Qt ------ Thread Affinity （QObject::moveToThread: Cannot move objects with a parent）

简单的说，每个QObject的对象，都和某个创建对象所在的线程关联，如果把对象通过 moveToThread 移动到其他线程，这个对象不能有父对象，否则会出现 QObject::moveToThread: Cannot move objects with a parent

A QObject instance is said to have a thread affinity, or that it lives in a certain thread. When a QObject receives a queued signal or a posted event, the slot or event handler will run in the thread that the object lives in.

Note: If a QObject has no thread affinity (that is, if thread() returns zero), or if it lives in a thread that has no running event loop, then it cannot receive queued signals or posted events.

By default, a QObject lives in the thread in which it is created. An object's thread affinity can be queried using thread() and changed using moveToThread().

All QObjects must live in the same thread as their parent. Consequently:

• setParent() will fail if the two QObjects involved live in different threads.
• When a QObject is moved to another thread, all its children will be automatically moved too.
• moveToThread() will fail if the QObject has a parent.
• If QObjects are created within QThread::run(), they cannot become children of the QThread object because the QThread does not live in the thread that calls QThread::run().

Note: A QObject's member variables do not automatically become its children. The parent-child relationship must be set by either passing a pointer to the child's constructor, or by calling setParent(). Without this step, the object's member variables will remain in the old thread when moveToThread() is called.