有没有QApplication :: exec（）使用Qt的方法？ [英] Is there a way to use Qt without QApplication::exec()?

问题描述

有没有一个安全的方式来使用Qt而不调用QApplication :: exec（）？

我有多个不同的对象在多个资源上执行长时间的进程（至少有一个正在与Web应用程序服务器通信）。我正在制作一个GUI应用程序，提示用户在适当的时间输入这些不同的进程。我想让我的'流'逻辑 - 逻辑，决定下一步做什么 - 在一个地方，而不是一个GUI对象，如对话框类。我在想我可以这样做：

  ... 
 
 wait_dialog dlg; 
 dlg.setModal（false）; 
 dlg.show（）; //应该返回... 
 
 netobject.start_long_lived_process_that_happens_on_other_thread（& completion_callback）; 
 while（！completion_callback_called（））
 {
 qApp-> processEvents（）; 
 netobject.pump_callbacks（）; 
 magically_avoid_busywait_while_still_servicing_qt_somehow（）; 
} 
 
 dlg.hide（）; 
 
 ... 
  

从Qt的角度来看，这是否安全？有没有一个好的方式实现 magically_avoid_busywait_while_still_servicing_qt_somehow（）？

我要在这里完成的是以最明确的方式写我们的处理流程。我想要一个单一的功能：

  show_a_non_modal_wait_dialog（）
 
 start_some_processing_1（）
 
 wait_for_processing_1_to_finish（）
 
 dismiss_non_modal_wait_dialog（）
 
 show_modal_input_dialog（）
 
如果（已取消）返回
 
 show_a_non_modal_wait_dialog（）
 
 start_some_processing_2（）
 
 wait_for_processing_2_to_finish（）
 
 dismiss_non_modal_wait_dialog（）
 
 show_modal_input_dialog（） 
 
如果（取消）返回
 
 ... 
  

我真正想避免的是在Qt窗口小部件和窗口中进行处理。此外，处理对象本身完全独立于Qt。我想我想要做的是在单个函数中创建一个控制器，其中包含几个帮助器回调和状态变量。

解决方案

你想要的是一个事件循环，其他应用程序的主事件循环。这可以使用 QEventLoop ：

  wait_dialog dlg; 
 dlg.setModal（false）; 
 dlg.show（）; //应该返回... 
 
 QEventLoop循环; 
 connect（& netobject，SIGNAL（done（）），& loop，SLOT（quit（）））; 
 netobject.start_long_lived_process_that_happens_on_other_thread（）; 
 
 loop.exec（）; // BLOCKING（非忙）直到quit（）通过signal完成调用（）
  

这是（在我眼中）干净的代码，这需要你的netobject类成为一个QObject，并实现一个信号 done（）（这比提供回调更干净） / p>

现在，您可以将整个代码包装在一个将自动阻止调用的函数中，因此如果您希望，可以从对话框返回一些结果。

Is there a safe way to use Qt without calling QApplication::exec()?

I have a number of different objects that are carrying out long-lived processes on multiple resources (at least one of them is communicating with a web application server). I'm making a GUI application that prompts the user for input at the right time for these different processes. I'd like to have my 'flow' logic - the logic that determines what to do next - in one place and not in a GUI object like a dialog class. I was thinking that I could do something like this:

...

wait_dialog dlg;
dlg.setModal( false );
dlg.show(); // Should return...

netobject.start_long_lived_process_that_happens_on_other_thread( &completion_callback );
while ( !completion_callback_called() )
{
    qApp->processEvents();
    netobject.pump_callbacks();
    magically_avoid_busywait_while_still_servicing_qt_somehow();
}

dlg.hide();

...

Is this safe, from Qt's point of view? Is there a 'good' way of implementing magically_avoid_busywait_while_still_servicing_qt_somehow()?

What I'm trying to accomplish here is to write our processing flow in the most explicit way possible. I'd like a single function that does this:

 show_a_non_modal_wait_dialog()

 start_some_processing_1()

 wait_for_processing_1_to_finish()

 dismiss_non_modal_wait_dialog()

 show_modal_input_dialog()

 if ( cancelled ) return

 show_a_non_modal_wait_dialog()

 start_some_processing_2()

 wait_for_processing_2_to_finish()

 dismiss_non_modal_wait_dialog()

 show_modal_input_dialog()

 if ( cancelled ) return

 ...

What I really want to avoid is kicking off and waiting for the processing inside Qt widgets and windows. Also, the processing objects themselves are entirely independent of Qt. I suppose what I'm trying to do is create a controller in a single function with a few helper callbacks and status variables.

解决方案

What you want is an event loop other that the application's main event loop. This can be done using the QEventLoop:

wait_dialog dlg;
dlg.setModal( false );
dlg.show(); // Should return...

QEventLoop loop;
connect(&netobject, SIGNAL(done()), &loop, SLOT(quit()));
netobject.start_long_lived_process_that_happens_on_other_thread();

loop.exec(); // BLOCKING (non-busy) until quit() is called via the signal done()

While this is (in my eyes) clean code, this requires your netobject class to be a QObject and implement a signal done() (which is also cleaner than providing callbacks).

Now you can wrap this whole code in a function which will be a blocking call on itself, so it can return some results from your dialog if you want so.

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