Qt Call Slot From Different Thread
Qt的官方文档如下： void QObject::moveToThread ( QThread. targetThread ) Changes the thread affinity for this object and its children. The object cannot be moved if it has a parent. Event processing will continue in the targetThread. Calling a slot from another thread I have two threads, one is my interface to Skype (through their API), and one is the GUI thread. A lot of the Skype API functions are blocking, thus the separate thread is necessary. Now, if you call webobj-setsomeattribute(“hello”), you will see the value of the html element with id “#attrid” is set to “hello”. Note that although we connect the member msomeattribute to the qt property someattribute in the above example, it is not a required step. The signal mechanism alone can realize the delivery of data. I use Qt::QueuedConnection to execute this slot. Once in a while, the Master has to ask Worker to stop the calculation in between, and to terminate it prematurely I have provided the abortCalculation variable in the Worker object which it checks in each loop of the long-running calculation. Qt provides thread support in the form of platform-independent threading classes, a thread-safe way of posting events, and signal-slot connections across threads. This makes it easy to develop portable multithreaded Qt applications and take advantage of multiprocessor machines.
- Qt Call Slot In Different Thread
- Qt Call Slot From Another Thread
- Qt Call Slot From Different Threads
- Qt Call Slot From Different Thread Types
- Qt Invoke Slot Another Thread
Introduction
Remember old X-Window call-back system? Generally it isn't type safe and flexible. There are many problems with them. Qt offer new event-handling system - signal-slot connections. Imagine alarm clock. When alarm is ringing, signal is sending (emitting). And you're handling it as a slot.
Qt Call Slot In Different Thread
- Every QObject class may have as many signals of slots as you want.
- You can emit signal only from that class, where signal is.
- You can connect signal with another signal (make chains of signals);
- Every signal and slot can have unlimited count of connections with other.
- ATTENTION! You can't set default value in slot attributes. e.g.
void mySlot(int i = 0);
Connection
You can connect signal with this template:QObject::connect ( const QObject * sender, const char * signal, const QObject * receiver, const char * method);You have to wrap const char * signal and const char * method into SIGNAL () and SLOT() macros.
And you also can disconnect signal-slot:QObject::disconnect ( const QObject * sender, const char * signal, const QObject * receiver, const char * method);
Deeper
Widgets emit signals when events occur. For example, a button will emit a 'clicked' signal when it is clicked. A developer can choose to connect to a signal by creating a function (a 'slot') and calling the connect() function to relate the signal to the slot. Qt's signals and slots mechanism does not require classes to have knowledge of each other, which makes it much easier to develop highly reusable classes. Since signals and slots are type-safe, type errors are reported as warnings and do not cause crashes to occur.
For example, if a Quit button's clicked() signal is connected to the application's quit() slot, a user's click on Quit makes the application terminate. In code, this is written as
Qt Call Slot From Another Thread
connect(button, SIGNAL (clicked()), qApp, SLOT (quit()));
Qt Call Slot From Different Threads
Connections can be added or removed at any time during the execution of a Qt application, they can be set up so that they are executed when a signal is emitted or queued for later execution, and they can be made between objects in different threads.
Qt Call Slot From Different Thread Types
The signals and slots mechanism is implemented in standard C++. The implementation uses the C++ preprocessor and moc, the Meta-Object Compiler, included with Qt. Code generation is performed automatically by Qt's build system. Developers never have to edit or even look at the generated code.