QObject :: setParent:无法设置父级，新的父级在另一个线程中 [英] QObject::setParent: Cannot set parent, new parent is in a different thread

问题描述

问候

我正在上一个课.

class MyClass : public QObject
{
    Q_OBJECT

public:
    Q_INVOKABLE QVariant status();

public:
    MyClass(ClassX * classX);

public slots:
    void slotA();
    void slotB();

signals:
    void signalA();
    void signalB();

private:
    void init();
    void doSomething();

private:
    ClassX * classX;
    ClassA classA;
    ClassB classB;
};

在MyClass的构造函数中，我将classX设置为this.classX，在init()中，我将connect的某些classX信号设置为MyClass插槽，反之亦然，在someFunction()中我使用classA和classB.

In MyClass's constructor, I set classX to this.classX and in init(), I connect some of classX signals to MyClass slots and wise-versa and in someFunction() i use classA and classB.

在主线程的controller类中，创建MyClass对象并在其他线程中运行它.

In my controller class in main thread, I create MyClass object and run it inside different thread.

MyClass * myClass = new MyClass(classX);
connect(&myClassThread, SIGNAL(started()), myClass, SLOT(init()));
myClass->moveToThread(&myClassThread);
myClassThread.start();

我在qDebugger中看到以下警告.

QObject::setParent: Cannot set parent, new parent is in a different thread

谁能告诉我为什么我得到那个警告?

Can anyone tell me why i get that warning ?

感谢进阶

PS 1:在主线程中创建的classX.

PS 1: The classX created in main thread.

PS 2:请记住，一切正常，我没有任何问题，我只想知道此警告的原因以及解决方法.

PS 2 : Remember, Everything work fine and i don't have any problem, I just want to know the reason of this warning and how to fix it.

PS 3:我还在主线程中使用以下命令来显示javascript中的对象.

PS 3 : I also use the following command in main thread to expose the object in javascript.

webFrame->addToJavaScriptWindowObject("myClassObject", myClass);

QThread myClassThread是类成员.

Edit 1 : QThread myClassThread is class member.

我相信信息匮乏，你们感到困惑，对此我感到抱歉.

Edit 2 : I believe the lack of information, confused you guys and i'm sorry about that.

MyClass的构造函数是这样的:

The constructor of MyClass is like this :

MyClass::MyClass(ClassX * classX)
{
     this.classX = classX;
}

推荐答案

让我们说清楚. 您的代码无法正常运行.这就是框架告诉您的内容.

Let's be clear. Your code is not working as you intended it to work. That is what the framework is telling you.

QObject :: setParent:无法设置父级，新的父级位于另一个 线程

QObject::setParent: Cannot set parent, new parent is in a different thread

这意味着某个对象(怀疑为myClass)的所有插槽和信号都不会在与预期线程相同的线程中执行.这里的问题与myClass和classX对象的父对象有关

This means all slots and signals of a certain object (suspected myClass) will not be executed in the same thread as the one expected. The issue here revolve about the parent of either myClass andclassX objects

可能性I:myClass-> moveToThread(& myClassThread);失败

原因: myClass已设置了一个父项.这是禁止的.

Cause: myClass has a parent already set. which is forbidden.

这意味着init()将由线程对象myClassThread的线程触发.就线程和事件而言，这几乎与您做的

It mean that init() will be triggered by the thread of the thread object myClassThread. Thread-wise and event-wise, this is almost the same as if you did

MyClass * myClass = new MyClass(classX);
QMetaObject::invokeMethod(myClass, "init", Qt::QueuedConnection);

可能性II:init()违反了线程亲和力

原因: "classX"或一个神秘的相关对象已设置了父对象或无法移动到另一个线程.思考小部件.

Cause: `classX``or a mysterious related object has a parent already set or is not movable to another thread. Think widget.

moveToThread成功，您在一个线程中具有MyClass，在另一个线程中具有classX.构造myClass时已提供classX. myClass现在正在操纵另一个线程中的对象，并且如果没有进一步的代码，我们将无法承担线程安全性或正确的子父亲缘关系.仔细检查MyClass :: MyClass`和MyClass :: init.

moveToThread succeed, you have MyClass in one thread, and classX in another thread. You have provided classX when constructing myClass. myClass is now manipulating an object in another thread, and without further code we cannot assume thread safety or correct child parent affinity. Review MyClass::MyClass` and MyClass::init carefully.

发生了什么?

在调试器中的控制器代码中中断，然后查看线程ID.然后使用init方法插入调试器.

Break in the debugger in controller code and look at the thread id. Then break in the debugger in the init method.

• 如果是同一线程，情况一
• 否则就是案例

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