Javascript在QML中等待

我有两个Javascript函数fun1,fun2在QML中,并希望fun2在另一个(fun1)完成之后执行一个(),更准确地说,如何在完成fun2()后启动.是一个用C++编写的函数,通过继承,如下所示:ImageReaderfun1ImageReaderQImageProvider

function fun1(){
    ImageReader.magic(photo);
}
function fun2(){
    myImg.source = ""; 
    myImg.source = "image://ImageReader";
}
fun1();
fun2();

使用场景是我想用C++处理图像,当处理完成后,通过QML Image项显示它.

好的,我只想总结那些将寻找相同解决方案的人.

至少有两种方法可以做到这一点:

任务完成后,从C++对象发出信号.

将JS函数传递给C++,这将在任务完成时调用.

测试C++对象声明:

class MyItem : public QObject
{
    Q_OBJECT

public:
    MyItem(QObject *parent = 0);
    Q_INVOKABLE void someAsyncFunc();
    Q_INVOKABLE void someAnotherAsyncFunc(QJSValue value);

signals:
    void someAsyncFuncFinished();
};

MyItem::MyItem(QObject *parent) :
QObject(parent) {}

void MyItem::someAsyncFunc()
{
    // do some work here
    emit someAsyncFuncFinished();
}

void MyItem::someAnotherAsyncFunc(QJSValue value) {
    // do some work here
    if (value.isCallable()) {
        value.call();
    }
}

static QObject *my_singleton_provider(QQmlEngine *engine, QJSEngine *scriptEngine)
{
    Q_UNUSED(engine)
    Q_UNUSED(scriptEngine)
    static MyItem *item = nullptr;
    if(!item)
        item = new MyItem();
    return item;
}

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    qmlRegisterSingletonType("Qt.MyTest", 1, 0, "MyItem", my_singleton_provider);

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    return app.exec();
}

Item {
    id: testItem

    function func1()
    {
        console.log("func1 executing...")
        MyItem.someAsyncFuncFinished.connect(func2);
        MyItem.someAsyncFunc();
    }

    function func2()
    {
        console.log("func2 executing...")
    }

    Component.onCompleted: func1();
}

Item {
    id: testItem

    function func1()
    {
        console.log("func1 executing...")
        MyItem.someAnotherAsyncFunc(func2);
    }

    function func2()
    {
        console.log("func2 executing...")
    }

    Component.onCompleted: func1();
}