentRemaining),
date(other.date)
{}
BatteryState::~BatteryState() {}
BatteryState&BatteryState::operator=(const BatteryState& other)
{
percentRemaining = other.percentRemaining;
date = other.date;
return *this;
}
bool BatteryState::operator!=(const BatteryState& other) const {
return (percentRemaining != other.percentRemaining
|| date != other.date);
}
bool BatteryState::operator==(const BatteryState& other) const {
return !(*this != other);
}
我在main.cpp中注册了这个类型:
qRegisterMetaType<BatteryState>();
建议?
你没有在QML中创建Q_GADGET
,QML对象需要是QObject
派生的,并且不是通过new
创建的 - 只适用于JS对象。 小工具只是生成元数据,以便您可以从QML访问其成员并传递,这就是它。
是否有可能将这样的结构从QML发送到C ++插槽?
可以发送,但不会在QML中创建。 它可以从C ++函数返回到QML,也可以作为某个对象的属性公开。
struct Test {
Q_GADGET
Q_PROPERTY(int test MEMBER test)
public:
Test() : test(qrand()) {}
int test;
Q_SLOT void foo() { qDebug() << "foo"; }
};
class F : public QObject { // factory exposed as context property F
Q_OBJECT
public slots:
Test create() { return Test(); }
void use(Test t) { qDebug() << t.test; }
};
// from QML
property var tt: F.create()
Component.onCompleted: {
F.use(F.create()) // works
var t = F.create()
console.log(t.test) // works
F.use(t) // works
console.log(tt.test) // works
F.use(tt) // works
tt.test = 555
F.use(tt) // works
t.test = 666
F.use(t) // works
t.foo() // works
}
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