blocks|key|4035305|text|您不应该等待事件处理程序中的输入。您需要重新考虑程序的逻辑，以便按预期的方式使用事件。如果返回到事件循环，则代码中的所有update()和repaint()调用都是不必要的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4035306|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

You shouldn't be waiting for input in your event handler. You need to rethink the logic of your program to use events the way they were intended. All the update() and repaint() calls in your code are unnecessary if you return to the event loop.

blocks|key|4035326|text|我使用睡眠来模拟计算机等待某件事发生的短暂时间。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4035327|正如我在问题中所说的，我不想使用事件，因为它是一大堆不必要的工作来完成非常简单的事情。|4035328|此外，程序继续运行所需的“事件”是USB事件。由于我使用的是HID类设备，因此无法在没有等待循环的情况下设置事件发生。USB+HID类不允许设置中断，操作系统声明该设备。|4035329|我设法让上面的内容正常工作。我浏览了调试器，注意到显示器将在休眠功能之前刷新。独立运行程序，我得到了随机的结果，显示刷新1%25的时间。我去掉了睡眠函数，并在它所在的位置添加了一些其他代码来模拟延迟，它很好。|4035330|每个人都知道，这是可能的，并不是禁止的，而且很容易做到以下几点：|4035331|qApp->processEvents();|code-block|syntax|javascript|4035332|qApp是QApplication标头中的全局外部变量。|4035333|因为这个USB事件使我的流程变得棘手，所以我偶然发现了QWaitCondition类。我打算启动一个等待USB事件的进程。我会一直等到进程释放等待条件，让我的例程继续。|4035334|但如果有人认为这是个坏主意，请直言不讳。我真的很感谢你的反馈，PiedPiper和敌意叉子。|4035335|谢谢。|4035336|entityMap^0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|10|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|11|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|12|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|13|8|@]|9|@]|A|$M|N]]|$1|O|3|P|5|6|7|14|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|15|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|16|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|17|8|@]|9|@]|A|$]]|$1|W|3|-4|5|6|7|18|8|@]|9|@]|A|$]]]|X|$]]

I was using sleep to emulate a brief amount of time the computer was waiting for something to happen. 

As I stated in my question, I didn't want to use events because it's a whole lot of unnecessary work to accomplish something extremely simply.

Also, the 'event' that needs to take place for the program to continue, is a USB event. Since I'm using an HID class device, there is no way to set an event to happen without a wait loop. USB HID classes don't permit setting interrupts, the OS claims the device. 

I managed to get the above to work. I walked through the debugger and noticed the display would refresh before the sleep function. Running the program independently, I got random results with the display refreshing 1% of the time. I got rid of the sleep function, and added some other code in it's place to emulate a delay, and it was fine. 

Just for everyone's knowledge, this is possible, it's not forbidden, and it's easy to do with the following: 

<pre><code>qApp-&gt;processEvents();
</code></pre>

qApp is a global external variable in the QApplication header.

Because this USB event is making my flow tricky, I stumbled upon the QWaitCondition Class. I was going to start a process waiting for the USB event. I would wait until the process releases the wait condition for my routine to continue. 

But if anyone thinks this is a bad idea, please, speak out. I really do appreciate your feedback PiedPiper and Hostile Fork.

Thank you.

blocks|key|1583563|text|如果我没记错的话，您有一个插槽，在这个插槽中，您更新了QLabel中显示的图像。但是您希望在插槽结束之前显示此更改。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1583564|如果是这种情况，则发出一个update()事件，并调用qApp->processEvents()。此方法处理在事件队列中等待的事件，然后返回，因此这可能就是您想要的。|1583565|PS:更新()可能根本不是必需的，我不确定。|1583566|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

If i understood correctly, you have a slot and in this slot, you update the image shown in a QLabel. But you want this change to be displayed before the slot finishes.

If that is the case, issue an update() event, and call qApp->processEvents(). This method processes events that are waiting in the event queue and then returns, therefore this may be what you are after.

PS: an update() may not be necessary at all, i am not sure.

blocks|key|1924844|text|我注意到，有时当你有多个分层的小部件，或者小部件内部的小部件时，调用它们的repaint()事件会很有帮助。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1924845|例如|1924846|this->repaint();
this->parentWidget()->repaint();
this->parentWidget()->parentWidget()->repaint();|code-block|syntax|javascript|1924847|这比将任何处理推送到另一个线程或创建额外的事件处理程序要容易得多。|1924848|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I noticed sometimes when you have multiple layered widgets, or widgets inside of widgets it helps to call their repaint() events.

For example

<pre><code>this-&gt;repaint();
this-&gt;parentWidget()-&gt;repaint();
this-&gt;parentWidget()-&gt;parentWidget()-&gt;repaint();
</code></pre>

This is far easier then pushing out any processing to another Thread, or creating additional event handlers.

I'm New to QT. I understand that you can force a display refresh, but I've pulled all my hair out trying to figure out how. Here is what I'm specifically trying to do.

I press a button (onClick signal event), which runs code that changes an image (QLabel) on the display, waits for input, and then proceeds by changing a new image (different QLabel). I've tried everything and the display doesn't refresh until the onclick signal event code is complete. Right now, I'm not waiting for user input, I'm using usleep(~500 ms) for testing purposes.

From what I read, QT is event driven meaning that I'm basically creating a bunch of events, that get put in a que, and executed when the (onClick signal event) returns to the (main loop)/(event handler). I don't want to wait until the function is complete, it's going to make programming extremely painful if I have to accomplish this routine entirely based on events.

How can I force the QLabel pixmap to refresh. I've tried everything. Below is all the code I have tried in my onClick signal event handler. (upButton is the name of the QLabel which is a pixmap)

<pre><code>update();
repaint();
ui-&gt;upButton-&gt;setUpdatesEnabled(TRUE);
update();
repaint();
QPaintEvent paintevent(ui-&gt;upButton-&gt;childrenRegion());
QPaintEvent * test = &amp;paintevent;
paintEvent(test);
this-&gt;changeEvent(test);
ui-&gt;upButton-&gt;update();
ui-&gt;upButton-&gt;repaint();
ui-&gt;upButton-&gt;repaint(ui-&gt;upButton-&gt;childrenRegion());
repaint();
QApplication::sendPostedEvents();
this-&gt;parentWidget()-&gt;update();
usleep(100000);
</code></pre>

As you can see, I'm just shooting in the dark at this point. I've tried to look at sample code and do all my homework, but I'm lost. Appreciate any help, advice, and or sample code.

QT Repaint/Redraw/Update/Do Something

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我是QT新手。我知道你可以强制刷新显示，但我已经想尽办法想办法了。这是我特别想要做的事情。我按下一个按钮(onClick signal event)，该按钮运行更改显示器上的图像(QLabel)的代码，等待输入，然后更改新图像(不同的QLabel)。我已经尝试了所有方法，直到onclick信号事件代码完成，显示才会刷新...

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