如何在基类中使用来自qt中所有继承类的信号?

这永远不会起作用，因为这些类似乎在主线程中工作，并且在处理完成时，不会进行任何用户界面更新，并且您的应用程序被冻结。

在所有情况下，解决方案都必须从使繁忙指示器成为适当的属性开始 - 这将神奇地解决您的 Qt Quick 问题，您可以简单地绑定到该属性，而根本不需要显式使用信号。这就是属性通知的用途，QML会为您处理它们。您也不希望资源库是公共的 - 这是内部的只读状态。您还需要恒定正确的签名。

解决所有问题后，我们得到：

class ManagerEngine : public QObject {
Q_OBJECT
Q_PROPERTY(bool isProcessing READ isProcessing NOTIFY isProcessingChanged)
public:
using QObject::QObject; //for C++14 & up
bool isProcessing() const;
Q_SIGNAL void isProcessingChanged(bool);
protected:
void setIsProcessing(bool);
private:
bool m_isProccessing = false;
};
/// This method is not thread-safe
void ManagerEngine::setIsProcessing(bool p) {
if (p == m_isProcessing) return;
m_isProcessing = p; // precondition of the signal
return emit isProcessingChanged(m_isProcessing);
}
/// This method is not thread-safe
bool ManagerEngine::isProcessing() const {
return m_isProcessing;
}

如果希望处理是管理器引擎的所有实例共享的状态，请使其成为类的属性，而不是对象的属性。在C++中，static成员声明意味着它是类成员，而不是对象成员。

接口

class ManagerEngine : public QObject {
Q_OBJECT
Q_PROPERTY(bool isProcessing READ isProcessing NOTIFY isProcessingChanged)
public:
using QObject::QObject; //for C++14 & up
~ManagerEngine() override;
bool isProcessing() const;
Q_SIGNAL void isProcessingChanged(bool);
protected:
void setIsProcessing(bool);
private:
bool m_isProcessing = false; // per-object
static QAtomicInt m_processingCount; // per-class
};

实现

QAtomicInt ManagerEngine::m_processingCount;
ManagerEngine::~MangerEngine() {
setIsProcessing(false);
// Perhaps it'd be more appropriate instead to simply
// Q_ASSERT(!m_isProcessing) if the engine should not be destroyed
// during processing.
}
// This method is not thread-safe, but multiple engines can
// reside in different threads.
void ManagerEngine::setIsProcessing(bool p) {
if (p == m_isProcessing) return;
int const delta = p ? (+1) : (-1);
auto count = m_processingCount.load();
Q_ASSERT(count >= 0);
Q_ASSERT(p || count > 0);
m_isProcessing = p;
while (!m_processingCount.testAndSetOrdered(count, count+delta)) {
count = m_processingCount.load();
}
// The signal will be emitted only when the global state changes,
// and exactly once per global state change.
if ((count > 0) != ((count+delta) > 0))
emit isProcessingChanged(count > 0);
return;
}
// Note: Due to data races, it is not guaranteed that the result of
// this method is the same as the parameter in the isProcessingChanged
// signal. Only the signal's parameter is guaranteed to change state
// in a race-free fashion, i.e. always toggle (alternate) and never repeat.
bool ManagerEngine::isProcessing() const {
auto const count = m_processingCount.load();
Q_ASSERT(count >= 0);
Q_ASSERT(!m_isProcessing || count > 0);
return count > 0;
}